ABSTRACT This report describes the acquisition of deep-crustal multichannel seismic-reflection data in the Inner California Borderland aboard the R/V Maurice Ewing, conducted in October 1994 as part of the Los Angeles Regional Seismic Experiment (LARSE). LARSE is a cooperative study of the crustal structure of southern California involving earth scientists from the U.S. Geological Survey, Caltech, the University of Southern California, the University of California Los Angeles, and the Southern California Earthquake Center (SCEC). During LARSE, the R/V Ewing's 20- element air gun array, totaling 137.7 liters (8470 cu. in.), was used as the primary seismic source for wide-angle recording along three main onshore-offshore lines centered on the Los Angeles basin and the epicenters of the 1933 Long Beach and 1994 Northridge earthquakes. The LARSE onshore-offshore lines were each 200-250 km long, with the offshore portions being between 90 and 150 km long. The nearly 24,000 air gun signals generated by the Ewing were recorded by an array of 170 PASSCAL REFTEK recorders deployed at 2 km intervals along all three of the onshore lines and 9 ocean bottom seismometers (OBSs) deployed along two of the lines. Separate passes over the OBS-deployment lines were performed with a long air gun repetition rate (60 and 90 seconds) to minimize acoustic-wave interference from previous shots in the OBS data. The Ewing's 4.2-km, 160-channel, digital streamer was also used to record approximately 1250 km of 40-fold multichannel seismic-reflection data. To enhance the fold of the wide-angle data recorded onshore, mitigating against cultural and wind noise in the Los Angeles basin, the entire ship track was repeated at least once resulting in fewer than about 660 km of unique trackline coverage in the Inner Borderland. Portions of the seismic-reflection lines were repeated up to 6 times. A variety of other geophysical data were also continuously recorded, including 3.5 kHz bathymetry, multi- beam swath Hydrosweep bathymetry, magnetics, and gravity data. In this report, we describe the equipment and procedures used to acquire multichannel seismic-reflection and other geophysical data aboard the Ewing, provide a detailed cruise narrative, discuss the reduction of the data, and present near-trace constant offset seismic sections of the acquired profiles. CONTENTS Abstract 1 Introduction 3 Data Acquisition 4 Instrumentation on the Ewing 5 Ewing Cruise Narrative 8 Operations on the R/V Yellowfin 13 Data Processing 14 Description of the Data 14 Acknowledgments 15 References 16 Appendix 1. Abridged Ewing Air Gun Shot Times and Locations 19 Appendix 2. DMS-2000 Recording System 24 Appendix 3. Ewing Multichannel Seismic Reflection Tape Log 29 Appendix 4. EW-9415 Data Reduction Cruise Summary 47 Appendix 5. Software for Plotting Hydrosweep Multi-Beam Bathymetry Data 60 FIGURES Figure 1a. Map showing LARSE Seismic reflection lines and REFTEK stations 63 Figure 1b. Detail Map showing Ewing tracklines 64 Figure 2a. Individual passes of Ewing over Line 1 65 Figure 2b. Individual passes of Ewing over Line 2 66 Figure 3. R/V Ewing air gun deployment diagram 67 Figure 4. Detail of 20-element air gun array towed from R/V Ewing 68 Figure 5. Calculated source air gun wavelet 69 Figure 6. 3.5 kHz record across the Palos Verde fault 70 Figure 7. Constant-offset section for reflection Lines LARSE01R and LARSE02 71 Figure 8. Constant-offset section for reflection Lines LARSE03 and LARSE06 72 Figure 9. Constant-offset section for reflection Lines TR1, TR2, TR3 73 TABLES Table 1. R/V Ewing LARSE Line Start and End Times and Locations 17 Table 2. Sonobuoy Locations 18 Table 3. Ocean Bottom Seismometer Locations and Depths 18 INTRODUCTION The seismic earthquake hazards posed by blind thrust faults in southern California have been reported by a number of investigators [Stein and King, 1984; Stein and Yeats, 1989; Wright, 1991; Crouch and Suppe, 1993; Davis and Namson, 1994; Shaw and Suppe, 1994; Shaw et al., 1994]. Seismic-reflection methods are a valuable and necessary means of imaging the folding associated with blind thrusts, and have provided constraints for balanced cross sections used to map thrust ramps in the subsurface. Both the damaging 1971 San Fernando and 1994 Northridge earthquakes occurred on a blind thrusts [U.S. Geological Survey and the Southern California Earthquake Center, 1994]. This report describes shipboard operations on the R/V Maurice Ewing, leg EW-9415, including the acquisition of deep-crustal multichannel seismic-reflection data as part of the Los Angeles Regional Seismic Experiment (LARSE). LARSE is a cooperative study of the crustal structure of southern California involving scientists from the U.S. Geological Survey (USGS), Caltech, the University of Southern California, the University of California Los Angeles, and the Southern California Earthquake Center (SCEC). Seismic-reflection profiling in the greater Los Angeles area, 13-21 October, 1994, used the Ewing's 8470 cu. in. (137.7 liter) air gun array and 160-channel, 4.2-km digital streamer. The Ewing's air gun source was also recorded by 170 temporary land recorders (REFTEKs), the permanent southern California earthquake net, an array of 9 ocean-bottom seismometers deployed along two lines, and two successful sonobuoys. The Ewing fired nearly 24,000 air gun shots during the LARSE work. The Ewing, a 239' (72.8 m) long UNOLS vessel, formerly an industry seismic-reflection vessel, is operated by the Lamont- Doherty Earth Observatory. The R/V Ewing acquired several deep-crustal seismic-reflection profiles on the continental shelf of the Inner California Borderland, in the vicinity of Los Angeles, stretching from the 32o38'N to 34oN and from 119o45'W to 117o40'W (Figure 1a). At the heart of LARSE was the collection of three long onshore-offshore lines, Lines 1 to 3, which provided air gun signals for land recorders deployed along the projections of these lines. These lines include: (1) Line 1 trending N-S from the center of San Clemente Island through Seal Beach projecting into the 1933 Long Beach earthquake epicenter and the Mojave Desert, (2) Line 2 trending N-S along the western shores of San Clemente and Catalina Islands through Santa Monica projecting through the 1994 Northridge earthquake epicenter, and (3) Line 3 trending NE-SW from northwest of San Nicolas Island through the center of Los Angeles basin [Wright, 1991]. These three lines provide a regional reconnaissance of the crustal structure centered on the Los Angeles Basin: in addition they provide specific information about the crustal structure in the vicinity of two recent, damaging earthquakes in the greater Los Angeles region. Special care was taken to acquire large segments of these lines late at night (2300 L to 0500 L) [all local times given herein are Pacific Standard Time, which is 7 hours behind UTC], causing us to repeat parts of Lines 1 and 2 up to 5 times (Figures 2a and 2b). The planned ship track was altered throughout the cruise in order to maximize the acquisition of onshore-offshore data during late-night hours. Ocean bottom seismometers (OBS's) were deployed only along LARSE Lines 1 and 2. Shorter transit reflection lines, TR1, TR2, and TR3, connected LARSE Lines 1, 2 and 3 (sees Figure 1a and 1b). These transit lines were recorded in an oblique, fan geometry by the temporary and permanent onshore seismic stations. LARSE Line 3 was acquired between Lines 1 and 2 to provide enough time for the array of nine ocean bottom seismometers (OBSs) to be retrieved from along Line 1 and redeployed along Line 2 (Appendix 1). Upon completion of Line 2, the Ewing acquired reflection data along Line TR3 and then repeated the southern half of Line 1. The Ewing then acquired a series of short lines (Lines 4 and 6) crossing the Palos Verde and Newport-Inglewood faults while heading southeasterly towards San Diego, California (Appendix 1). Pre-cruise plans to shoot multichannel seismic (MCS) reflection lines in Santa Barbara Channel were abandoned because of the need to reshoot parts of Lines 1 and 2. No air gun shots were fired within the three-mile state limit for acoustic sources. Companion Open-file Reports describing the ocean-bottom seismometer and onshore recording of the LARSE air gun shots as well as the LARSE land refraction work using large chemical explosions are in preparation. DATA ACQUISITION Instrumentation on the Ewing Multichannel seismic-reflection profiling on the Ewing was performed using a 20-element, 137.7 liter (8470 cu. in.) air gun array (Figure 3 and 4) and a 160-channel, 4.2-km-long digital Digicon streamer. The air gun array, composed of Bolt air guns, was generally towed at depths between 8 and 10 meters. As shown in Figure 2, 8 guns were towed on each side of the ship from large retractable booms that are swung out abeam of the ship. The remaining four air guns were deployed from an A-frame on the stern of the ship. The ship-to-gun distance is staggered to minimize fouling the air guns and to optimally separate the air bubbles created by the air gun array: the center of the air gun array was towed approximately 39.6 m behind the stern of the ship (Figure 3). The width of the air gun array across the beam of the ship was roughly 33.8 m (111 feet) (see Figure 4). The Magnavox Global Positioning Satellite (GPS) receiver for the ship was located above the ship's bridge about 47.8 m forward of the stern of the ship, 87.4 m forward of the center of the air gun array. The sizes of the air gun chambers varied from 145 cu. in. (2.4 liters) to 875 cu. in. (14.2 liters) to provide a tuned outgoing source wavelet (Figure 4). Calculations of the source wavelet for this air gun array give a peak-to-peak pressure of 136.4 bar-meters and a primary/bubble ratio of 7.6 (Figure 5). Air gun shot times recorded in the navigation files were from the air gun fire command time determined from a Magnavox GPS clock. These shot times are considered accurate to within a millisecond. The air guns were generally fired during turns to permit the onshore recording of the air gun signals; air guns were shut off only when turning within the 3-mile state limit. For MCS profiling we used a 4.2 km, 160-channel digital seismic streamer built by Digicon. The streamer's group interval was 25 m and digitizers were located every 100 m (4 groups) along the streamer. The digital streamer data were telemetered to the Digicon DMS-2000 recording system after every shot (Appendix 2). The streamer was deployed directly behind the ship from its reel with the center of the first active section of the streamer located 187.5 m behind the center of the air gun array, 227.5 m behind the stern of the ship, and 275.3 m behind the ship's GPS receiver on the bridge (Figure 3). The streamer, having 19 depth control fins (birds) and a large tail buoy, was generally towed at a depth of 10 to 12 meters, depending on the sea-state conditions. The birds were Model 5010 manufactured by Digicourse, and incorporate pressure sensors. The pressure sensors provided depths along the streamer to the main lab and electronics within the birds automatically adjusted the bird fin angle (deviation from horizontal) to maintain the selected streamer depth. The streamer was positively buoyant during the cruise and the tail of the streamer (including the last 3 to 4 birds) tended to tow at a depth less than 10 to 12 meters. Appendix 2 describes the Digicon DMS-2000 recording system used to record the seismic- reflection data on the Ewing. We recorded 16-second record lengths with a 2-millisecond sample rate. At first the air gun array was triggered on distance every 50 meters along the tracklines. Because the record length plus 3 seconds (for system start-up overhead) cannot exceed the shotpoint interval with this recording system, we had to alter our air gun shooting schedule from distance to time (every 20 s) when strong currents caused an increase in ship's speed over the ground decreasing the shot time interval to less than 19 s. This change was made during Line 3 at 0353 UTC on JD 289. The Digicon DMS-2000 system recorded MCS data in SEG-D format on dual 3480 cartridge tape drives [Barry et al., 1975; SEG Subcommittee on Field Tape Standards, 1994]. After writing a tape in about 20 minutes, MCS data logging automatically switched over to a second tape drive, and the completed cartridge tape and cartridge label were ejected from the drive. Navigation data as well as information about the status of the MCS system were written to separate NAVLOG 3480 cartridge tapes (Appendix 2). 