============================================================================= U.S. Department of the Interior, U.S. Geological Survey Format of geophysical data to accompany Scientific Investigations Report 2007-5226 K.J. Ellefsen, B.L. Burton, J.E. Lucius, S.S. Haines, D.V. Fitterman, J.A. Witty, D. Carlson, B. Milburn, and W.H. Langer ============================================================================= 1. Overview This CD-ROM stores the geophysical data that are described in the report SIR 2007-5226. These geophysical data include seismic data, electrical resistivity data, and time-domain electromagnetic data. The formats used to store these three types of data are described here and in accompanying documents. If you find any errors or if you have any questions, please contact: Karl J. Ellefsen U.S. Geological Survey Mail Stop 964, Box 25046 Denver, CO 80225-0046 telephone: 303-236-7032 e-mail: ellefsen@usgs.gov ============================================================================= 2. Format of the seismic data 2.1 Introductory information Five seismic profiles were collected at the field site, and they are labeled AA', CC', DD', FF' and GG'. The locations of these profiles are shown on plate 1 of the report. Each profile consists of either one or two spreads. For seismic profile CC', for example, there are two spreads, which are named CC'_1, and CC'_2. The spreads in the other seismic lines have analogous names. The data for seismic profile CC' are stored in directory LineCC' on the CD-ROM. Within this directory, there are two subdirectories corresponding to its two spreads. Subdirectory CC'_1, for example, contains all data for spread CC'_1. The formats of the data in this subdirectory are described in this section. This description also applies to the data in all other subdirectories, as the formats are identical. ----------------------------------------------------------------------------- 2.2 Format of file lineCC'_1_spr.txt This file contains general information about the spread, such as the receiver (geophone) locations and the source (shot) locations. Here is an extract of this file: Spread name: lineCC'_1 Number of receivers = 48 Rec. Location (m) No. X Y Z 1 25.85 0.16 194.34 2 29.88 0.12 194.36 3 33.91 0.09 194.37 4 37.94 0.06 194.39 5 41.97 0.02 194.40 6 45.99 -0.01 194.42 7 49.99 -0.02 194.43 8 53.96 0.00 194.42 9 57.92 0.03 194.42 10 61.89 0.05 194.42 . . . . 45 201.56 -0.52 194.31 46 205.54 -0.47 194.33 47 209.53 -0.43 194.35 48 213.51 -0.38 194.37 Number of source locations = 12 Number of polarities = 1 Shot Location (m) No. X Y Z Seismogram File 1 0.08 0.09 194.01 stack037.sgy 2 23.84 0.17 194.33 stack040.sgy 3 48.01 -0.03 194.43 stack043.sgy . . . . 11 239.30 -0.24 194.45 stack067.sgy 12 263.31 -0.63 194.55 stack070.sgy File name for travel times: lineCC'_1_pik.txt Because all entries in this file are labeled, only three remarks are necessary. First, some seismic data were collected with only one polarity of the source; in this case, there is only one seismogram file for each shot. Other seismic data were collected with two polarities of the source; in this case, there are two seismogram files for each shot. Second, the coordinate system used to specify the locations of the receivers and the shots pertains to the entire seismic profile. The coordinate system is selected so that x refers to distance along the seismic profile, y to the offset from the profile, and z to the elevation. The units for length are meters. ----------------------------------------------------------------------------- 2.3 Format of seismogram files Near the end of file lineCC'_1_spr.txt is the list of files containing the seismograms. These files are in SEG-Y format, which is a standard format for the seismic data. Detailed information about this format can be obtained from Barry and others (1980). All of these files have the extension "sgy". The byte order for the headers and the traces is little endian (that is, right-to-left), and the traces are written using the IBM convention for floating point numbers (Cohen and Stockwell, 2001). ============================================================================= 3. Format of the electrical resistivity data 3.1 Introductory information Six dc resistivity profiles were collected at the field site, and they are labeled BB', EE', HH', II', JJ’ and KK'. The locations of these profiles are shown on plate 1 of the report. Each profile consists of one spread of 100 electrodes. The data for resistivity profile BB' are stored in directory LineBB' on the CD-ROM. The formats of the data in this subdirectory are described in this section. This description