Southeastern U. S. Seismic Network Bulletin 14A Hypocenter Listing from Southeastern U. S. Seismic Network Bulletins No. 1 - 14 (July, 1977 to July, 1984) Compiled and Edited by M. S. Sibol and G. A. Bollinger Seismological Observatory Department of Geological Sciences Virginia Polytechnic Institute and State University Blacksburg, Virginia 24061 April 1985 CONTRIBUTORS Carolina Power & Light Company E. I. DuPont de Nemours & Co., Inc. University of Florida Geological Survey of Alabama Georgia Institute of Technology Georgia Southwestern College Memphis State University University of South Carolina South Carolina Electric and Gas Company Tennessee Valley Authority Union Carbide Corporation United States Geological Survey Virginia Division of Mineral Resources Virginia Polytechnic Institute and State University Washington and Lee University West Virginia University SPONSORS National Sciences Foundation Nuclear Regulatory Foundation United States Geological Survey Georgia Power Company Virginia Electric & Power Company Southeastern U. S. Seismic Network Bulletin No. 14A April, 1985 HYPOCENTER LISTING FROM SOUTHEASTERN U. S. SEISMIC NETWORK BULLETINS NO. 1 - 14 (JULY, 1977 THROUGH JUNE, 1984) Compiled and Edited by M. S. Sibol and G. A. Bollinger Seismological Observatory Department of Geological Sciences Virginia Polytechnic Institute and State University Blacksburg, Virginia, 24061 Major Revisions and Relocations Submitted by P. Talwani, Scott Stihler, and J. Rawlins Geology Department University of South Carolina Columbia, South Carolina, 29208 Arch C. Johnston, Don Reinbold, and Steve Brewer Tennessee Earthquake Information Center Memphis State University Memphis, Tennessee, 38152 Leland Timothy Long, Russell Propes, Karl-Heinz Zelt, and Jeih-San Liow School of Geological Sciences Georgia Institute of Technology Atlanta, Georgia, 30332 OVERVIEW The enclosed event listing (Appendix D) gives the hypocentral, size, and error parameters for 1060 seismic events reported in Southeastern U. S. Seismic Network (SEUSSN) Bulletins 1 - 14. The time period covered by those Bulletins is from 1 July 1977 through 30 June 1984. The listing includes only those events with a reported magnitude greater than or equal to zero. This listing is available on magnetic tape from the editors. The SEUSSN Bulletin events are divided into three groups. TECTONIC. This group consists of 366 earthquakes not associated with activity near reservoirs. An epicenter map for this group of events is shown in Figure 1. RESERVOIR. This group consists of 534 earthquakes, mostly in South Carolina and Georgia, associated with activity at or near reservoirs. Therefore, these events are believed to be reservoir induced. An epicenter map for this group of events is shown in Figure 2. BLAST. This group contains 160 events considered to be mostly blasts, several of which have been identified with particular quarries (especially in northwestern South Carolina and northeastern Georgia -- Appendix A). The group also contains some events, tectonic or otherwise, for which the supplied location is thought to be unreliable, or are outside of the SEUSSN monitoring area (*). An epicenter map for this group of events is shown in Figure 3. As it is understood that earthquake catalogs are never perfectly complete or error free, the editors ask users of this listing to please notify us of any errors or omissions that they may uncover. Moreover, as this listing will evolve with time, future changes will be reflected in the magnetic tape version of the catalog. (*) The SEUSSN network monitoring area is considered to include all of Florida, Georgia, Alabama, South Carolina, North Carolina, Virginia, West Virginia (south of latitude 39.72 deg. N), Maryland, and Delaware; and includes Tennessee and Kentucky - east of longitude 87 deg. W. FIGURE 1. Epicenter map of 366 southeastern U.S. earthquakes (not associated with activity near reservoirs) reported in SEUSSN Bulletins 1-14 (1 July 1977 through 30 June 1984). These events are in data file TECTONIC.DAT and are listed in Appendix D. FIGURE 2. Epicenter map of 534 southeastern U.S. earthquakes associated with activity near reservoirs reported in SEUSSN Bulletins 1-14 (1 July 1977 through 30 June 1984). These events are in data file RESERVOIR.DAT and are listed in Appendix D. FIGURE 3. Epicenter map of 160 southeastern U.S. events (mostly blasts) reported in SEUSSN Bulletins 1-14 (1 July 1977 through 30 June 1984). These events are in data file BLAST.DAT and are