450 cartridge tapes containing MCS data were written during leg EW94-15. ProMAX software running on a Sun SPARCstation reformatted the SEG-D tapes into SEG-Y format, transcribing the 3480 cartridge tapes onto 2-Gbyte Exabyte tape. An approximate 5:1 tape compression resulted in 80 Exabyte SEG-Y tapes (see Appendix 3). Appendix 3, which was largely completed at sea, also provides a list of shots that were not recorded by the DMS-2000 system and the 3480 cartridge tapes that could not be read by the ProMAX system onboard the Ewing. Under every Exabyte tape, Appendix 3 provides a table showing the 3480 cartridge tape numbers written to the Exabyte tape, the Field File Identification numbers (FFID), and the corresponding shot-point number for each FFID written to Exabyte tape. Appendix 3 is thus an inventory of the data stored on both the original SEG-D 3480 cartridge tapes and the SEG-Y Exabyte tape copies. ProMAX seismic data processing software was used to monitor the recorded seismic- reflection data quality in near real-time. This software, installed on a Sun SPARCstation, was primarily used to visually inspect every 50th shot gather as well as to transcribe the SEG-D data from 3480 cartridges into SEG-Y format on Exabyte tape format. Limited segments of the lines were also plotted as a constant offset section to monitor data quality. Acquisition of multichannel seismic-reflection data on the Ewing was controlled by several personal computers (PCs) that each monitored a different aspect of the acquisition system. For every shotpoint separate PCs provided a record of the error of the firing time for each air gun (errors less than 1 msec were specified), the air gun depth, the bird depth and fin angle, the streamer depth, signal levels on every fourth channel of the streamer, and the data-file number and shot number for every shot. Sun workstations were used to log other geophysical data (Appendix 2). Navigation on the Ewing was based on redundant Magnavox GPS receivers operated in selected availability mode: the GPS locations were smoothed over a ten-minute window and updated using the Furuno course and speed log. This navigation was written to a separate 3480 cartridge tape and is estimated to be accurate to within 25 meters. Files containing air gun origin times and final air gun locations were sent from the Ewing via e-mail to all LARSE investigators on a daily basis. These origin times were used to examine the quality of data recorded onshore by the three deployments of REFTEK arrays. The reduction and playback of wide-angle data during the field experiment were instrumental for the decision to repeat Line 1 to insure that this line was reshot during late-night hours. Communication with other LARSE personnel was by cellular phone. Fifteen model 53B expendable military sonobuoys were launched during the cruise, almost entirely on Line 3. Only two sonobuoys functioned properly, however, these sonobuoys yielded useful records to distances as much as 30 km (Table 2). The successful buoys were dropped by hand from the end of the portside air gun boom. No successful buoys were launched from the sonobuoy launcher. The first successful buoy was launched on the outbound leg of Line 3. The second successful buoy was launched near the intersection of Lines 2 and 3, and was recorded during Lines 03R, TR2, and 02. All buoys were programmed to release their hydrophone to a depth of 90 feet and to broadcast for 8 hours before scuttling. Several other kinds of data were continuously recorded on the Ewing including navigation, magnetics, gravity, 3.5 kHz bathymetry, Hydrosweep swath bathymetry, and sea-surface temperature data (see Appendix 4). The quality of the 3.5 kHz echo sounder data is considered to be excellent, and provides abundant evidence for recent faulting in the offshore (Figure 6). Magnetic-anomaly data were continuously recorded using a Varian V75 magnetometer towed behind the ship. Gravity data were acquired using KSS-30 and BGM-3 gravimeters (Appendix 4). Appendix 4 describes the format of the daily files created for each of the data types, and indicates when data were not acquired for each of the instruments. Appendix 5 describes how the digital Hydrosweep data can be plotted as maps of seafloor depth or seafloor reflectance. Ewing Cruise Narrative The Ewing left her berth at Long Beach Harbor at 1516 UTC on Julian Day (JD) 286 (0816 L on 13 October 1994). She then steamed to a location several miles southeast of the first way point at the northern end of Line 1 just south of the Long Beach harbor entrance. Upon reaching this way point the 8470 cu. in. air gun array was immediately deployed. Because of the heavy ship traffic at this location, the MCS streamer was not deployed on this first pass along Line 1. The first pass of Line 1 (LA01) was designed only as a source for the OBS's and onshore recorder array. It was collected using a 60-second air gun repetition rate to minimize water-wave arrivals on the OBS records. LA01 commenced at 1830 UTC (1130L) and the ship was on course for Line 1 at 1849 UTC on JD 286 (1149 L on 13 October 1994). Without towing the streamer, the Ewing was able to start shooting the line northeast of the coastwise shipping lane and to transit between oil platforms in the separation zone of the shipping lane. The offshore portion of Line 1 runs about 84 km from the commercial anchorage south of Seal Beach to the three-mile limit off the center of San Clemente Island (Figure 2a). After completing the first OBS pass of Line 1 at the three-mile limit of San Clemente Island, the ship turned easterly to deploy the streamer at approximately 0600 UTC on JD 287 (2300L of 13 October 1994). During the deployment of the streamer a number of sections were pumped with oil to properly ballast the streamer. We also changed one failed compass section in the new, front part of the streamer. The replacement compass section, however, also failed to work. Only the compass sections in the older part of the streamer near the tail, having digitizing cans, properly functioned during the cruise. As the streamer was deployed, the depth control fins (birds) were attached one by one and checked to insure they were functioning properly. The streamer was completely deployed by 1155 UTC on JD 287 (0455 L on 14 October 1994) and Line 01R was commenced (Fig. 1a). After transiting westward to the southernmost way point for Line 1 north of San Clemente Island, the Ewing completed an inside turn and MCS data acquisition on Line 1R northbound commenced at about 1600 UTC JD 287 (0900L on 14 October). Line 1R had to deviate northwest of the oil platforms and therefore the northeastern end of the line was not exactly along the Line 1 onshore-offshore profile (Figs. 1a and 2a). After Line 1 was acquired for both the OBS and multichannel-seismic-reflection (MCS) passes (LA01 and LARSE01R respectively), wide-angle data from a few onland REFTEK recorders were downloaded for examination. Failure to observe individual air gun pops in these wide-angle data prompted the decision to reshoot the northeast end of Line 1, closest to Long Beach, along two additional transits to insure that this portion of the line would be recorded at least once during the late-night hours. Thus, two short sections of Line 1 using 50-m shot intervals were repeated between the north easternmost way point and Catalina Island (these were named LARSE01X for the south directed line and LARSE01Y for the north directed line (Fig. 2a)). Line LARSE01Y was acquired during the night from 0632 UTC to 1235 UTC on JD 288 (2332 L until 0535 L on 15 October 1994). While acquiring Lines 01X and 01Y we learned that OBS6 from the first OBS deployment had not been recovered, however, all the other 8 OBS's were recovered and yielded useful data. OBS6 was recovered by an unrelated vessel on 19 October 1994, during acquisition of Line 02Z. After completing 4 repeats of Line 1 (LA01, LARSE01R, LARSE01X, and LARSE01Y), the Ewing made an inside turn onto LARSE transit Line TR1 at 1235 UTC on JD 288 (0535 L on 15 October 1994). Shortly after starting this line, however, the entire streamer rose to the surface and the streamer tension exceeded the usual upper limit of 3500 lbs. Fearing that the streamer had become tangled with gear or kelp, the Ewing quickly lowered its speed through the water and the Ewing's Zodiac was sent to inspect both the tail buoy and those birds that had risen to the surface. At the same time, the first several sections of the streamer were pulled in and lead foil was wrapped around each section to make the head of the streamer heavier. The Ewing's Zodiac removed a great deal of kelp that had been caught in the tail buoy but found none in the birds. The Ewing's speed was increased and the streamer was found to fly at the proper attitude and depth once again. This problem resulted in the loss of most of the data along the strike of San Pedro Basin during the LARSE transit Line TR1, and seriously degraded the easterly line to this basin from the northern end of Line 1. Data quality from the NE-SW-trending segment of TR1 from the San Pedro Basin to the landward end of Line 3, however, was satisfactory. An inside turn was made onto Line 3. Two passes of the NE-SW-trending Line 3 (LARSE03 and LARSE03R) were made without incident and with little nearby ship traffic. The two passes required nearly 29 hours between 2146 UTC on JD 288 and 0225 UTC on JD 290 (Table 1). To reclaim the time lost to the streamer problem on TR1, Line 3 was shortened by about 18 km, making the line approximately 122 km long. Each pass was collected with an air gun repetition rate of either 50 m or 20 seconds and was recorded with the multichannel streamer. At the completion of Line 3, we made an inside turn onto transit Line TR2, which was slightly deviated to the west from our pre-cruise plan to avoid a restricted area in the vicinity of Los Angeles Airport where sewer lines extend offshore. TR2 was completed at 0458 UTC on JD 290. We next carried out five passes on the 150-km long, N-S-trending Line 2 (Table 1). Upon reaching the start of Line 2 at its northern end, the air gun array was turned off as we performed a wide turn within the 3-mile state limit south of Malibu. This turn was completed at approximately 0551 UTC on JD 290 (2251 L on 16 October 1994). MCS data along Line 2 were first acquired using a shot interval of 50 meters ending at 0147 UTC on JD 291 (1847 L 17 October 1994). A 180o turn back onto Line 2 was completed at 0156 UTC on JD 291 (1856 L on 17 October 1994) at the southern end of the line. The 8 remaining OBSs were deployed along this line during our first pass of the line (Line LARSE02); they were programmed to start recording at 1900 L on 17 October 1994. The second, OBS pass of Line 2 (Line LARSE02R) used a 90-sec air gun repetition rate to minimize water-wave arrivals on the OBS data (Fig. 2b). We also continued recording data with the multichannel streamer. The first two passes along Line 2 were completed without serious incident, although in the daylight hours of 18 October 1994 we noted that a small float had been snagged by a bird about 1/3 of the length of the streamer behind the ship. Our chase boat following the tail buoy was able to cut the float away from the streamer. The 3-mile limit and northern end of the OBS pass of Line 2 was reached at 1955 UTC on JD 291 (1255 L on 18 October 1994) and the air guns were turned off at that time. After another wide-turn within the 3- mile state limit, acquisition of a third pass of the northern end of the line (Line LARSE02X) commenced at 2103 UTC on JD 291 (1403 L 18 October 1994). At 0400 UTC on JD 292 (2100 L 18 October 1994) this southerly pass was completed and the ship made another 180o turn to record Line LARSE02Y during nighttime hours while steaming towards the north (Fig. 2b). The Ewing reached the 3-mile limit completing Line LARSE02Y at 1200 UTC on JD 292 (0500 L 19 October 1994). The Ewing made a final wide turn within the 3-mile limit with air guns off to begin Line LARSE02Z. The fifth and last pass along Line 2, Line LARSE02Z, was started at 1230 UTC on JD 292 (0530 L 19 October 1994) and was completed as far south as Line TR3 by 1800 UTC on JD 292 (1100 L 19 October 1994). The Ewing made an inside turn onto Line TR3 (Figure 1b). Line TR3, a 49-km long line connecting Lines 1 and 2 along the center of San Pedro Basin, was completed in 6 hours at 2350 UTC on JD 292 (1650 L 19 October 1994). At this time the Ewing made an inside turn to reshoot Line 1 southwards towards San Clemente Island at the request of the LARSE team recording wide-angle data on land (Fig. 2a). This southerly transit of Line 1 (Line LARSE01A) was completed in 6 hours at 0640 UTC on JD 293 (2340 L 20 October 1994), and the Ewing turned 180o to reshoot Line 1 northwards towards Long Beach (Line LARSE01B, see Fig. 2a). The reshooting of Line 1 was completed 8 hours later at 1355 UTC on JD 293 (0655 L 20 October 1994). After reshooting Line 1 (along Line LARSE01B), we began a series of zig-zag lines to image the Palos Verde and Newport-Inglewood fault systems while transiting southeasterly in the direction of San Diego. The first of these lines, Line LARSE04, trending ENE-WSW, was started at 1400 UTC on JD 293 (0700 L on 20 October 1994). Shortly thereafter, at 1445 UTC (0745 L), the rudder and propeller of the chase boat, Ventura, became snared in our multichannel streamer during the turn to Line LARSE04. The Ewing's Zodiac was launched in an attempt to free the chase boat, Ventura, but to no avail. At 1630 UTC we slowed the Ewing and turned off the air guns in an attempt to free the Ventura, effectively ending Line LARSE04. A dive boat freed the chase boat at 1700 UTC (1000 L) without damage to either boat. When retrieving the streamer at the end of the MCS data acquisition, we found that the chase boat's propeller damaged the last two sections of the streamer. Line LARSE05 was attempted but was aborted due to equipment failure. A very clear 3.5 kHz record of the Palos Verde fault on Line LARSE04 shows roughly 40 m of recent offset on a steeply dipping scarp (Figure 6). After turning within the 3-mile-limit with our air guns off, MCS profiling on Line LARSE06a, parallel to Line 4 but located about a mile south of Line LARSE04, started at 1835 UTC (1135 L). Line LARSE06a was designed to image the Palos Verde fault system at depth. Line LARSE06a was completed in about 3 hours at 2128 UTC on JD 293 (1428 L on 20 October). An inside turn was made onto Line LARSE06b. Line LARSE06b, trending E-W, also designed to cross the Palos Verde fault, was completed in about 6 hours at 0231 UTC on JD 294 (1916 L on 20 October). A final inside turn was made onto Line LARSE06c. Our final line, Line LARSE06c, ran NW-SE about 4 miles seaward of the coastline and was designed to image a regional detachment surface first identified by Crouch and Suppe (1993). Line LARSE06c was ended after 2 hours at 0433 UTC (2133 on 20 October 1994) . During Line LARSE06c, at