README.1ST FAULTS, LINEAMENTS, AND EARTHQUAKE EPICENTERS DIGITAL MAP OF THE PAHUTE MESA 30’ X 60’ QUADRANGLE, NEVADA U.S. Geological Survey Open-File Report 96-262 ON-LINE USER INSTRUCTIONS Introduction The geologic data associated with this database are distributed in two formats: (1) ARC/INFO ASCII-generate files, and (2) ARC/INFO export files (partially compressed). Included with this release is a plot file that will produce a stand-alone color plot of the database superposed on the Pahute Mesa 1:100,000-scale topographic base map. Also included is extensive map-related informative and interpretive text. The current database was developed in the Geographic Resource analysis Support System (GRASS), a public-domain geographic information system (GIS). (The current release of GRASS and all pertinent documentation are available on Internet from moon.cecer.army.mil [129.229.20.254] under the directory /grass/grass4.1). Uncompressing the Tar File The database was compressed with the GNU utility gzip. If you do not have this utility, it is available from any of the GNU source sites. This software is available for UNIX systems, PCs running DOS, and an executable version for DEC VMS systems. A “tar” utility is also available for all three systems. The command sequences shown below are in UNIX “C” shell (csh). The sequences are the same for other operating systems, but the form of the commands are different. To uncompress the data enter: UNIX% gunzip pmseis.tar To access the data, enter: UNIX% tar vxf pmseis.tar The data should now be available under the directories indicated below. Data Location All the data are found in directories under the directory pmseis. The ARC/INFO ASCII- generate files are located in the directory pmseis/arc/generate. The ARC/INFO export files are located in the directory pmseis/arc/export. The export files, which were created using ARC/INFO version 6.0, are only partially compressed for better portability to non- Unix ARC/INFO platforms. Map-related informative and interpretive text is located in both ASCII (maptext.asc) and encapsulated PostScript (maptext.pst) files in the directory pmseis/text. An HPGL2 plot file (“fig1.hgl”) of “Figure 1” referred to in the map text and a CalComp plot file (“pmflee.plt”) of the entire map database are located in the directory pmseis/plot. Line Map Feature Attribute Coding Alpha and numeric attribute codes are keyed numerically to tagged line map features (i.e., fault, lineament, and caldera lines) in the database. These codes are located in: (1) the ASCII generate files having the extension “.txt”, and (2) the “.aat” INFO files embedded in the ARC/INFO line coverages. Definitions of the alpha codes for line map features are listed below under headings that indicate the ARC/INFO generate “.txt” and coverage “.aat” files the codes are located in. In the case of the coverage .aat files these three-letter codes are listed under the item LINE_TYP. Note that all references to “left” and “right” directions in the definitions (e.g., “down-to-left apparent offset”) apply when viewing in the direction of the digital line feature (i.e., away from the line origin). flts.txt ; faults.aat: Lbb=normal fault; down-to-left apparent offset Rbb=normal fault; down-to-right apparent offset Llo=oblique-slip fault; down-to-left / left-lateral sense of movement Lro=oblique-slip fault; down-to-left / right-lateral sense of movement Rlo=oblique-slip fault; down-to-right / left-lateral sense of movement Rro=oblique-slip fault; down-to-right / right-lateral sense of movement Lss=strike-slip fault; left-lateral sense of movement Rss=strike-slip fault; right-lateral sense of movement Lbx=low-angle (< 30 deg. dip) fault; upper plate on left side Rbx=low-angle fault; upper plate on right side Lst=thrust fault; upper plate on left side Rst=thrust fault; upper plate on right side Lhr=Tertiary(?) landslide slip-surface trace; slide block on left side Rhr=Tertiary(?) landslide slip-surface trace; slide block on right side und=displacement unspecified lins.txt ; lineaments.aat: Blb=lineament in bedrock; associated left-facing geomorphic scarp Brb=lineament in bedrock; associated right-facing geomorphic scarp Bun=lineament in bedrock; existence or facing direction of associated geomorphic scarp unknown Qlb=lineament in Quaternary deposit; associated left-facing geomorphic scarp Qrb=lineament in Quaternary deposit; associated right-facing geomorphic scarp Qun=lineament in Quaternary deposit; existence or facing direction of associated geomorphic scarp unknown calds.txt ; calderas.aat: hrl=caldera topographic wall; basin to left hrr=caldera topographic wall; basin to right und=caldera structural margin Definitions of the numeric codes for line map features are partly given by the accompanying three-letter alpha codes listed in the .txt and .aat files and translated above. The numeric codes, however, serve to make additional distinctions of line features on the basis of other geologic criteria. These additional numeric code definitions are listed below under headings indicating the ARC/INFO generate “.txt” and coverage “.aat” files the codes are located in. In the case of the coverage .aat files these numeric codes are listed under the item SYMBOL. flts.txt ; faults.aat: 1, 4, 7, 10, 12, 23, 24, 25, 28, 31, 34, 37, 40, 43, 46=well-located natural fault or slip- surface trace 2, 5, 8, 26, 29, 32, 35, 38, 41, 44, 47=approximately located or inferred natural fault or slip-surface trace 3, 6, 9, 11, 13, 27, 30, 33, 36, 39, 42, 45, 48=concealed natural fault or slip-surface trace 49, 50, 51=natural fault that offsets Quaternary deposits 14, 17, 20=well-located fault in bedrock that ruptured in response to nuclear testing; existence of fault known prior to nuclear test but reactivation occurred in response to testing 15, 18, 21=approximately located or inferred fault in bedrock that ruptured in response to nuclear testing; existence of fault known prior to nuclear test but reactivation occurred in response to testing 52, 53, 54=fault in Quaternary deposits that ruptured in response to nuclear testing; existence of fault known prior to nuclear test but reactivation occurred in response to testing 55, 56, 57=fault first recognized on the basis of surface rupture due to nuclear testing; includes new ruptures in bedrock or Quaternary deposits resulting from test-induced reactivation of subsurface faults lins.txt ; lineaments.aat: 1, 2, 3=aerial-photo lineaments in Quaternary deposits 4, 5, 6=aerial-photo lineaments in bedrock calds.txt ; calderas.aat: 1=well-constrained caldera structural margin 2=approximately located caldera structural margin 3=inferred or uncertain caldera structural margin 4, 5=topographic wall of caldera Point Map Features Point map data in the current database consist of: (1) earthquake epicenter data, and (2) locations of Southern Great Basin Seismic Network (SGBSN) seismograph stations. The epicenter data have been grouped into one of two data subsets and corresponding generate/coverage groupings (prefixed “seishs” and “seis78”), based on whether the data were derived from the historical Meremonte and Rogers (1987) seismicity catalog or post-7/78 SGBSN catalog, respectively. The “.txt” generate and “.pat” point-coverage files in each grouping give the earthquake magnitude and hypocenter depth corresponding to each epicenter location. The locations of seismograph stations belonging to the SGBSN are given in a separate generate/coverage grouping having the prefix seistaloc. Points of Contact Geologic inquires should be directed to Scott Minor. Technical inquiries can be addressed to Ron Wahl or Scott Minor. Scott Minor / Ron Wahl U.S. Geological Survey P.O. Box 25046, MS 913 Denver, CO 80225 E mail: sminor@ardneh.cr.usgs.gov rwahl@ardneh.cr.usgs.gov (303)236-0303 (Minor) (303)236-1320 (Wahl) FAX (303)236-5690