also applies to the data in all other subdirectories, such as LineEE’, as the formats are identical. ----------------------------------------------------------------------------- 3.2 Explanation of SuperSting ASCII files File lineBB’.cmd is used by the SuperSting R8 to determine which combinations of electrodes to use for measurements. This file is provided so that the survey geometry can be duplicated when using a SuperSting R8. Additional information regarding this file and the use of AGISSAdmin.exe, the software that created the file, can be found at the AGI web site http://www.agiusa.com/ . File lineBB’.crs is created by the SuperSting R8 and records the contact resistance for the electrodes. File lineBB’.stg is created by the SuperSting R8 and records the measured data. This “stg” file is used as input into resistivity modeling software such as EarthImager 2D. File lineBB’.trn is a “terrain” file and records the horizontal location and elevation at various places along the profile. It is used as input into resistivity modeling software such as EarthImager 2D. ----------------------------------------------------------------------------- 3.3 Explanation of EarthImager 2D ASCII files File LineBB’_trial.out stores the results of the modeling process, and enough information so that EarthImager 2D can read this file and reproduce the results of the modeling. File LineBB’_trial.stg is a duplicate of the lineBB’.stg file; some information that is not needed for modeling has been deleted at the end of each record. File LineBB'_trial_InvRes10.dat is the resistivity model in X-Z-Value (3 column) format written row-by-row. The “X” value is traverse distance from the start of the line. The “Z” value is the real elevation of a row, if the lineBB’.trn file was provided, or the relative elevation if no “trn” file was used (first row is at 0.0 and deeper rows have increasing more negative values). This file can be used by Golden Software’s Surfer© as an input data file for creation of grids. File LineBB'_trial_InvRes10.bln is a X-Z file (two columns) that can be used by programs such as Golden Software’s Surfer© to “blank out” areas of a resistivity model grid. Specifically, triangular areas in the lower-left and lower-right corners of the grid are “blanked”. The first record has the number of records that follows. The remaining records are “X”, which is the traverse distance along the line, and “Z”, which is either true or relative elevation. File LineBB'_trial_InvRes10.bmp is an image showing the resistivity model. File LineBB'_trial_AllRes10.bmp is an image showing the measured (field) apparent resistivity, the calculated (from the model) apparent resistivity, and an inverted resistivity section (the model). ============================================================================= 4. Format of the time-domain electromagnetic data 4.1 Introductory information Twenty-eight TEM soundings were performed at the field site. The locations of these profiles are shown on plate 1 of the report. All data associated with these soundings (raw and processed) are located in the folder TEM. Included there is a document, TEM_Processing_Flow_Details_Formats.doc, that describes the formats of all the files, as well as data processing flow and file naming conventions. ============================================================================= 5. Disclaimer This compact disc (CD) publication was prepared by an agency of the United States Government. Neither the United States Government nor any agency thereof nor any of their employees makes any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed in this report or represents that its use would not infringe privately owned rights. Reference therein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. Although all data and software published on this CD have been used by the USGS, no warranty, expressed or implied, is made by the USGS as to the accuracy of the data and related materials and (or) the functioning of the software. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of these data, software, or related materials. ============================================================================= 6. References Barry, K.M., Cavers, D.A., and Kneale, C.W., 1980, Recommended standards for digital tape formats in Digital tape standards: Tulsa, Okla., Society of Exploration Geophysicists, p. 22–30. Cohen, J.K., and Stockwell, J.W., 2001, CWP/SU -- Seismic unix release 35 -- A free package for seismic research and processing: Center for Wave Phenomena, Golden, Colo., Colorado School of Mines. =============================================================================