approximately 0330 UTC on JD 294 (2030 L on 20 October 1994), the chase boat attempted but failed to transfer two members of the science party (Rob Clayton and John McRaney) involved with the upcoming onshore explosive survey for LARSE. At 0433 UTC on JD 294 (2130 L on 20 October 1994) we began to bring the air gun array and the streamer aboard. After the equipment was retrieved and secured on deck in about 4 1/2 hours, about 0900 UTC on JD 294 (0200 L on 20 October), we transited to port at San Diego. The Ewing arrived at port at San Diego at about 1446 UTC on JD 294 (0746 L on 21 October 1994) and main engines were secured at 1630 UTC on JD 294 (0930 L on 21 October 1994). Weather conditions for the survey were generally ideal. The prevailing weather pattern consisted of calm to light winds in the late evening to early morning hours with winds picking up strength in the afternoon and early evening hours reaching highs of more than 15 knots. The highest winds (30 knots) were encountered during a storm during the first two passes of Line 1 (Lines 01 and 01R). Operations on the R/V Yellowfin Nine ocean bottom seismometers (OBS's) were deployed and recovered by the R/V Yellowfin, a 76-foot vessel operated by the Ocean Studies Institute, a consortium of universities in Southern California, and based in San Pedro, California. Seven OBS's used during LARSE were operated by the USGS Branch of Atlantic Marine Geology and the two other OBS's were loaned for the LARSE experiment by Dalhousie University, Halifax, Nova Scotia. Separate OBS deployments were made along Lines 1 and 2 to provide control on the shallow crustal velocities along these lines (Figure 1b and Table 3). Each OBS deployment recorded air gun signals only along the line on which it was deployed. The OBS's were concentrated on the northern ends of these lines, to help resolve the velocity structure nearest the Los Angeles Basin. OBS 8 on the Line 2 deployment was deployed to the southwest of San Clemente Island in an attempt to record reversed upper mantle refractions (Pn). Nine OBS's along Line 1 were deployed on 12 October 1994 after being programmed to begin recording at 1600 UTC on JD 286 (0900 L on 13 October 1994). These OBSs recorded during both OBS and MCS passes of Line 1 (Lines LA01 and LARSE01R) made by the Ewing, and were recovered in the night and morning of 14-15 October 1994. Eight OBS's were immediately recovered from this deployment and all 8 provided useful data for Lines LA01 and LARSE01R (as well as for part of Line 1X): OBS 6 of this deployment was found floating at the surface after being lost for about 4 days. This OBS did not stay attached to its anchor and released shortly after impacting the seafloor, recording only 10 shots of Line LA01. The remaining eight OBS's were deployed along Line LARSE02 between 0900 and 1800 UTC on JD 290 (0200 and 1100 L on 17 October 1994), and were programmed to begin recording at 0200 UTC on JD 291 (1900 L on 18 October 1994). The OBS's were recovered between 0215 and 1420 UTC on JD 292 (night and morning of 19-20 October) and thus recorded both OBS and MCS passes of Line 2 (Lines LARSE02R and LARSE02X); four OBS's recorded at least part of MCS Line LARSE02Y (Table 1). OBS 3, deployed at the intersection of Lines 2 and 3, and OBS 5, deployed south of Catalina (Table 3), were not immediately recovered from this deployment. Both were found floating at the sea surface after the LARSE MCS experiment ended. OBS 5 recorded 100 shots (12%) of Line LARSE02R before it released prematurely. OBS 3 stayed on the seafloor for nearly a day, and recorded 550 shots of Line LARSE02R (representing 66% of the line). OBS 7 from this deployment failed to record any useful data (Table 3). The total OBS data recovery rate for both deployments was about 80%. The premature releases of the OBS's were caused by a manufacturing error in the coupling springs between the OBS's and their bottom weight. DATA PROCESSING As described in Appendix 3, two channels from the streamer were directly written onto the navigation (NAVLOG) 3480 cartridge tapes during our leg, a near-trace (ch. 150) and a far-trace (ch. 10). After the cruise we plotted constant offset sections for all lines using the near-trace, ch. 150, located 412.5 meters behind the center of the air gun array. Processing of these data included: (1) bandpass filter from 4-8-48-60 Hz, (2) automatic gain control (AGC), using a 500- msec window, (3) a water-bottom mute (to eliminate water column noise), and (4) display. DESCRIPTION OF THE DATA The constant offset sections indicate the multichannel seismic-reflection data are of high quality (Figures 7-9). The sections image a number of important deformation structures in the San Pedro, Catalina, and San Nicolas Basins. Folding of the sediments south of Long Beach in San Pedro basin is well-displayed on Line 1. Line 2 imaged a relict fault south of San Clemente ridge. Line 2 also reveals that Catalina Basin is underlain by a buried basement high that trends northwest and appears to bound an active fault. Block tilting of the Santa Catalina Ridge and Pilgrim Banks is clearly shown in these profiles. Prominent multiples were generated over the hard basement outcrops such as Santa Catalina Ridge. Several orders of multiples, which were not suppressed by any of the processing used here, are evident. No reflections beneath the sedimentary basins are observed in the constant offset sections, so they have been plotted to a depth of 6 seconds only. No lower crustal reflections were observed in these unstacked data. ACKNOWLEDGMENTS We thank the Captain, crew, and Ewing-based science party, in particular Bruce Francis, Science Officer, Stefanus Budhypramono, System operator, Chuck Donaldson, ET, and Johnny DiBernardo, Chief Air Gunner, for their excellent and hard work as well as their hospitality during our leg. Mike Rawson of Lamont-Doherty Earth Observatory (LDEO) patiently answered many questions about the Ewing prior to the cruise. The US Coast Guard issued a Notice to Mariners and helped inform vessels of our activities. The US Navy granted permission to enter waters in their jurisdiction on the western end of Line 3. The Los Angeles Fisherman's Association notified their members of our activities. Peter Buhl of LDEO was a valuable resource aboard the Ewing during the cruise. Jim Vaughan, USGS, provided the military sonobuoys. Greg Miller, Uri ten Brink, and Doug Foster of the USGS and the Captain of the R/V Yellowfin kept us up-to-date on the status of the OBS deployments. Gary Fuis, USGS, Tom Henyey, USC, and David Okaya, USC, helped to plan and direct our operations at sea. Jon Childs arranged for the ProMAX system used to transcribe the 3480 cartridges. We thank the IRIS/PASSCAL facility (at Stanford) for providing the REFTEK instruments used in this experiment. Joe Jackson videotaped our work on the Ewing. Pat Jorgensen and Jim Mori, both of the USGS, arranged a press conference the day before the cruise. John Pittman of Vessel Assist Cabrillo of San Pedro provided a chase boat for Line 2. Beth Ambos, CSLB, and family provided lodgings to T.M. Brocher prior to the cruise. Jon Childs, USGS, wrote Appendix 2. Stefanus Budhypramono, LDEO, wrote Appendix 4. Gary Fuis, USGS, drafted Figures 1a and 1b, modified here. Bruce Francis, LDEO, drafted Figures 2 and 3, modified here. Pat Hart provided useful comments on an earlier draft of this report and generated Figure 5. This work was supported by the National Earthquake Hazards Reduction Program, the National Science Foundation, and the Southern California Earthquake Center. REFERENCES CITED Barry, K.M., D.A. Cravers, and C.W. Kneale, 1975, Recommended standards for digital tape formats: Geophysics, v. 40, p. 344-352. Crouch, J.S., and J. Suppe, 1993, Late Cenozoic tectonic evolution of the Los Angeles basin and inner California borderland: A model for core complex-like crustal extension, Geological Society of America, Bulletin, v. 105, p. 1415-1434. Davis, T.L. and J.S. Namson, 1994, A balanced cross-section of the 1994 Northridge earthquake, southern California, Nature, v. 372, p. 167-169. Shaw, J.H., S.C. Hook, and J. Suppe, 1994, Structural trend analysis by axial surface mapping, AAPG Bulletin, v. 78, p. 700-721. Shaw, J.H., and J. Suppe, 1994, Active faulting and growth folding in the eastern Santa Barbara Channel, California, Geol. Society of America, Bulletin, v. 106, p. 607-626. Stein, R.S., and G.C.P. King, 1984, Seismic potential revealed by surface folding: 1983 Coalinga, California, earthquake, Science, v. 224, p. 869-872. Stein, R.S., and R.S. Yeats, 1989, Hidden earthquakes, Scientific American, June 1989, p. 48- 57. Wright, T., 1991, Structural geology and tectonic evolution of the Los Angeles Basin, California, in K.T. Biddle, ed., Active margin basins: AAPG Memoir 52, p. 35-134. SEG Subcommittee on Field Tape Standards, 1994, Digital field tape format standards - SEG-D, Revision 1, Geophysics, v. 59, p. 668-684. U.S. Geological Survey and Southern California Earthquake Center, 1994, The magnitude 6.7 Northridge, California, earthquake of 17 January 1994, Science, v. 266, p. 389-397. TABLE 1. R/V Ewing LARSE Line Start and End Times and Locations _________________________________________________________________________ Start of Line End of Line Line UTC Lat. (N) Long. (W) UTC Lat. (N) Long. (W) No. Day:HrMn Deg. Min. Deg. Min. Day:HrMn Deg. Min. Deg. Min. 01 286:1849 33 38.191 118 07.055 287:0541 32 56.869 118 25.333 01R 287:1155 33 49.475 118 07.194 288:0124 33 37.276 118 11.621 01X 288:0128 33 36.951 118 11.505 288:0632 33 15.103 118 15.692 01Y 288:0632 33 15.091 118 15.704 288:1235 33 35.179 118 12.782 TR1 288:1236 33 35.125 118 12.855 288:2144 33 49.777 118 30.522 03 288:2145 33 49.768 118 30.569 289:1210 33 28.300 119 42.396 03R 289:1211 33 28.308 119 42.303 290:0237 33 51.075 118 27.880 (03R 289:1211 33 28.308 119 42.303 290:0225 33 50.479 118 28.323) TR2 290:0238 33 51.147 118 27.950 290:0459 33 59.144 118 35.305 (TR2 290:0239 33 51.171 118 27.983 290:0458 33 59.118 118 35.302) 02 290:0517 34 00.507 118 35.383 291:0154 32 38.305 118 43.391 (02 290:0551 33 59.170 118 34.841 291:0147 32 37.892 118 43.487) 02R 291:0155 32 38.363 118 43.386 291:1956 33 59.187 118 35.040 (02R 291:0156 32 38.444 118 43.387 291:1955 33 58.784 118 35.080) 02X 291:2052 33 58.996 118 34.911 292:0404 33 26.080 118 40.439 (02X 291:2103 33 58.203 118 35.002 292:0359 33 26.440 118 40.279) 02Y 292:0405 33 26.060 118 40.465 292:1231 33 59.090 118 35.130 (02Y 292:0406 33 26.008 118 40.505 292:1232 33 58.991 118 35.033) 02Z 292:1329 33 59.209 118 34.984 292:1750 33 41.121 118 37.782 (02Z 292:1336 33 58.754 118 35.088 292:1743 33 41.548 118 38.042) TR3 292:1751 33 41.082 118 37.708 292:2349 33 25.458 118 11.820 (TR3 292:1753 33 41.043 118 37.614 292:2350 33 25.454 118 11.805) 01A 292:2351 33 25.314 118 11.858 293:0640 32 58.774 118 23.739 (01A 292:2352 33 25.218 118 11.890 293:0558 33 00.418 118 23.248) 01B 293:0640 32 58.815 118 23.759 293:1356 33 28.895 118 10.714 (01B 293:0630 32 58.610 118 23.032 293:1355 33 28.797 118 10.739) 04 293:1400 33 29.156 118 10.808 293:1644 33 32.535 118 02.362 (04 293:1355 33 28.797 118 10.739 293:1630 33 32.385 118 02.975) 05 293:1712 33 32.892 118 00.680 293:1835 33 32.842 117 56.077 06a 293:1837 33 32.829 117 56.121 293:2128 33 29.735 118 09.673 06b 293:2147 33 28.663 118 09.354 294:0231 33 24.877 117 46.034 06c 294:0242 33 24.300 117 45.355 294:0433 33 17.037 117 41.468 _________________________________________________________________________________________ Parens indicate times and locations noted in MCS log aboard ship; other times and locations taken from digital shot log provided by Stephanus Budhypramono of LDEO. TABLE 2. Sonobuoy Locations _________________________________________________________________________ Launch Time and Location Sono- MCS Water buoy Line UTC Lat. (N) Long. (W) File Temp. Drift No. No. Day:HrMn Deg. Min. Deg. Min. No. (ūC) (knots) 01 03 289:0100 33 44.7679 118 46.9194 648 18.7 02 03R 290:0046 33 48.1 118 36.2 2289 18.1 0.5 _________________________________________________________________________ TABLE 3. Ocean Bottom Seismometer Locations and Depths ____________________________________________________________________________ Line 1 Station OBS Line 01R Latitude (N) Longitude (W) Depth Name Number FFID Deg. Min. Deg. Min. (m) OBS1 A3 2217 33 34.0844 118 08.7095 97 OBS2 A1 2107 33 31.1492 118 09.8185 321 OBS3 A2 1926 33 26.5097 118 11.5804 723 OBS4 DAL A 1713 33 21.0082 118 13.4897 711 OBS5 DAL C 1549 33 16.8277 118 15.1957 177 OBS6* C1 1387 33 12.8067 118 16.5421 1134 OBS7 C9 1137 33 06.7002 118 20.1462 1158 OBS8 C4 904 33 01.0848 118 23.2386 798 OBS9 C3 722 32 56.3934 118 25.2850 1191-1196# Line 2 Station OBS Line 02 Latitude (N) Longitude (W) Depth Name Number FFID Deg. Min. Deg. Min. (m) OBS1 C4 124 33 58.6342 118 34.9445 77 OBS2 C3 337 33 53.0789 118 36.0271 79 OBS3* C9 532 33 47.8420 118 37.0280 833 OBS4 A1 720 33 42.9050 118 37.8090 705 OBS5* A2 1010 33 35.2470 118 39.3110 618 OBS6 A3 1511 33 21.9648 118 40.6503 1200 OBS7$ DAL C 1868 33 12.4439 118 41.3244 1330-1340# OBS8 DAL A 2510 32 55.2289 118 42.5562 1210-1215# ______________________________________________________________________________ *OBS was not immediately recovered but was found drifting a few days after the others were retrieved. #The depth-sounder on the Yellowfin could not provide more accurate readings at these depths. $Failed to record any useful data. APPENDIX 1: Abridged Ewing Shot Times and Locations Year:Date:Hr:Min:Sec FFID Lat. Long. Line Number 94+286:18:49:17.736 00101 N 33 38.1910 W 118 07.0551 LA01 94+286:19:00:18.473 00112 N 33 37.5247 W 118 07.3583 LA01 94+286:20:00:18.483 00172 N 33 33.7540 W 118 08.9776 LA01 94+286:21:00:20.715 00232 N 33 29.8386 W 118 10.2979 LA01 94+286:22:00:21.955 00292 N 33 25.8759 W 118 11.6982 LA01 94+286:23:00:24.907 00352 N 33 21.7805 W 118 13.1994 LA01 94+287:00:00:28.404 00412 N 33 17.8508 W 118 14.5750 LA01 94+287:01:00:29.640 00472 N 33 14.2768 W 118 16.2731 LA01 94+287:02:00:30.687 00532 N 33 10.7990 W 118 18.2605 LA01 94+287:03:00:31.687 00592 N 33 07.0360 W 118 20.1193 LA01 94+287:04:00:34.916 00652 N 33 03.3934 W 118 22.0520 LA01 94+287:05:00:36.116 00712 N 32 59.5526 W 118 23.9744 LA01 94+287:05:41:37.305 00753 N 32 56.8693 W 118 25.3331 LA01 94+287:11:55:42.459 00105 N 32 49.4752 W 118 07.1937 LARSE01R 94+287:12:00:08.057 00118 N 32 49.6061 W 118 07.5666 LARSE01R 94+287:13:00:03.960 00297 N 32 51.5937 W 118 12.7275 LARSE01R 94+287:14:00:20.228 00474 N 32 53.6265 W 118 17.7704 LARSE01R 94+287:15:00:10.140 00644 N 32 55.3614 W 118 22.7083 LARSE01R 94+287:16:00:18.452 00806 N 32 58.6314 W 118 24.5302 LARSE01R 94+287:17:00:03.958 00979 N 33 02.8678 W 118 22.2462 LARSE01R 94+287:18:00:19.628 01154 N 33 07.1215 W 118 20.0302 LARSE01R 94+287:19:00:18.668 01323 N 33 11.2740 W 118 17.8620 LARSE01R 94+287:20:00:20.480 01495 N 33 15.4655 W 118 15.6491 LARSE01R 94+287:21:00:03.943 01666 N 33 19.8046 W 118 13.8989 LARSE01R 94+287:22:00:11.184 01838 N 33 24.2134 W 118 12.3503 LARSE01R 94+287:23:00:00.920 02011 N 33 28.6400 W 118 10.7141 LARSE01R 94+288:00:00:08.128 02186 N 33 33.2089 W 118 10.7523 LARSE01R 94+288:01:00:02.001 02353 N 33 37.0877 W 118 12.6862 LARSE01R 94+288:01:24:01.118 02414 N 33 37.2756 W 118 11.6212 LARSE01R 94-288:01:28:30.803 00101 N 33 36.9514 W 118 11.5048 LARSE01X 94+288:02:00:05.743 00174 N 33 34.5805 W 118 11.0279 LARSE01X 94+288:03:00:20.624 00339 N 33 30.2560 W 118 10.1924 LARSE01X 94+288:04:00:17.875 00513 N 33 25.7471 W 118 11.6947 LARSE01X 94+288:05:00:13.976 00684 N 33 21.3779 W 118 13.3172 LARSE01X 94+288:06:00:21.627 00854 N 33 17.0405 W 118 14.8050 LARSE01X 94+288:06:32:37.925 00935 N 33 15.1029 W 118 15.6916 LARSE01X 94+288:06:32:56.018 00101 N 33 15.0910 W 118 15.7035 LARSE01Y 94+288:07:00:18.578 00153 N 33 14.5518 W 118 16.9116 LARSE01Y 94+288:08:00:18.152 00314 N 33 17.4955 W 118 14.6791 LARSE01Y 94+288:09:00:17.824 00478 N 33 21.7296 W 118 13.3686 LARSE01Y 94+288:10:00:21.044 00644 N 33 25.9674 W 118 11.7275 LARSE01Y 94+288:11:00:17.286 00814 N 33 30.2943 W 118 10.0756 LARSE01Y 94+288:12:00:04.803 00976 N 33 34.5261 W 118 11.0721 LARSE01Y 94+288:12:35:17.847 01068 N 33 35.1791 W 118 12.7817 LARSE01Y Line TR1a 94-288:12:36:27.396 00101 N 33 35.1254 W 118 12.8549 LARSETR1 94+288:13:00:07.504 00167 N 33 33.8226 W 118 14.2356 LARSETR1 94+288:14:00:03.490 00322 N 33 30.7704 W 118 17.3762 LARSETR1 94+288:14:30:28.903 00393 N 33 30.2095 W 118 19.3732 LARSETR1 Line TR1b 94-288:17:47:10.731 00101 N 33 34.3285 W 118 31.1544 LARSETR1 94+288:18:00:08.860 00138 N 33 35.1506 W 118 31.8033 LARSETR1 94+288:19:00:01.583 00312 N 33 39.4213 W 118 33.4989 LARSETR1 94+288:20:00:02.447 00488 N 33 43.8144 W 118 31.5320 LARSETR1 94+288:21:00:19.953 00663 N 33 48.1076 W 118 29.3360 LARSETR1 94+288:21:44:45.676 00783 N 33 49.7766 W 118 30.5224 LARSETR1 94+288:21:45:16.921 00101 N 33 49.7675 W 118 30.5687 LARSE03 94+288:22:00:18.422 00145 N 33 49.4030 W 118 31.9168 LARSE03 94+288:23:00:12.138 00314 N 33 47.9471 W 118 36.9643 LARSE03 94+289:00:00:00.042 00476 N 33 46.3380 W 118 41.7889 LARSE03 94+289:01:00:12.994 00648 N 33 44.7615 W 118 46.9474 LARSE03 94+289:02:00:09.955 00817 N 33 43.3139 W 118 52.1335 LARSE03 94+289:03:00:08.048 00996 N 33 41.5772 W 118 57.5282 LARSE03 94+289:04:00:05.970 01184 N 33 40.0384 W 119 03.2405 LARSE03 94+289:05:00:17.889 01362 N 33 38.2112 W 119 08.4451 LARSE03 94+289:06:00:11.771 01537 N 33 36.8048 W 119 13.7917 LARSE03 94+289:07:00:21.272 01713 N 33 35.2201 W 119 19.0487 LARSE03 94+289:08:00:11.164 01873 N 33 33.8611 W 119 23.8832 LARSE03 94+289:09:00:22.406 02036 N 33 32.2860 W 119 28.7390 LARSE03 94+289:10:00:16.666 02200 N 33 30.6818 W 119 33.6381 LARSE03 94+289:11:00:04.329 02367 N 33 29.4110 W 119 38.7410 LARSE03 94+289:12:00:13.780 02524 N 33 28.6629 W 119 43.0103 LARSE03 94+289:12:10:24.907 02546 N 33 28.3001 W 119 42.3963 LARSE03 94+289:12:11:30.943 00101 N 33 28.3078 W 119 42.3029 LARSE03R 94+289:13:00:09.192 00230 N 33 29.4439 W 119 38.2608 LARSE03R 94+289:14:00:07.055 00402 N 33 30.9287 W 119 33.0648 LARSE03R 94+289:15:00:01.568 00581 N 33 32.5004 W 119 27.6512 LARSE03R 94+289:16:00:17.727 00757 N 33 34.1488 W 119 22.4373 LARSE03R 94+289:17:00:08.771 00923 N 33 35.8234 W 119 17.5013 LARSE03R 94+289:18:00:08.189 01100 N 33 37.2967 W 119 12.0843 LARSE03R 94+289:19:00:09.041 01276 N 33 38.7931 W 119 06.7238 LARSE03R 94+289:20:00:15.892 01460 N 33 40.4540 W 119 01.1934 LARSE03R 94+289:21:00:02.038 01645 N 33 42.1461 W 118 55.6502 LARSE03R 94+289:22:00:03.040 01822 N 33 43.6823 W 118 50.3249 LARSE03R 94+289:23:00:16.347 01991 N 33 45.2109 W 118 45.2325 LARSE03R 94+290:00:00:01.250 02159 N 33 46.7763 W 118 40.1895 LARSE03R 94+290:01:00:03.223 02329 N 33 48.4177 W 118 35.1116 LARSE03R 94+290:02:00:16.623 02491 N 33 49.9201 W 118 30.2992 LARSE03R 94+290:02:37:25.192 02587 N 33 51.0747 W 118 27.8797 LARSE03R 94+290:02:38:46.229 00101 N 33 51.1466 W 118 27.9502 LARSETR2 94+290:03:00:23.054 00152 N 33 52.0566 W 118 29.4076 LARSETR2 94+290:04:00:19.519 00319 N 33 54.8050 W 118 33.7771 LARSETR2 94+290:04:59:09.433 00494 N 33 59.1441 W 118 35.3047 LARSETR2 94-290:05:17:27.928 00101 N 34 00.5065 W 118 35.3833 LARSE02 94+290:06:00:17.404 00129 N 33 58.5106 W 118 35.1231 LARSE02 94+290:07:00:14.853 00292 N 33 54.2299 W 118 35.8275 LARSE02 94+290:08:00:03.996 00442 N 33 50.2701 W 118 36.4737 LARSE02 94+290:09:00:11.887 00599 N 33 46.0755 W 118 37.1957 LARSE02 94+290:10:00:07.081 00762 N 33 41.7912 W 118 38.1739 LARSE02 94+290:11:00:11.012 00924 N 33 37.5272 W 118 38.8884 LARSE02 94+290:12:00:12.071 01086 N 33 33.2521 W 118 39.5734 LARSE02 94+290:13:00:19.431 01243 N 33 29.0833 W 118 40.2080 LARSE02 94+290:14:00:21.256 01397 N 33 25.0075 W 118 40.2710 LARSE02 94+290:15:00:24.276 01543 N 33 21.1104 W 118 40.4225 LARSE02 94+290:16:00:10.167 01692 N 33 17.0818 W 118 40.3679 LARSE02 94+290:17:00:10.257 01842 N 33 13.1128 W 118 40.5788 LARSE02 94+290:18:00:20.462 01978 N 33 09.5246 W 118 40.5967 LARSE02 94+290:19:00:19.537 02112 N 33 05.9164 W 118 40.6276 LARSE02 94+290:20:00:04.363 02261 N 33 01.8875 W 118 40.6963 LARSE02 94+290:21:00:22.191 02408 N 32 58.0202 W 118 41.1395 LARSE02 94+290:22:00:04.289 02556 N 32 54.0071 W 118 41.6480 LARSE02 94+290:23:00:08.091 02723 N 32 49.5139 W 118 42.1385 LARSE02 94+291:00:00:16.082 02898 N 32 44.8263 W 118 42.5964 LARSE02 94+291:01:00:03.382 03077 N 32 40.0689 W 118 43.1260 LARSE02 94+291:01:54:01.400 03215 N 32 38.3049 W 118 43.3906 LARSE02 94+291:01:54:58.840 00101 N 32 38.3632 W 118 43.3877 LARSE02R 94+291:02:00:58.973 00105 N 32 38.7186 W 118 43.2985 LARSE02R 94+291:03:00:59.366 00145 N 32 42.5931 W 118 43.0442 LARSE02R 94+291:03:59:30.434 00184 N 32 46.6377 W 118 42.4137 LARSE02R 94+291:04:59:31.872 00224 N 32 50.6815 W 118 41.9928 LARSE02R 94+291:05:59:32.775 00264 N 32 54.9600 W 118 41.5864 LARSE02R 94+291:06:59:33.541 00304 N 32 59.4535 W 118 40.9761 LARSE02R 94+291:07:59:36.050 00344 N 33 03.6547 W 118 40.7081 LARSE02R 94+291:08:59:37.022 00384 N 33 08.4115 W 118 40.7063 LARSE02R 94+291:09:59:40.175 00424 N 33 13.0746 W 118 40.6950 LARSE02R 94+291:10:59:40.410 00464 N 33 17.7123 W 118 40.4246 LARSE02R 94+291:11:59:41.015 00504 N 33 22.3501 W 118 40.3197 LARSE02R 94+291:12:59:41.279 00544 N 33 27.2905 W 118 40.2475 LARSE02R 94+291:13:59:43.062 00584 N 33 32.1174 W 118 39.8743 LARSE02R 94+291:14:59:44.269 00624 N 33 36.7405 W 118 38.9881 LARSE02R 94+291:15:59:46.210 00664 N 33 41.1264 W 118 38.0487 LARSE02R 94+291:16:59:47.300 00704 N 33 45.6855 W 118 37.5693 LARSE02R 94+291:17:59:48.515 00744 N 33 50.2230 W 118 36.7155 LARSE02R 94+291:18:59:50.415 00784 N 33 54.8195 W 118 35.7287 LARSE02R 94+291:19:56:51.976 00822 N 33 59.1866 W 118 35.0395 LARSE02R 94+291:19:56:51.976 00822 N 33 59.1866 W 118 35.0395 LARSE02R 94-291:20:52:55.502 00101 N 33 58.9955 W 118 34.9105 LARSE02X 94-291:21:00:15.675 00123 N 33 58.4382 W 118 34.9741 LARSE02X 94+291:22:00:03.602 00275 N 33 54.1497 W 118 35.7090 LARSE02X 94+291:23:00:07.734 00455 N 33 49.5534 W 118 36.5912 LARSE02X 94+292:00:00:08.587 00635 N 33 44.7232 W 118 37.6345 LARSE02X 94+292:01:00:12.467 00815 N 33 40.0411 W 118 38.3838 LARSE02X 94+292:02:00:16.561 00995 N 33 35.5514 W 118 39.0806 LARSE02X 94+292:03:00:16.490 01175 N 33 31.0242 W 118 39.8653 LARSE02X 94+292:04:00:18.522 01355 N 33 26.3980 W 118 40.2904 LARSE02X 94+292:04:04:58.929 01369 N 33 26.0795 W 118 40.4389 LARSE02X 94+292:04:05:21.494 00101 N 33 26.0601 W 118 40.4650 LARSE02Y 94+292:05:00:02.389 00265 N 33 27.1016 W 118 40.4038 LARSE02Y 94+292:06:00:06.067 00445 N 33 31.2086 W 118 39.9953 LARSE02Y 94+292:07:00:06.608 00625 N 33 35.5913 W 118 39.2658 LARSE02Y 94+292:08:00:10.380 00805 N 33 39.8117 W 118 38.4313 LARSE02Y 94+292:09:00:15.273 00985 N 33 43.9213 W 118 37.7421 LARSE02Y 94+292:10:00:15.065 01165 N 33 48.0791 W 118 36.9137 LARSE02Y 94+292:11:00:17.304 01345 N 33 52.4458 W 118 36.0768 LARSE02Y 94+292:12:00:00.702 01524 N 33 56.7512 W 118 35.5050 LARSE02Y 94+292:12:31:41.399 01619 N 33 59.0900 W 118 35.1297 LARSE02Y 94-292:13:29:27.255 00101 N 33 59.2088 W 118 34.9838 LARSE02Z 94+292:14:00:06.400 00193 N 33 57.2305 W 118 35.3422 LARSE02Z 94+292:15:00:08.704 00373 N 33 53.2898 W 118 36.1026 LARSE02Z 94+292:16:00:10.146 00553 N 33 48.8349 W 118 36.7070 LARSE02Z 94+292:17:00:12.928 00733 N 33 44.6393 W 118 37.4671 LARSE02Z 94+292:17:50:16.318 00883 N 33 41.1206 W 118 37.7817 LARSE02Z 94+292:17:51:16.279 00101 N 33 41.0819 W 118 37.7084 LARSETR3 94+292:19:00:17.389 00308 N 33 38.2294 W 118 32.7562 LARSETR3 94+292:20:00:01.172 00487 N 33 35.5438 W 118 28.4572 LARSETR3 94+292:21:00:02.924 00667 N 33 32.9193 W 118 23.7531 LARSETR3 94+292:22:00:05.387 00847 N 33 30.4232 W 118 19.0269 LARSETR3 94+292:23:00:09.728 01027 N 33 27.8195 W 118 14.6585 LARSETR3 94-292:23:49:10.440 01174 N 33 25.4579 W 118 11.8203 LARSETR3 94-292:23:51:10.581 00101 N 33 25.3143 W 118 11.8581 LARSE01A 94+293:00:00:09.301 00128 N 33 24.6750 W 118 12.0683 LARSE01A 94+293:01:00:10.601 00308 N 33 20.3659 W 118 13.7052 LARSE01A 94+293:02:00:14.052 00488 N 33 16.0679 W 118 15.3151 LARSE01A 94+293:03:00:15.753 00668 N 33 11.9929 W 118 17.5168 LARSE01A 94+293:04:00:18.514 00848 N 33 07.9846 W 118 19.7611 LARSE01A 94+293:05:00:02.909 01027 N 33 04.0656 W 118 21.5309 LARSE01A 94+293:06:00:03.221 01207 N 33 00.2975 W 118 23.2942 LARSE01A 94+293:06:40:04.022 01327 N 32 58.7739 W 118 23.7394 LARSE01A 94+293:06:40:41.713 00101 N 32 58.8149 W 118 23.7586 LARSE01B 94+293:07:00:01.153 00159 N 33 00.1870 W 118 23.5451 LARSE01B 94+293:08:00:03.507 00339 N 33 04.2791 W 118 21.4781 LARSE01B 94+293:09:00:05.874 00519 N 33 07.9989 W 118 19.4876 LARSE01B 94+293:10:00:08.149 00699 N 33 11.7962 W 118 17.6380 LARSE01B 94+293:11:00:11.048 00879 N 33 15.8636 W 118 15.6575 LARSE01B 94+293:12:00:14.169 01059 N 33 20.2040 W 118 13.6493 LARSE01B 94+293:13:00:15.813 01239 N 33 24.6972 W 118 12.0093 LARSE01B 94+293:13:56:16.171 01407 N 33 28.8957 W 118 10.7140 LARSE01B 94+293:14:00:13.799 00101 N 33 29.1561 W 118 10.8084 LARSE04 94+293:15:00:16.574 00151 N 33 31.1685 W 118 08.3868 LARSE04 94+293:16:00:19.087 00331 N 33 31.9416 W 118 04.5500 LARSE04 94-293:16:44:02.473 00462 N 33 32.5354 W 118 02.3622 LARSE04 94-293:17:12:13.662 00101 N 33 32.8920 W 118 00.6802 MARSE05 94-293:17:18:44.404 00104 N 33 33.0136 W 118 00.1301 lARSE05 94-293:17:45:12.836 00101 N 33 33.4681 W 117 57.7723 test 94-293:18:28:19.082 00101 N 33 32.9983 W 117 55.5490 LARSE05 94+293:18:35:11.795 00111 N 33 32.8422 W 117 56.0770 larse05 Line LARSE06a 94-293:18:35:45.905 00101 N 33 32.8290 W 117 56.1213 LARSE06 94+293:19:00:04.281 00174 N 33 32.2586 W 117 57.9749 LARSE06 94+293:20:00:06.283 00354 N 33 31.3082 W 118 02.7146 LARSE06 94+293:21:00:08.775 00534 N 33 30.2118 W 118 07.4535 LARSE06 94+293:21:28:09.762 00618 N 33 29.7351 W 118 09.6726 LARSE06 Line LARSE06b 94+293:21:47:10.528 00675 N 33 28.6632 W 118 09.3539 LARSE06 94+293:22:00:11.057 00714 N 33 28.4705 W 118 08.2971 LARSE06 94+293:23:00:13.811 00894 N 33 27.9199 W 118 03.3360 LARSE06 94+294:00:00:16.250 01074 N 33 26.9317 W 117 58.3716 LARSE06 94+294:01:00:18.513 01254 N 33 26.1537 W 117 53.4019 LARSE06 94+294:02:00:18.913 01434 N 33 25.2776 W 117 48.5949 LARSE06 94+294:02:31:01.953 01526 N 33 24.8771 W 117 46.0337 LARSE06 Line LARSE06c 94+294:02:42:01.143 01559 N 33 24.2997 W 117 45.3553 LARSE06 94+294:03:00:01.848 01613 N 33 23.0430 W 117 44.6647 LARSE06 94+294:04:00:02.545 01793 N 33 19.0806 W 117 42.6310 LARSE06 94-294:04:31:30.294 01885 N 33 17.0371 W 117 41.4682 LARSE06 APPENDIX 2. DMS-2000 Recording System This Appendix presents notes on DMS-2000 seismic recording system on the R/V Maurice Ewing and the SEG-D data format in which we recorded MCS data on the Ewing. DMS-2000 Recording System The DMS-2000 records demultiplexed seismic data in a standard SEG-D format (SEG Subcommittee on Field Tape Standards, 1994), using a 20-bit (2.5 bytes per sample) recording format. Data logged from peripheral systems (bird controller, gun controller, navigation, etc.) are not written to the SEG-D header blocks, but are rather recorded in a special auxiliary data trace, referred to in the Digicon documentation as SEGD/Trace0 (Rtrace zeroS). The SEG-D General Header (the header that accompanies each shot record), contains the shot number and shot time to the nearest second. For EW94-15, the DMS-2000 was configured to record 180 data channels from 46 four- channel digitizing modules (or "cans"). Only 40 of these cans were actually in use in the streamer, resulting in 160 active channels, numbered 1-160. Channel 1 is the far channel, 160 the near channel. Two channels on-board ship (173 and 174) were used to record the sonobuoy receivers. The remaining channels (161-172, 175-180) are physically on tape, but contain no data. Trace0 consists of a 4051-byte data trace preceding the demultiplexed seismic data, with a channel designation -1. It is flagged by the system as an auxiliary trace. The DMS-2000 also writes a secondary data tape, referred to as the NAVLOG tape. This is recorded in format identical to the SEG-D data tape, but contains only three channels - Trace0 and two data channels. For EW94-15 these were channels 10 and 150, a far-trace and a relative near-trace channel. (Channels to be forked to the NAVLOG tape are selected in the CEO SOL/EOL Auto-Start-End menu of the DMS-2000 system.) SEG-D Format The basic layout of the SEG-D tape is: size in bytes General Header - 96 (three 32-byte blocks) IBG | Trace0 record | 4051 (variable-length sections) IBG | S Data Channel 1 | H RECL*2.5 + 20-byte trace header IBG | O Data Channel 2 | T RECL*2.5 + 20-byte trace header IBG | : : | 1 : : | : Data Channel 184 | RECL*2.5 + 20-byte trace header IBG | EOF - General Header - 96 (three 32-byte blocks) IBG | Trace0 record | S 4051 (variable-length sections) IBG | H Data Channel 1 | O RECL*2.5 + 20-byte trace header : | T : : | : Data Channel 184 | 2 RECL*2.5 + 20-byte trace header IBG | EOF - : : General Header - 96 (three 32-byte blocks) IBG | S Trace0 record | H 4051 (variable-length sections) IBG | O Data Channel 1 | T RECL*2.5 + 20-byte trace header : | : : | N : Data Channel 184 | RECL*2.5 + 20-byte trace header EOF - EOT General Header The General Header consists of three 32-byte blocks, and contains the following relevant fields: byte number data 1-2 FFID 3-4 SEG-D format code (8015 - 20-bit binary demux) 5-6 not used 7-8 shotpoint 9-10 ?? (791) 11 year (94) 12-13 day of year 14 shot hour (GMT) 15 shot minute (GMT) 16 shot second (GMT) These values are recorded in Binary-Coded Decimal (BCD) notation, and are therefore recognizable in a hex dump. The day/hour/minute/second fields above are standard SEG-Y, but the shotpoint location is not defined by the standard. Software that reads SEG-D, such as ProMAX or DISCO, will therefore probably read the shot times, but not the shot points. The location of the shotpoint field must be explicitly defined in the input module. For example, in ProMAX, it is necessary to select "Remap SEGD main header values" in the SEG-D input module, and indicate something like: Input/override main header entries SOURCE,,4B,,,6.5/ where 6.5 indicates the starting location in the header record for the 4-digit BCD value for shotpoint, which is mapped onto the header value SOURCE. The odd value (6.5) for starting location is a peculiarity of ProMAX. ProMAX SEGD input also converts the shot time to absolute seconds stored in a header word TIM_SHOT. You may choose to explicitly identify the time by hour, minute, and second, with an Input/override entry like: SOURCE,,4B,,,6.5/HR_SHOT,GMT SHOT HOUR,2B,,,13.4/MIN_SHOT, GMT SHOT MINUTE,2B,,,14.5/SEC_SHOT,GMT SHOT SECOND,2B,,,15.5/ Trace0 Trace0 contains a wealth of information about the system (e.g., seismic bird information, gun shooting parameters), much of which is also available from other shipboard logging systems. Trace0 data is not accessible from conventional SEGD input software; for access to it, one is advised to use John Diebold's segd_dump program, which reads and reformats to disk various selected portions of Trace0 (Internet address: johnd@lamont.ldgo.columbia.edu). Of course, dumping the Trace0 records from the NAVLOG tapes is much more efficient than reading the data tapes. A note regarding the Trace0 positional information. Navigational data is passed from the navigational computer aboard the Ewing ("Moray") to the DMS-2000 for inclusion in Trace0, where it is stored in Section 11, the "Magnavox Nav Data Block". (Digicon uses Magnavox navigational systems on their vessels). This 211-byte navblock contains latitude and longitude fixes for each shot, which can be read with segd_dump. These positions, however, are "real-time" solutions that have not been adjusted or corrected by the post- processing that is done daily on-board the vessel. The 20-byte individual Demux Trace Headers which precede each data trace have little information of use to the processor, nor does the SEG-D standard suggest that they should. Tape Errors The recurring, persistent 3480 tape drive errors reported on previous Ewing cruises were resolved prior to EW94-15. However, a few SQRT errors did occur, resulting in two shot records being concatenated into one file, with the second record overwriting some portion of the previous one. These files have a variable number of traces, in excess of the normal 180 and were noted in observer logs when possible. The processing flow must be able to read these abnormal files, and pad the channels to create normal ensembles. CEO/CSRU and TAGS Logs The DMS-2000 system also maintains logs and error files of the recording system (CSRU) and the air gun control system (TAGS). The CSRU files are named 'line_id'.rul and 'line_id'.rue for the log and error files, respectively. The corresponding TAGS files are 'line_id'.tal and 'line_id'.tae. All of the information in the TAGS error file is repeated in the TAGS log file, and the CSRU error and log files are complementary. These files are written to DOS floppy disks with the CEO File Handler. Precise Shot Timing And Location Processed GPS shot locations and shot-times (precise to 1 ms from the GPS receiver) are available in a separate file, but are not contained in the SEG-D records. APPENDIX 3. EWING Multichannel Seismic Reflection Tape Log Notes: 160 Channels, 16 Sec Record, 2 ms Sample Rate 180 channels where written to tape but only 160 channels are MCS. Sonobuoy channels: 173,174 3480 CARTRIDGE to 8MM EXABYTE TAPE TRANSFER Line LARSE 01 was an OBS line without MCS recording Start Line LARSE 01R Exabyte Tape: LA01 Line: LARSE 01R JD 287 1156Z 3480 Cartridge No. FFID Range Shot Point Range 1 101-153 104-156 2 154-206 157-209 3 207-259 210-262 4 260-312 263-315 5 313-365 316-368 Exabyte Tape: LA02 Line: LARSE 01R JD 287 3480 Cartridge No. FFID Range Shot Point Range 6 366-418 369-421 Exabyte Tape: LA03 Line: LARSE 01R 3480 Cartridge No. FFID Range Shot Point Range 7 419-471 422-474 8 472-524 475-527 9 525-577 528-580 10 578-630 581-633 11 631-683 634-686 Exabyte Tape: LA04 Line: LARSE 01R 3480 Cartridge No. FFID Range Shot Point Range 12 684-736 687-739 13 737-789 740-792 14 790-842 793-845 15 843-895* 846-898* 16 896-948 899-951 *3480 Cartridge No. 15: Write Error, FFID 891 bad, FFID 892-894 do not exist Exabyte Tape: LA05 Line: LARSE 01R 3480 Cartridge No. FFID Range Shot Point Range 17 949-1001 952-1004 18 1002-1054 1005-1057 19 1055-1103* 1058-1106* *Abnormal termination 3480 Cartridge No. 19 Exabyte Tape: LA06 Line: LARSE 01R 3480 Cartridge No. FFID Range Shot Point Range 19 1104-1107* 1107-1110* 20 1108-1160 1111-1163 21 1161-1213 1164-1217 22 1214-1266 1218-1270 23 1267-1319 1271-1323 24 1320-1372 1324-1376 *Resume with last files of 3480 cartridge No. 19. File 1342 may be bad. Exabyte Tape: LA07 Line: LARSE 01R JD 287 1919-2110Z 3480 Cartridge No. FFID Range Shot Point Range 25 1373-1425 1377-1429 26 1426-1478 1430-1483 27 1479-1531 1483-1535 28 1532-1584 1536-1588 29 1585-1637 1589-1641 30 1638-1690 1642-1694 Exabyte Tape: LA08 Line: LARSE 01R JD 287 2110-2300Z 3480 Cartridge No. FFID Range Shot Point Range 31 1691-1743 1695-1747 32 1744-1796 1748-1800 33 1797-1849 1801-1853 34 1850-1902 1854-1906 35 1903-1955 1907-1959 36 1956-2008 1960-2012 Files 1810, 1827 may be bad Exabyte Tape: LA09 Line: LARSE 01R JD 287-288 2301Z-? 3480 Cartridge No. FFID Range Shot Point Range 37 2009-2061 2013-2065 38 2062-2114 2066-2118 39 2115-2126 2119-2130 40 2127-2178 2131-2182 41 2179-2231 2183-2235 42 2232-2284 2236-2288 FFID 2129, 2130, 2131 may be bad. Exabyte Tape: LA10 Line: LARSE 01R JD 288 0036Z-? 3480 Cartridge No. FFID Range Shot Point Range 43 2285-2337* 2289-2341* 44 2338-2390 2342-2394 45 2391-2404 2395-2408 *End of line (EOL) LARSE01R FFID 2307, 288/0044z Begin Line LARSE 01X Exabyte Tape: LA11 Line: LARSE 01X JD 288 0135-0330Z 3480 Cartridge No. FFID Range Shot Point Range 45A 101-153 102-155 46 154-206 156-208 47 207-259 209-261 48 260-312 262-314 49 313-365 315-367 50 366-418 368-420 Shot 115 missed. Exabyte Tape: LA12 Line: LARSE 01X JD 288 0330-0519Z 3480 Cartridge No. FFID Range Shot Point Range 51 419-471 421-473 52 472-524 474-526 53 525-577 527-579 54 578-630 580-632 55 631-683 633-685 56 684-736 686-738 Exabyte Tape: LA13 Line: LARSE 01X JD 288 0519-0630Z 3480 Cartridge No. FFID Range Shot Point Range 57 737-789 739-791 58 790-842 792-845 59 843-895 846-898 60 896-927* 899-930 *End of Line: LARSE 01X FFID 927, 288/0630z Start of Line: LARSE 01Y FFID 101 288/0630z Exabyte Tape: LA14 Line: LARSE 01Y JD 288 0640-0844Z 3480 Cartridge No. FFID Range Shot Point Range 61 101-153 116-168 62 154-206 169-221 63 207-259 222-274 64 260-312 275-327 65 313-365 328-380 66 366-418 381-433 Exabyte Tape: LA15 Line: LARSE 01Y JD 288 0844-1037Z 3480 Cartridge No. FFID Range Shot Point Range 67 419-471 434-486 68 472-524 487-539 69 525-577 540-592 70 578-630 593-645 71 631-683 646-698 72 684-736 699-751 Exabyte Tape: LA16 Line: LARSE 01Y JD 188 1038Z-? 3480 Cartridge No. FFID Range Shot Point Range 73 737-789 752-804 74 790-842 805-857 75 843-895 858-910 76 896-948 911-963 77 949-1001 964-1016 78 1002-1044 1017-1059 END OF LINE LARSE 01Y FFID=1009 TIME=1212z JD288 TURN FFID= 110-1044 1227z JD288 START OF LINE LARSE TR1 FFID=101 TIME=1227z JD288 Exabyte Tape: LA17 3480 Cartridge No. FFID Range Shot Point Range 79 101-153 103-156 80 No Tape No Tape 81 155-206 158-209 82 207-259 210-262 83 260-312 263-336 84 313-365 337-389 Tape popped out at end of line with no data on it -- Does not exist 3480 Cartridge No. FFID Range Shot Point Range 85 No Tape No Tape INTERRUPTION OF LARSE TR1 FFID=367 TIME=1428z JD288 Streamer ballast problems due to kelp on tail buoy. Problem fixed and near-offset part of streamer weighted. RESUMPTION OF LARSE TR1 FFID= 101 TIME=1748z JD288 Exabyte Tape: LA18 3480 Cartridge No. FFID Range Shot Point Range 86 101-153 103-155 87 155-206 157-208 88 207-259 209-261 89 260-312 262-314 90 313-365 315-367 91 366-418 368-420 Exabyte Tape: LA19 3480 Cartridge No. FFID Range Shot Point Range 92 419-471 421-473 93 472-524 474-526 94 525-577 527-579 95 578-630 580-632 96 631-683 633-685 97 684-736 686-738 98 737-755 739-757 END OF LINE LARSE TR1 FFID=716 TIME=2119z JD288 START OF LINE LARSE 03 FFID=101 TIME=2146z JD288 Exabyte Tape: LA20 JD 288 2146-2240Z 3480 Cartridge No. FFID Range Shot Point Range 99 101-153 102-154 100 154-206 155-207 101 207-251 208-252 Abnormal termination 3480 Reel 101 FFID 251, retry unsuccessful, 9 shots not copied. File 244 may be bad. Exabyte Tape: LA21 JD 288 2241-2339Z 3480 Cartridge No. FFID Range Shot Point Range 102 260-312 261-313 103 313-365 314-366 104 366-418 367-419 File 329 may be bad. Exabyte Tape: LA22 JD 288-289 2340-0035Z 3480 Cartridge No. FFID Range Shot Point Range 105 419-471 420-472 106 472-524 473-525 107 525-577 526-578 Bad file 442 skipped. Exabyte Tape: LA23 JD 289 0035-0227Z 3480 Cartridge No. FFID Range Shot Point Range 108 578-630 579-631 109 631-683 632-684 110 684-736 685-737 111 737-789 738-790 112 790-842 791-843 113 843-895 844-896 File 797 may be bad. Exabyte Tape: LA24 JD 289 0227-0419Z 3480 Cartridge No. FFID Range Shot Point Range 114 896-948 897-949 115 949-1001 950-1002 116 1002-1054 1003-1055 117 1055-1107 1056-1108 118 1108-1160 1109-1187 119 1161-1213 1188-1241 Exabyte Tape: LA25 JD 289 0419-0607Z 3480 Cartridge No. FFID Range Shot Point Range 120 1214-1266 1242-1294 121 1267-1319 1295-1347 122 1320-1372 1348-1400 123 1373-1425 1401-1453 124 1426-1478 1454-1506 Exabyte Tape: LA25A JD 289 0550-0607Z 3480 Cartridge No. FFID Range Shot Point Range 12r 1479-1508 1507-1536 FFID 1508 traces 1-137 (should be 1-180); FFID 1509 traces 1-1 (bad record). FFID 1508-1509 skipped - bad. Abnormal termination tape 125. FFID 1509 lost; files 1510-1531 not copied to tape Exabyte Tape: LA26 JD 289 0608-0801Z start record of channels 1-160 only 3480 Cartridge No. FFID Range Shot Point Range 126 1532-1584 1560-1612 127 1585-1637 1613-1665 128 1638-1690 1666-1718 129 1691-1743 1719-1771 130 1744-1796 1772-1824 131 1797-1849 1825-1877 Exabyte Tape: LA27 JD 289 0802-0959Z 3480 Cartridge No. FFID Range Shot Point Range 132 1850-1902 1878-1930 133 1903-1955 1931-1983 134 1956-2008 1984-2036 135 2009-2061 2037-2093 136 2062-2114 2094-2146 137 2115-2167 2147-2199 Exabyte Tape: LA28 JD 289 1000-1155Z 3480 Cartridge No. FFID Range Shot Point Range 138 2168-2220 2200-2252 139 2221-2273 2253-2305 140 2274-2326 2306-2359 141 2327-2379 2360-2412 142 2380-2432 2413-2465 143 2433-2479 2466-2512 End of Line LARSE 03 on 3480 Reel 143, FFID 2479, 289/1155 Start of Line LARSE 03R Exabyte Tape: LA29 JD 289 1212-1424Z 3480 Cartridge No. FFID Range Shot Point Range 144 101-153 102-154 145 154-206 155-207 146 207-259 208-260 147 260-312 261-313 148 313-365 314-366 149 366-418 367-419 150 419-471 420-472 FFID 348-365 were not transcribed from 3480 Cartridge No. 148 because of read error. Exabyte Tape LA29A JD 289 will contain FFID 348-365 if possible to read. Exabyte Tape: LA30 JD 289 1424-1631Z 3480 Cartridge No. FFID Range Shot Point Range 151 472-524 473-525 152 525-577 526-528 153 578-630 579-631 154 631-683 632-684 155 684-736 685-737 156 737-789 738-790 157 790-842 791-843 Exabyte Tape: LA31 JD 289 1632-1840Z 3480 Cartridge No. FFID Range Shot Point Range 158 843-895 844-896 159 896-948 897-949 162 951-1002 952-1003 163 1003-1055 1004-1056 164 1056-1108 1057-1109 165 1109-1161 1110-1162 166 1162-1214 1163-1215 3480 Cartridge Nos. 160 and 161 do not exist. Files 949-951 lost. SP 950-951 lost. 3480 Cartridge No. 162 starts with file 952. Cartridge did not get changed. Exabyte Tape: LA32 JD 289 1840-2024Z 3480 Cartridge No. FFID Range Shot Point Range 167 1215-1267 1216-1268 168 1268-1320 1269-1321 169 1321-1373 1322-1374 170 1374-1426 1375-1427 171 1427-1479 1428-1480 172 1480-1528 1481-1529 Start channels 1-180 per FFID. Abnormal termination 3480 Cartridge No. 172 FFID 1528, 3 files lost; shots 1530-1533 lost. Exabyte Tape: LA33 JD 289 2024-2216Z 3480 Cartridge No. FFID Range Shot Point Range 173 1533-1585 1534-1601 174 1586-1638 1602-1655 175 1639-1691 1656-1708 176 1692-1744 1709-1761 177 1745-1797 1762-1814 178 1798-1850 1815-1867 Shots lost because firing interval became too short = 1563, 1565, 1567, 1569, 1571, 1573, 1575, 1577, 1579, 1581, 1583, 1585, 1587, 1589, 1591. Exabyte Tape: LA34 JD 289-290 2216-0009Z. File 2036 may be bad. 3480 Cartridge No. FFID Range Shot Point Range 179 1851-1903 1868-1920 180 1904-1956 1921-1973 181 1957-2009 1974-2026 182 2010-2062 2027-2079 183 2063-2115 2080-2132 184 2116-2168 2133-2185 Exabyte Tape: LA35 JD 290 0010-0144Z 3480 Cartridge No. FFID Range Shot Point Range 185 2169-2221 2186-2238 186 2222-2274 2239-2291 187 2275-2327 2292-2344 188 2328-2380 2345-2397 189 2381-2433 2398-2450 Sonobouy #2 on 3480 Cartridge Nos. 186,187,188,189,190 Exabyte Tape: LA36 JD 290 0144-0229Z 3480 Cartridge No. FFID Range Shot Point Range 190 2434-2486 2451-2503 191 2487-2539 2504-2556 192 2540-2551 2557-2568 End of Line LARSE 03R at FFID 2551 Start of Line LARSE TR2 Exabyte Tape: LA37 3480 Cartridge No. FFID Range Shot Point Range 193 101-153 102-154 194 154-206 155-207 195 207-259 208-260 196 260-274 261-275 Exabyte Tape: LA38 3480 Cartridge No. FFID Range Shot Point Range 197 101-153 299-351 198 154-206 352-404 199 207-259 405-457 200 260-295 458-493 End of Line LARSE TR2 Beginning of Line LARSE 02 (outbound leg) Streamer straight at shot 167 Exabyte Tape: LA39 JD290 0551-0751z 3480 Cartridge No. FFID Range Shot Point Range 201 102-153 105-156 203 155-206 158-209 204 207-259 210-262 205 260-312 263-315 206 313-365 316-368 207 366-418 369-421 **No 3408 Cartridge No. 202; FFID 157, 158, 187, 188 are bad. Exabyte Tape: LA40 JD290 0752-0932z 3480 Cartridge No. FFID Range Shot Point Range 208 419-471 422-474 209 472-524 475-527 210 525-577 528-580 211 578-630 581-633 212 631-683 634-686 213 684-736 687-739 Exabyte Tape: LA41 JD290 0932-1149z 3480 Cartridge No. FFID Range Shot Point Range 214 737-789 740-792 215 790-842 793-845 Exabyte Tape: LA41A 3480 Cartridge No. FFID Range Shot Point Range 216 843-895 846-898 217 896-948 899-951 218 949-1001 952-1004 219 1002-1054 1005-1057 File 876 skipped - bad Exabyte Tape: LA42 JD290 1149-1351z 3480 Cartridge No. FFID Range Shot Point Range 220 1055-1107 1058-1111 221 1108-1160 1112-1164 222 1161-1213 1165-1217 223 1214-1266 1218-1270 224 1267-1319 1271-1323 225 1320-1372 1324-1376 FFID 1063 may be bad Exabyte Tape: LA43 JD290 1351-1600z 3480 Cartridge No. FFID Range Shot Point Range 226 1373-1425 1377-1429 227 1426-1478 1430-1482 228 1479-1531 1483-1535 229 1532-1584 1536-1588 230 1585-1637 1589-1641 231 1638-1690 1642-1694 Exabyte Tape: LA44 JD290 1601-1815z 3480 Cartridge No. FFID Range Shot Point Range 232 1691-1743 1695-1747 233 1744-1796 1748-1801 234 1797-1849 1802-1854 235 1850-1902 1855-1907 236 1903-1955 1908-1960 237 1956-2008 1961-2013 Shot 1787 not recorded Exabyte Tape: LA45 JD290 1816-2028z 3480 Cartridge No. FFID Range Shot Point Range 238 2009-2061 2014-2066 239 2062-2114 2067-2119 240 2115-2167 2120-2172 241 2168-2220 2173-2225 242 2221-2273 2226-2278 243 2274-2326 2279-2331 Exabyte Tape: LA46 JD290 2029-2234z 3480 Cartridge No. FFID Range Shot Point Range 244 2327-2379 2332-2384 245 2380-2432 2385-2437 246 2433-2485 2438-2490 247 2486-2538 2491-2543 248 2539-2591 2544-2596 249 2592-2644 2597-2649 Exabyte Tape: LA47 JD290-291 2234-0023 3480 Cartridge No. FFID Range Shot Point Range 250 2645-2697 2650-2702 251 2698-2750 2703-2755 252 2751-2803 2756-2808 253 2804-2856 2809-2961 254 2857-2909 2862-2914 255 2910-2962 2915-2967 FFID 2919 may be bad Exabyte Tape: LA48 JD291 0023-0147 3480 Cartridge No. FFID Range Shot Point Range 256 2963-3015 2968-3020 257 3016-3068 3021-3073 258 3069-3121 3074-3126 259 3122-3174 3127-3179 260 3175-3197 3180-3202 Start turn at FFID 3095, 0108z, shotpoints 3023,3024,3026,3027 had errors Start of Line LARSE 02R Shot Interval = 90 secs (Not a useful MCS Pass) Exabyte Tape: LA49 JD291 0148-0952z 3480 Cartridge No. FFID Range Shot Point Range 261 101-153 102-154 262 154-206 155-207 263 207-259 208-260 264 260-312 261-313 265 313-365 314-366 266 366-418 367-419 267 419-471 420-472 Exabyte Tape: LA50 JD291 0953-1955z 3480 Cartridge No. FFID Range Shot Point Range 268 472-524 473-525 269 525-577 526-578 270 578-630 579-631 271 631-683 632-684 272 684-736 685-737 273 737-789 738-790 274 790-821 791-822 End of Line 02R FFID 821, 291/1955 Start Line LARSE 02X Exabyte Tape: LA51 J.D. 291 2103z-2249z 3480 Cartridge No. FFID Range Shot Point Range 275 101-153 104-156 276 154-206 157-209 277 207-259 210-262 278 260-312 263-315 279 313-365 316-368 280 366-418 369-421 Exabyte Tape: LA52 J.D. 291-292 2249z-0035z 3480 Cartridge No. FFID Range Shot Point Range 281 419-471 422-474 282 472-524 475-527 283 525-577 528-580 284 578-630 581-633 285 631-664 634-667 286 684-736 688-740 I/O error 3480 Cartridge No. 285, FFID 665-683 not copied, SP 678 lost. Is 3480 Cartridge No. 286 here? Exabyte Tape: LA52A not yet copied 0000z-0017z 3480 Cartridge No. FFID Range Shot Point Range 285 631-683 634-688 Error at file 664; not able to read beyond yet; FFID 664-683 missing on 8mm. Exabyte Tape: LA53 J.D. 292 0035z-0203z 3480 Cartridge No. FFID Range Shot Point Range 287 737-789 741-793 288 790-842 794-846 289 843-895 847-899 290 896-948 900-952 291 949-978 953-982 I/O error, last good file=978 3480 Cartridge No. 291; unable to read beyond FFID 978. Exabyte Tape: LA53A J.D. 292 0204z-0221z 3480 Cartridge No. FFID Range Shot Point Range 292 1002-1054 1006-1058 Exabyte Tape: LA53B not yet copied 0146z-0203z 3480 Cartridge No. FFID Range Shot Point Range 291 949-1001 953-1005 Error at FFID 978/979; unable to read beyond yet; FFID 979-1001 still not on 8mm. Exabyte Tape: LA54 J.D. 292 0222z-0359z 3480 Cartridge No. FFID Range Shot Point Range 293 1055-1107 1059-1111 294 1108-1160 1112-1164 295 1161-1189 1165-1195 296 1190-1241 1196-1247 297 1242-1294 1248-1300 298 1295-1345 1301-1351 End of Line LARSE 02X Beginning of Line LARSE 02Y Exabyte Tape: LA55 3480 Cartridge No. FFID Range Shot Point Range 299 101-153 102-154 301 155-206 156-207 302 207-259 208-260 303 260-312 261-313 304 313-365 314-366 305 366-418 367-419 Tape-label error -- No label for 3480 Cartridge No. 300 printed. Exabyte Tape: LA56 3480 Cartridge No. FFID Range Shot Point Range 306 419-471 420-472 307 472-524 473-525 308 525-577 526-578 309 578-630 579-631 310 631-683 632-684 311 684-736 685-737 Exabyte Tape: LA57 3480 Cartridge No. FFID Range Shot Point Range 312 737-789 738-790 313 790-842 791-843 314 843-895 844-896 315 896-948 897-949 316 949-1001 950-1002 317 1002-1054 1003-1055 Exabyte Tape: LA58 3480 Cartridge No. FFID Range Shot Point Range 318 1055-1107 1056-1108 319 1108-1160 1109-1161 320 1161-1213 1162-1214 321 1214-1266 1215-1267 322 1267-1319 1268-1320 323 1320-1372 1321-1373 Exabyte Tape: LA59 3480 Cartridge No. FFID Range Shot Point Range 324 1373-1425 1374-1426 325 1426-1478 1427-1479 326 1479-1531 1480-1533 327 1532-1584 1534-1586 328 1585-1616 1587-1618 END OF LINE LARSE 02Y at SP 1618, File 1616 Start Of Line LARSE 02Z 3480 Reel 329 Exabyte Tape: LA60 3480 Cartridge No. FFID Range Shot Point Range 329 101-153 122-174 330 154-206 175-227 331 207-259 228-280 332 260-312 281-333 333 313-365 334-386 334 366-418 387-439 Exabyte Tape: LA61 3480 Cartridge No. FFID Range Shot Point Range 335 419-471 440-492 336 472-524 493-545 337 525-577 546-598 338 578-630 599-651 339 631-683 652-704 340 684-736 705-757 Exabyte Tape: LA62 3480 Cartridge No. FFID Range Shot Point Range 341 737-789 758-810 342 790-842 811-863 End of Line LARSE 02Z Beginning of Line LARSE TR3 Exabyte Tape: LA63 3480 Cartridge No. FFID Range Shot Point Range 343 844-895 106-157 344 896-948 158-210 345 949-1001 211-263 346 1002-1054 264-316 347 1055-1107 317-369 348 1108-1160 370-422 Exabyte Tape: LA64 3480 Cartridge No. FFID Range Shot Point Range 349 1161-1213 423-475 350 1214-1266 476-528 351 1267-1319 529-581 352 1320-1372 582-634 353 1373-1425 635-687 354 1426-1478 688-740 Exabyte Tape: LA65 3480 Cartridge No. FFID Range Shot Point Range 355 1479-1531 741-793 356 1532-1584 794-846 357 1585-1637 847-899 358 1638-1690 900-925 359 1691-1743 953-1005 360 1744-1796 1006-1058 Exabyte Tape: LA66 J.D. 3480 Cartridge No. FFID Range Shot Point Range 361 1797-1849 1059-1111 362 1850-1873 1112-1135 End Line LARSE TR3 file1873 SP 1135 Start LARSE 01A Exabyte Tape: LA67A J.D. 292-293 2352z-0137z 3480 Cartridge No. FFID Range Shot Point Range 363 101-153 103-155 NO 3480 REEL 364 NO 3480 REEL 364 NO 3480 REEL 364 365 155-206 157-208 366 207-259 209-261 367 260-312 262-314 368 313-365 315-367 369 366-418 368-420 SP 156 lost; FFID 269/270, 302/303 may be bad Exabyte Tape: LA67 J.D. 293 0138z-0323z 3480 Cartridge No. FFID Range Shot Point Range 370 419-471 421-473 371 472-524 474-526 372 525-577 527-579 373 578-630 580-632 374 631-683 633-685 375 684-736 686-738 Exabyte Tape: LA68 J.D. 293 0324z-0434z 3480 Cartridge No. FFID Range Shot Point Range 376 737-789 739-791 377 790-842 792-844 378 843-895 845-897 379 896-948 898-950 Exabyte Tape: LA69 J.D. 293 0434z-0558z 3480 Cartridge No. FFID Range Shot Point Range 380 949-1001 951-1003 381 1002-1054 1004-1056 382 1055-1107 1957-1109 383 1108-1160 1110-1162 384 1161-1199 1163-1201 End of Line LARSE 01A Start of Line LARSE 01B Exabyte Tape: LA70 J.D. 293 0641z-0827z 3480 Cartridge No. FFID Range Shot Point Range 385 101-153 102-154 386 154-206 155-207 387 207-259 208-260 388 260-312 261-313 389 313-365 314-366 390 366-418 367-419 Exabyte Tape: LA71 J.D. 293 0827z-1013z 3480 Cartridge No. FFID Range Shot Point Range 391 419-471 420-472 392 472-524 473-525 393 525-577 526-578 394 578-630 579-631 395 631-683 632-684 396 684-736 685-737 Exabyte Tape: LA72 J.D. 293 1013z-1201z 3480 Cartridge No. FFID Range Shot Point Range 397 737-789 738-797 398 790-842 798-850 399 843-895 851-903 400 896-948 904-956 401 949-1001 957-1009 402 1002-1054 1010-1062 SP 745, 746, 753-757 lost Exabyte Tape: LA73 J.D. 293 1201z-1355z 3480 Cartridge No. FFID Range Shot Point Range 403 1055-1107 1063-1115 404 1109-1160 1117-1168 405 1161-1213 1169-1221 406 1214-1266 1222-1274 407 1267-1319 1275-1327 408 1320-1372 1328-1380 409 1373-1396 1381-1404 SP 1116 lost End of Line LARSE 01B Start of Line LARSE 04 Exabyte Tape: LA74 J.D. 293 1443z-1612z 3480 Cartridge No. FFID Range Shot Point Range 410 101-153 101-153 411 154-206 154-206 412 207-259 207-259 413 260-312 260-312 414 313-365 313-365 415 366-368 366-367 Line terminated because chase boat caught in streamer. Add data to end of LARSE 01B. End of Line LARSE 04 Start of Line LARSE-06 Exabyte Tape: LA75 J.D. 293 1836z-2021z 3480 Cartridge No. FFID Range Shot Point Range 416 101-153 102-154 417 154-206 155-207 418 209-259 210-260 419 260-312 261-313 420 313-365 314-366 421 366-418 367-419 FFID 133 bad, not copied?; files 207, 208 lost. Exabyte Tape: LA76 J.D. 293 2202z-2208z 3480 Cartridge No. FFID Range Shot Point Range 422 419-471 420-472 423 472-524 473-525 424 525-577 526-578 425 578-630 579-631 426 631-683 632-685 427 684-736 686-738 Start turn at JD 293 2128z about FFID 630, end turn at FFID 683, 293/2147 (streamer not straight). SP 606 bad?, SP 637 lost. Exabyte Tape: LA77 J.D. 293 2209z-2354z 3480 Cartridge No. FFID Range Shot Point Range 428 737-789 739-791 429 790-842 792-844 430 843-895 845-897 431 896-948 898-950 432 949-1001 951-1003 433 1002-1054 1004-1056 Exabyte Tape: LA78 J.D. 293-294 2354z-0140z 3480 Cartridge No. FFID Range Shot Point Range 434 1055-1107 1057-1110 435 1108-1160 1111-1163 436 1161-1213 1164-1216 437 1214-1266 1217-1269 438 1268-1319 1271-1322 439 1320-1372 1323-1375 SP 1065 lost; file 1267 lost; SP 1278 bad? Exabyte Tape: LA79 J.D. 294 0141z-0327z 3480 Cartridge No. FFID Range Shot Point Range 440 1373-1425 1376-1428 441 1426-1478 1429-1481 442 1479-1531 1482-1534 443 1532-1584 1535-1587 444 1585-1637 1588-1640 445 1638-1690 1641-1693 Exabyte Tape: LA80 J.D. 294 0327z-0430z 3480 Cartridge No. FFID Range Shot Point Range 446 1691-1743 1694-1746 447 1744-1796 1747-1799 448 1797-1814 1800-1819 449 1816-1866 1821-1871 450 1867-1878 1872-1883 No FFID 1815 End of Line LARSE -06 End of Ewing Cruise APPENDIX 4. DATA REDUCTION CRUISE SUMMARY EW-9415 LARSE Experiment: Seismic Survey offshore Los Angeles/Northridge Long Beach, CA - San Diego, CA , U.S.A. 10/03/94 (JD-286) -- 10/10/94 (JD-294) CHIEF SCIENTISTS: Thomas Brocher, USGS (brocher@andreas.wr.usgs.gov) SCIENCE OFFICER: Bruce A. Francis (baf@ldeo.columbia.edu) DATA REDUCTION: Stefanus Budhypramono (dared@ldeo.columbia.edu) R/V MAURICE EWING SCIENCE OVERVIEW: This project involved onshore-offshore seismic profiling of the crustal structure in the greater Los Angeles area, to identify and better understand the earthquake hazards of the region. The Ewing served as a source of seismic energy for both multichannel seismic reflection profiling as well as for an dense array of land stations. Three main lines were run: one through the Sierra Madre epicenter and Los Angeles Basin, one through the epicenter of the Northridge earthquake, and a third trending NE-SW through the Los Angeles basin. TRUE TIME CLOCK: Instrument: Kinemetric/TrueTime Division Model GPS-DC GPS Synchronized Clock Logging: 1 minute intervals NOTE: The True Time clock is used to adjust the CPU clock of the logging computer. The logging computer captures the continuous time records from the clock and provides these as a service to the rest of the network via a UDP broadcast. This enables the computers on the network to adjust their CPU times to UTC time. DAY TIME COMMENTS 286 1530 start of cruise, started logging/processing 294 1600 end of cruise; stopped logging/processing SPEED AND HEADING: Instrument: Furuno CI-30 2-axis Doppler speed log, Sperry MK-27 gyro Logging: 3 second intervals Checking: visual check of plot of data Smoothing: mean value of all good values within the same minute DAY TIME COMMENTS 286 1530 start of cruise; started logging/processing 294 1600 end of cruise ; stopped logging/processing TRANSIT SATELLITE FIXES: Instrument: Magnavox MX-1107RS dual frequency Transit satellite receiver Logging: all fixes Checking: reject receiver flagged fixes, fixes with high drifts in navigation DAY TIME COMMENTS 286 1530 start of cruise; started logging/processing 294 1600 end of cruise ; stopped logging/processing GPS SATELLITE FIXES: Instrument: Magnavox MX-4200 Global Positioning System receiver Logging: 10 second intervals on GPS MX-4200 #1 10 second intervals on GPS MX-4200 #2 Checking: minimum number of SATs: 3 dilution of precision maximum: north = 4.0, east = 4.0 carrier signal-noise ratio minimum: 35.0 standard deviation maximum: north =4.0, east = 4.0 time step maximum: 3 speed maximum: 30.0 compared GPS speed and course with Furuno smooth speed and heading compared positions with Transit-Furuno navigation reject fixes with high drifts in navigation reject fixes producing Eotvos correction errors in gravity larger than 5 mGals Interpolation: interpolated positions at 00, 30 seconds of each minute Smoothing: smoothed interpolated positions with 9 or 41 point running average depending on the quality of GPS data and the sea state. Note: The GPS data has a sinusoidal wave which is assumed to come from some degrading of the GPS quality for civilian usage. This wave seems to vary in period and shapes and is not a perfect sine curve. The periods are less than 20 minutes. The amplitu des tend to vary over 24 hours and the sea state condition. This degrading produces a false ship's track in real-time navigation and introduces extreme errors, up to 10 mGals, in the Eotvos correction for the gravity. As this problem varies in its intensit y depending on the sea state and GPS data quality itself, several methods of data reduction has been developed to achieve the best possible navigation. 1. A 9 point (4 minutes) GPS smoothing 2. A 9 point (4 minutes) GPS smoothing, decimated to a 20 min. fixes 3. A 41 point (20 minutes) GPS smoothing 4. A 41 point (20 minutes) GPS smoothing, decimated to a 20 min. fixes It should be noted that the use of 41 point smoothing causes the turn to "widens". Hence, in the instances where a 41 point smoothing is called for, the GPS data at and around the turn are decimated to 20 minutes. Throughout this cruise, a 9 point (4 minutes) GPS smoothing, decimated to a 20 min. fixes were used to produce final navigation data. DAY TIME COMMENTS 286 1530 started data logging/processing 294 1600 end of cruise ; stopped data logging/processing NAVIGATION: A "1 minute navigation" is produced from the above sources, which in this cruise is a 9 point (4 minutes) GPS smoothing, decimated to a 20 min. fixes. Acceptable fixes are merged at 1 per minute with priority given to GPS. The smooth speed and heading dat a is used to fill any gaps of 2 minutes or longer between fixes by computing 1 minute DR'ed positions corrected for set and drift between fixes. The DR'ed positions are produced at 00 seconds of each minute. Chief scientist's final data: 1 minute navigation. FORMAT: n.ddd yy+ddd:hh:mm:ss.mmm N 12 12.1234 E 123 12.1234 id 123.1 12.1 yr. day time lat. lon id set drift Lamont database: 1 minute navigation, in MGG format. DAY TIME COMMENTS 286 1530 started data processing 294 1600 end of cruise ; stopped data processing SEA TEMPERATURE: Instrument: Omega DP10 Series Logging: 1 minute intervals Checking: none Smoothing: none Chief scientist's final data: one minute data, merged with navigation. Lamont database: one minute data, merged with navigation. FORMAT: ct.nddd yy+ddd:hh:mm:ss:mmm N 12 12.1234 E 123.1234 26.3 yr day time lat lon sea_temp (in oC) DAY TIME COMMENTS 286 1530 started data processing 294 1600 end of cruise ; stopped data processing MAGNETIC: Instrument: Varian V75 magnetometer Logging: 6 second intervals Checking: visual check of plot of data Reference field: International Geomagnetic Reference Field 1990 (IGRF 1990 ) model of the main field at 1985.0 and a predictive model of the secular variation for adjusting to dates between 1990.0 and 1995.0. Residual field: Applied by bi-linear interpolation across a 1 degree square. Chief Scientist's final data: final calibrated and cleaned data. FORMAT: mg.nddd yr+ddd:hh:mm:ss.mmm N 12 12.1234 E 123 12.1234 41200.8 -367.1 yr. day time lat lon total_intensity anomaly Lamont Database: interpolated total intensity value at 00 second of each minute NOTE: DAY TIME COMMENTS 286 2000 started logging 291 1624-2359 maggie off the water; no data 292 0000-0533 maggie off the water; no data 292 1710-2003 bad maggie data ; data removed 294 0440 maggie off the water; end of logging ADCP (Acoustic Doppler Current Profilers): Instrument: RD Instrument RD-VM Model ADCP Logging: logging is done by a 386 IBM PC compatible Checking: none Smoothing: none Chief scientist's final data: processed data file format and navigation data file format. Lamont database: processed data file format and navigation data file format. FORMAT: Refer to Transect User's Manual for Narrowband ADCP Appendix B. DAY TIME COMMENTS 286 1530 beginning of the cruise ; started logging/processing 294 1600 end of cruise; stopped logging/processing BATHYMETRY: Instrument: Krupp Atlas Hydrosweep Center Beam Logging: At each ping of Hydrosweep, data is being broadcasted real time to the network, which is received by data logger. The logger computer then extracted the center beam depth. Checking: Visual checking aided by graphic editor to remove major spikes. Chief scientist's final data: final calibrated and cleaned center beam data, two nearest point to the minute interpolated to even minute. Merged with final navigation. Depth is in meters. FORMAT: hb.nddd yy+ddd:hh:mm:ss:mmm N 12 12.1234 E 123 12.1234 2222.0 yr. day time lat. lon depth_in_meters Lamont database: final calibrated and cleaned data, interpolated to even minute. Merged with final navigation. MGG format. Depth is in fathoms. NOTE: At the beginning of EW-9414, a problem was found with the swath data coming out of the Hydrosweep to the logging computer "olive". An "Unknown data type" error message appeared in "get_hs" log file. Upon closer inspection, this message was generated because the data coming out of the serial line seems to be mangled if it happens to coincide with the pop of the seismic guns. It has yet to be determined whether this was caused by the shock of the guns, or it was an acoustic-interference problem. DAY TIME COMMENTS 286 1520 started logging/processing 291 0104-0542 Hydrosweep was shut off to trace missing data problem 291 0837-0856 Hydrosweep was shut off to trace missing data problem 294 1600 end of cruise; stopped logging/processing SHOT TIME & GUN DEPTH: IInstrument: L-DEO Time Tagger and GunDepth Interface Logging: Shot Time from the Time tagger. Gun Depth from Gun Depth Interface FORMAT: ts.nddd (shot time) 94+173:00:04:04.333 000172 N 40 56.5884 W 125 42.6913 mcs-6a SHOT TIME shotnum lat lon line name FORMAT: dg.rddd (gun depth) 94+173:00:04:04.333 13 13 13 13 13 13 13 13 .... SHOT TIME GUN DEPTH Note: A '-' sign following the year means that shottime was not received in time. A CPU timetag is placed instead. This sometimes happens at the beginning of the line when the computer and the DMS-2000 are trying to get in sync with each other. No gun was fired, and no data is recorded to the tape. JDAY & TIME Shot Number LINE NAME COMMENTS 286:18:49:17-287:05:41:37 0101-0753 LA01 shot-by-dist 50m 287:11:55:42-288:01:24:01 0105-2414 LARSE01R shot-by-dist 50m 288:01:28:30-288:06:32:37 0101-0935 LARSE01X shot-by-dist 50m 288:06:32:56-288:12:35:17 0101-1068 LARSE01Y shot-by-dist 50m 288:12:36:27-288:21:44:45 0101-0783 LARSETR1 shot-by-dist 50m 288:21:45:16-289:12:10:24 0101-2546 LARSE03 shot-by-dist 50m 289:12:11:30-290:02:37:25 0101-2587 LARSE03R shot-by-dist 50m 290:02:38:46-290:04:59:09 0101-0494 LARSETR2 shot-by-dist 50m 290:05:17:27-291:02:54:01 0101-3215 LARSE02 shot-by-dist 50m 291:01:54:58-291:19:56:51 0101-0822 LARSE02R shot-by-time 90 secs. 291:20:52:55-292:04:04:19 0101-1369 LARSE02X shot-by-dist 50m 292:04:05:21-292:12:31:41 0101-1619 LARSE02Y shot-by-dist 50m 292:13:29:27-292:17:50:16 0101-0883 LARSE02Z shot-by-dist 50m 292:17:51:16-292:23:49:10 0101-1174 LARSETR3 shot-by-dist 50m 292:23:51:10-293:06:40:04 0101-1327 LARSE01A shot-by-dist 50m 293:06:40:41-293:13:56:16 0101-1407 LARSE01B shot-by-dist 50m 293:14:00:13-293:14:43:08 0101-0126 LARSE04 shot-by-dist 50m 293:14:43:08-293:16:44:02 0101-0462 MARSE04 shot-by-dist 50m 293:18:35:45-294:04:31:30 0101-1885 LARSE06 shot-by-dist 50m Partial CO2: Instrument: L-DEO PCO2 Group PCO2 Analysis Instrument Logging: as is. Checking: none Chief scientist's final data: none. Lamont database: merged data with final navigation. FORMAT: 94+036:22:35:00.000 S 21 31.0624 W 31 27.2926 94036.9360 Yr Day Hr Mn Second Lat Lon YrDay.frac 2033.8 2033.8 1014.0 34.64 33.8 419.9 404.5 28.41 Equil 28.2 IR_1 IR_2 Baro CellT Flow VCO2 pCO2 Eq_T Type SeaT YrDay.frac = Time of analysis IR_1 = CO2 signal (mv) IR_2 = CO2 signal (mv) Baro = IR Cell pressure (mbar) CellT = IR Cell temperature (deg C) Flow = Sample/Standard gas flow rate through IR cell (ml/mn) VCO2 = Concentration of CO2 in dry gas sample (preliminary value) (ppm) pCO2 = Partial pressure of CO2 in water-saturated air at temperature of equilibration (uatm); (or residual of 2nd order fit if standard (calibration) gas) Eq_T = Equilibration temperature (deg C) Type = Type of analysis [Equil= equilibrated seawater, Airi= atmospheric air, Stdn= calibration gas] SeaT = Sea Surface Temperature, measured using thermistor on ship's keel (depth= ?? meters) (deg C) DAY TIME COMMENTS 286 1530 beginning of the cruise ; started logging/processing 294 1600 end of cruise ; stopped logging WEATHER STATION: Instrument: R.M/. Young Precision Meteorological Instruments 26700 Series Logging: 1 minute interval Checking: none Chief scientist's final data: as is. Lamont database: as is. FORMAT: wx.rddd Port bird is bird #1; starboard bird is bird #2. 94+022:00:00:00.244 9.3 15.4 13.2 21.1 271 261 date time wsi1 wss1 wsm1 wsx1 wdc1 wds1 6 12.6 15.9 15.6 20.7 261 253 6 66.7 66.7 wdm1 wsi2 wss2 wsm2 wsx2 wdc2 wds2 wdm2 tcur tavg 66.5 67.0 66 58 68 1016.8 tmin tmax rh rhn rhx baro wsi1/2 = wind speed, instantaneous, bird #1/#2 wss1/2 = wind speed, 60 second average, bird #1/#2 wsm1/2 = wind speed, 60 minute average, bird #1/#2 wsx1/2 = wind speed, 60 minute maximum, bird #1/#2 wdc1/2 = wind direction, current, bird #1/#2 wds1/2 = wind direction, 60 second average, bird #1/#2 wdm1/2 = wind direction, 60 minute average, bird #1/#2 tcur = temperature, current tavg = temperature, 60 minute average tmin = temperature, 60 minute minimun tmax = temperature, 60 minute maximum rh = relative humidity rhn = relative humidity, 60 minute minimum rhx = relative humidity, 60 minute maximum baro = barometric pressure DAY TIME COMMENTS 286 1530 beginning of the cruise ; started logging 294 1600 end of cruise; stopped logging KSS-30 GRAVITY: Instrument: Bodenseewerke KSS-30 marine gravity meter Logging: 6 second intervals Merge with navigation: calculate Eotvos correction and Free Air Anomaly. Checking: Visual check of plot of data to determine satisfactory Eotvos corrections, reject spikes of data at turns. Velocity smoothing: 5 point running average throughout the cruise Processing: The KSS-30 times tag is first adjusted for the filtering delay. For "Seastate" setting 2, the delay due to filtering is 75 seconds. Thus75 seconds are subtracted from the time tag and a new, adjusted time is computed. A smooth KSS-30 gravity mgal value at one minute interval is calculated on 00 second of the minute by computing the unweighted mean values from the raw values that lie between +- 30 seconds of 00 seconds of the minute. Calculation: eotvos_corr = 7.5038 * vel_east * cos(lat) + .004154 * vel*vel corrected_grv = raw_grv + eotvos_corr - drift - dc_shift faa = corrected_grv - theoretical_grv Chief scientist's final data: Observed, Eotvos, Free Air Anomaly value at 00 seconds of each minute. 1980 theoretical gravity formula: Y0= 978.0327 x ( 1 + .0053024 x sin( Q ) x sin( Q ) - .0000058 x sin( 2 x Q ) x sin( 2 x Q ) ) FORMAT: vk.nddd yy+ddd:hh:mm:ss.mmm N 10 20.1234 W 120 23.1234 1980 77.1 yr. day time lat. lon. theog FAA 979317.5 64.1 1.5 10.2 -1.7 9.7 -1.6 9.8 raw_grav eotvos drift dc_shift raw_vel smo_vel Lamont database: Free Air Anomaly value at 00 seconds of each minute. 1930 International gravity formula. Note: A '-' sign after the year in the record signifies a flagged record due to turn. As a result of the discussion among the MG&G group, Lamont Data Reduction will use Port's Gravity Referenced Value without Potsdam correction for gravity data sent to MG&G data base at Lamont. Further discussion also revealed that 1980 theoretical gravity formula has incorporated Potsdam correction in its formula. At the start of the cruise, KSS-30 platform was found turned off. As a result, there is no data until the start of JD 164. DAY TIME COMMENTS 286 1530 started data processing 294 1600 end of cruise ; stopped data processing BGM-3 GRAVITY: Instrument: Bell Aerospace BGM-3 marine gravity meter Logging: 1 second intervals Merge with navigation: calculate Eotvos correction and Free Air Anomaly. Checking: Visual check of plot of data to determine satisfactory Eotvos corrections, reject spikes of data at turns. Velocity smoothing: 5 point running average throughout the cruise. Processing: Since current BGM-3 output has double counts every few minutes the following scheme has been implemented until the hardware and interface code has been fixed: (1) Run a 1 minute Gaussian filter through the data. This will narrow the output spikes and make them stand out better. Output interval has been hard-wired to every 15 seconds. (2) Pass the output through filter1d (see gmtsystem) using - FG480 (an 8 minute Gaussian filter with robust option, i.e., ignore "outlier" points (i.e. the spikes). Calculation: eotvos_corr = 7.5038 * vel_east * cos(lat) + .004154 * vel*vel corrected_grv = raw_grv + eotvos_corr - drift - dc_shift faa = corrected_grv - theoretical_grv Chief scientist's final data: Observed, Eotvos, Free Air Anomaly value at 00 seconds of each minute. 1980 theoretical gravity formula: Y0= 978.0327 x ( 1 + .0053024 x sin( _) x sin( _) - .0000058 x sin( 2 x _) x sin( 2 x _) ) FORMAT: vt.nddd yy+ddd:hh:mm:ss.mmm N 10 20.1234 W 120 23.1234 1980 77.1 yr. day time lat. lon. theog FAA 979317.5 64.1 1.5 10.2 -1.7 9.7 -1.6 9.8 raw_grav eotvos drift dc_shift raw_vel smo_vel Lamont database: Free Air Anomaly value at 00 seconds of each minute. 1930 International gravity formula. Note: A '-' sign after the year in the record signifies a flagged record due to turn. As a result of the discussion among the MG&G group, Lamont Data Reduction will use Port's Gravity Referenced Value without Potsdam correction for gravity data sent to MG&G data base at Lamont. Further discussion also revealed that 1980 theoretical gravity formula has incorporated Potsdam correction in its formula. DAY TIME COMMENTS 286 1530 started data processing 294 1600 end of cruise ; stopped data processing PRE-CRUISE GRAVITY TIE-IN: Port: Dutch Harbor, Alaska, U.S.A. Date: July 6, 1994 (JD 187) Operator: Bruce A. Francis Reference Station: ACIC 2178-1 Reference Value: 981552.07 mGals Pier/Ship's position: R/V Ewing was at the pier by the Delta Western Warehouse. Moved here on July 6th to take on fresh water. Gravity meter: L & R Model G, serial number 237. Temperature of meter: 49 oC. Readings and Calculations: TIME LOCATION L&R READING G Potsdam Corr? 2015Z Pier 5046.64+- .05 2032Z Ref 5046.43+- .05 981552.07 NO! 2042Z Pier 5046.62+- .05 TIME GRAVITY G READING 2042Z BGM-3 981564.3 2042Z KSS-30 1396.08 Pier reading 2.8 m above waist deck. Waist deck is 5.5 m above gravity meter. Difference between pier and gravity meter : 5.5 + 2.8 = 8.3 m. Lacoste difference in LR units: delta_LR = pier_LR - ref_LR 0.19 = 5046.62 - 5046.43 Difference in mgal: ( 1 LR unit = 1.06 mGals ) delta_mgal = delta_LR x constant 0.2 = 0.19 x 1.06 Pier gravity value in mgal: ref_val = G (+13.6 if Potsdam corrected) pier_grv_val = ref_val + delta_mgal 981552.27 = 981552.07 + 0.2 Height correction: Height correction in mGals: note: free-air constant of +0.31 mGals per meter going towards the center of earth; -0.31 mGals per meter going away. hgt_corr = hgt x constant 2.57 mGals = 8.3 x 0.31 mGals/m Gravity at gravity meter level in mGals: grv_at_meter_level = pier_grv_val + hgt_corr 981554.84 = 981552.27 + 2.57 KSS-30: KSS-30 value was smooth and time adjusted by 75 secs. KSS_grav_val = kss_unbiased_output + bias 981556.37 = 1396.08 + 980170.29 Mistie in mGals: mistie = KSS_grv_val - grv_at_meter_level 11.53 = 981556.37 - 981554.84 Drift in mGals since last tie: prev_mistie: 15.6 mGals on date May 20,1994 (JD 140) drift = mistie - prev_mistie -4.07 = 11.53 - 15.6 ==> DC Shift = prev_mistie - bias = 15.6 - 980170.29 = -980154.69 Drift/Day = drift / (tot. # of day) = -4.07 / (187-140) = -0.0866 mGals/day BGM-3: BGM_filt_grv = ( scale factor x counts ) + bias = 979537.0 using s.f. 5.0940744 and bias 8526800, filter width 360. ( 6 minutes) Mistie in mGals: mistie = BGM_grv_val - grv_at_meter_level 9.5 = 981564.3 - 981554.84 Drift in mGals since last tie: prev_mistie: 9.83 mGals on date May 20, 1994 (JD 140) drift = mistie - prev_mistie -0.3 = 9.5 - 9.83 ==> DC Shift = prev_mistie = 9.83 Drift/Day = drift / (tot. # of day) = -0.3 / (187 - 140) = -0.0064 mgals/day POST-CRUISE GRAVITY TIE-IN: Port: Balboa, Canal Zone, Panama Date: 26-27 November, 1994 (JD 330-331) Operator: Bruce A. Francis Reference Station: The site is on the sidewalk on the west of the Captain of the Port building, in front of main entrance. The station was made in the middle of the circular concrete section on the sidewalk. Date: 01 Nov. 1971 Position: N 8o 57.60' W 79o 33.81' Pier/Ship's position: R/V Ewing was docked at Pier 16. The tie point is midship, port side. Gravity meter: L & R Model G, serial number 237. Temperature of meter: 49 oC. Readings and Calculations: TIME LOCATION L&R READING G Potsdam Corr? JD 330 1915Z Pier 1919.835 +- .05 JD 330 2047Z Ref. 1920.810 +- .05 978224.1 7 YES!! JD 330 2055Z Pier 1919.845 +- .05 Note: Large tide variation in this port, and at the time of the measurement above it was difficult to note "C" deck height. It is only good to establish pier value. TIME GRAVITY G READING JD 331 1415Z BGM-3 978252.06 JD 331 1415Z KSS-30 1920.99 At 1415Z "C" deck was 1.52 m BELOW pier. "C" deck is 5.5 m above gravity meter. Difference between pier and gravity lab: 5.5 + 1.52 = 7.02 m Lacoste difference in LR units: delta_LR = pier_LR - ref_LR -1.03 = 1919.84 - 1920.81 Difference in mGals: ( 1 LR unit = 1.0690 mGals ) delta_mgal = delta_LR x constant -1.1 = -1.03 x 1.0690 Pier gravity value in mGals: rev_val = G + 13.6 if IT IS Potsdam corrected. pier_grv_val = ref_val + delta_mgal + 13.6 978236.67 = 978224.17 + (-1.1) + 13.6 Height correction: Height correction in mGals: note: free-air constant of +0.31 mGals per meter going towards the center of earth; -0.31 mGals per meter going away. hgt_corr = hgt x constant 2.18 mGals = 7.02 x 0.31 mGals/m Gravity at gravity meter level in mGals: grv_at_meter_level = pier_grv_val + hgt_corr 978238.85 = 978236.67 + 2.18 KSS-30: KSS_grav_val = kss_unbiased_output + bias 978249.3 = -1920.99 + 980170.29 Mistie in mGals: mistie = KSS_grv_val - grv_at_meter_level 10.45 = 978249.3 - 978238.85 Drift in mGals since last tie: prev_mistie: 11.31 mGals on date Oct. 23, 1994 (JD 296) drift = mistie - prev_mistie -0.86 = 10.45 - 11.31 ==> DC Shift = prev_mistie - bias = 11.31 - 980170.29 = -980158.98 mGals Drift/Day = drift / (tot. # of day) = -0.86 / (331-296) = -0.02457 mGals/day BGM-3: BGM_filt_grv = ( scale factor x counts ) + bias = 979537.0 using s.f. 5.0940744 and bias 8526800. The count was filtered with a 60 filter width, run thru filter1d -FG480, and s_bgm Mistie in mGals: mistie = BGM_grv_val - grv_at_meter_level 13.21 = 978252.06 - 978238.85 Drift in mGals since last tie: prev_mistie: 12.02 mGals on date Oct. 23, 1994 (JD 296) drift = mistie - prev_mistie 1.19 = 13.21 - 12.02 ==> DC Shift = prev_mistie = 12.02 Drift/Day = drift / (tot. # of day) = 1.19/ (331-296) = 0.034 mgals/day APPENDIX 5. Software for Plotting Hydrosweep Multi-Beam Bathymetry Data The Hydrosweep data are in a format given below. They may be plotted using software described in this appendix. MBIO Data Format ID: 5 Format name: MBF_HSATLRAW Informal Description: Raw Hydrosweep Attributes: Hydrosweep DS, 59 beam, bathymetry and back scatter, ASCII, Atlas Electronik. So, first thing you have to do is to uncompress them. The command in UNIX is as follows: % uncompress 9414hs.d* ( for a global uncompress of all the HS data) Note: A compressed file is approximately 1/3 the original size. So you might want to make sure that you have enough disk space first. (Written by Dave Caress and Dale Chayes) Dear Colleague: A new release of the MB-System software is now available via anonymous ftp. MB-System is a software package for UNIX computing environments consisting of programs which manipulate, process, list, or display multibeam bathymetry and side scan data. MB-System is being developed at the Lamont-Doherty Earth Observatory of Columbia University with support from the National Science Foundation, SeaBeam Instruments, and Antarctic Support Associates. The new version, 4.1, replaces the previous release of version 3.4 in December, 1993. This release includes many improvements to the package. Among the most significant changes are: - MB-System now handles side scan as well as per-beam bathymetry and the associated beam amplitudes (the current generation of multibeam sonars all produce bathymetry, average beam amplitudes, and high resolution side scan in a single data stream). - MB-System now handles data formats with both across track and along track distances for each bathymetry beam and side scan pixel (vital for data from such sonars as the SeaBeam 2112 and the Elac Bottomchart). - MB-System now handles shallow water data properly. - MB-System now includes support for many new data formats, including: SeaBeam SIO swathbathy format SeaBeam 2000 SIO swathbathy bathymetry format SeaBeam 2000 SIO swathbathy sidescan format SeaBeam URI format in Vax byte order Hydrosweep URI format in Vax byte order HMR-1 processed data format Simrad EM12 processed data from the RRS Darwin Simrad EM1000 raw data Elac Bottomchart UNB format Reson Seabat 9001 UNB format - The graphical tools (mbedit and mbvelocitytool) are now coded using the Motif widget set, giving the code greater portability. Xview based versions are still available for users hopelessly stuck on Sun workstations running under the old operating system. - The macros (mbm_plot and mbm_grdplot) work better and generate more pleasing first cut plots. - The gridding program (mbgrid) now allows both weighted mean and median filter gridding. The optional interpolation in regions with no data is now performed using the same minimum curvature algorithm developed by Walter Smith and Paul Wessel for the GMT program surface. - The swath contouring program (mbcontour) now has two contouring algorithms. The first is the original "ping-to-ping" contouring approach which is fast but works poorly when nearby pings overlap. The new algorithm constructs a triangular network out of the bathymetry points and contours that with no assumptions about order in the data; this method is slower but produces better maps in many cases. - Improved memory handling has greatly increased the reliability of programs such as mbswath and mbgrid. - The program mbswath can generate swath color fill plots with shading derived from beam amplitude values. - MB-System proper now consists entirely of code written in C (the real-time pen plotting code still depends on some FORTRAN routines). - Many, many less prominent refinements and bug fixes. To obtain the compressed tarfile of the directory structure containing the source code, do the following: % ftp lamont.ldgo.columbia.edu Name: anonymous Password: your_email_address ftp> cd pub/swath_data ftp> binary ftp> get README ftp> get MB-System.4.1.tar.Z ftp> get annual.Z ftp> quit To uncompress: % uncompress *.Z To extract the directory structure, move the MB-System tar file to a disk with at least 50 MBytes of free space and do the following: % tar xvf MB-System.4.1.tar Information and installation instructions are found in the file mbsystem/README. There are some additional files available by anonymous ftp that may be of interest: mbedit.xview.4.1.tar.Z mbvelocitytool.xview.4.1.tar.Z MB-SystemExamples4.0.tar.Z The first two contain source code and fully linked executables for Xview (Sun SPARC) versions of two interactive graphical tools, mbedit and mbvelocitytool. The third contains some sample data files and example shellscripts demonstrating the use of some of the MB-System programs. In the next few months, we expect our development effort will focus on the following issues: - Adding a few additional data formats already requested (SIO swathbathy Hydrosweep, raw HMR-1, raw Simrad EM12). - Expanding the MB-System examples into a full, proper tutorial. - Building a mouse driven GUI environment for most-used MB-System utilities. - Developing or adapting sidescan mosaicing capability. - Developing a navigation/heading/pitch/heave/roll data editor. When corresponding, please email to both of us, as one of us is generally out of town or otherwise unavailable at any given time. We will do our best to be responsive to bug reports and suggestions for improvements. Cheers, Dave Caress and Dale Chayes David W. Caress SeaBeam Instruments 141 Washington Street East Walpole, MA 02037 (also at Lamont-Doherty Earth Observatory) caress@seabeam.com or caress@ldeo.columbia.edu voice: 1-800-SEABEAM or (508) 660-6000 fax:(508) 660-6061 Dale N. Chayes Lamont-Doherty Earth Observatory of Columbia University Route 9W, Palisades, N.Y. 10964 dale@ldeo.columbia.edu voice: (914) 365-8434 fax:(914) 359-6940 FIGURE CAPTIONS Fig. 7. Near-trace (ch. 150) constant offset section for Lines LARSE01R and LARSE02. As described in text processing included band pass filtering, automatic gain control (AGC), and water column mute. Figures 7a and 7b show Line LARSE01R and Figures 7c and 7d show Line LARSE02. Fig. 8. Near-trace (ch. 150) constant offset section for Lines LARSE03 and LARSE06. As described in text processing included band pass filtering, automatic gain control (AGC), and water column mute. Figures 8a and 8b show Line LARSE03 and Figures 8c and 8d show Line LARSE06. Fig. 9. Near-trace (ch. 150) constant offset section for Lines TR1A and B, TR2, and TR3. As described in text processing included band pass filtering, automatic gain control (AGC), and water column mute. Figure 9a show Lines TR1A and TR2. Figure 9b shows Lines TR1B and TR3. 1 47 63