listed in Appendix D. MAGNETIC TAPE PARAMETERS The tape was written on a DEC PDP 11/34 minicomputer using the RSX11M V.4.0 operating system. The parameters for files on the tape are: Tape Type: Nonlabeled Recording Mode: ASCII Density: 1600 bpi Block Length (Size): 5280 bytes Record Length: 80 or 132 bytes NOTE: record length depends on file type - see following section. FILE ORGANIZATION Events are grouped in four files. Those files are: 1. A chronological listing of tectonic (non-reservoir related) earthquakes (this file is called TECTONIC.DAT), 2. A chronological listing of reservoir associated earthquakes (RESERVOIR.DAT), 3. A chronological listing of events that have been classified as either probable or definite blasts, as being of unknown origin (but thought to be non-tectonic), or that were reported in the Bulletin but are outside the SEUSSN monitoring area (BLAST.DAT), 4. A list of all of the events in TECTONIC.DAT, RESERVOIR.DAT, and BLAST.DAT, respectively (ALLSEUSSN.DAT). The tape contains a short FORTRAN program with the file name of RWSEUSSN.FTN (Appendix C). That program reads an input data file, written in the SEUSSN format, and outputs the data in a tabular form (see for example the printed listing of events in Appendix D). Although this program is somewhat system dependent, it should serve as both an example and as a foundation from which the general user may write similar or more involved programs. The tape contains a copy of an output event listing (called EQTABLE.TXT; Appendix D) that was generated by running RWSEUSSN.FTN. The tape also contains a file which is a copy of this documentation (called BULL14A.TXT). The format of these two files (EQTABLE.TXT and BULL14A.TXT) is close to system independent with the first character of each record being a control character. Finally, included with the tape is a directory of the files that have been placed on the tape. This directory includes the name, number, number of blocks, block length, and record length, of each file on the tape. The directory file is the last file on the tape (DIRECTORY.TAP) and a hardcopy version is supplied with the tape. Thus, files found on the tape include: TECTONIC.DAT (data file - record length = 80) RESERVOIR.DAT (data file - record length = 80) BLAST.DAT (data file - record length = 80) ALLSEUSSN.DAT (data file - record length = 80) RWSEUSSN.FTN (FORTRAN file - record length = 80) EQTABLE.TXT (text file - record length = 132) BULL14A.TXT (text file - record length = 132) DIRECTORY.TAP (text file - record length = 80) DATA FORMAT Information supplied with each event includes such common locational parameters as the number of phase arrival times used to compute the location, the distance from the epicenter to the closest recording station, the largest azimuthal gap in the recording stations, and the RMS of the residuals of the arrival time data. The SEUSSN format is generally patterned after the hypocenter output line of such locational programs as HYPO71 and HYPOELLIPSE. As an example of the SEUSSN data format, consider the first event in TECTONIC.DAT. This event was located in southeastern Tennessee and occurred on 27 July 1977 (see Appendix D). In the data file, the event is written as: Columns 1-43; 'TN 770727220321.235.38984.35612.6 3.5N3.2N5' Columns 44-79; '22 58 670.3 1.8+37 1.1 3.0BCBDV10 01' NOTE: this event is used as an example in the following discussion. The SEUSSN data format may be read using the following FORTRAN statements: INTEGER*4 STATE,CODE,IYR,IMO,IDAY,IHR,IMIN,FIXD, & SRCMB,SRCMLD,INT,NPH,IDMIN,IGAP,IAZM1,QELL, & QSOL,QSTA,QDIS,SRCLOC,VLAST,VFRST REAL OTSEC,DLAT,DLON,DEPTH,AMD,AMLD,RMS,ERH1,ERH2,ERZ READ(1,2) STATE,CODE,IYR,IMO,IDAY,IHR,IMIN,OTSEC, & DLAT,DLON,DEPTH,FIXD,AMB,SRCMB,AMLD,SRCMLD,INT, & NPH,IDMIN,IGAP,RMS,ERH1,IAZM1,ERH2,ERZ,QELL, & QSOL,QSTA,QDIS,SRCLOC,VLAST,VFRST 2 FORMAT(A2,A1,5I2,F4.1, & 2F6.3,F4.1,A1,2(F3.1,A1),A1, & I2,2I3,F3.1,F4.1,I3,2F4.1,A1, & 3A1,A1,A3,I2) where: STATE (A2; columns 1 - 2) indicates the state in which the event was located. (EXAMPLES: 'TN', or 'VA') CODE (A1; column 3) is a code used to classify an event. For the case of events that are thought to be reservoir related, codes indicate the appropriate reservoir. For events thought to be blasts, codes indicate the quarry (if known). A listing of codes and their definitions may be found in Appendix A. (EXAMPLES: ' ', or 'E') IYR,IMO,IDAY,IHR,IMIN,OTSEC (5I2,F4.1; columns 4 - 17) specify the origin time (the year, month, day, hour, minute, and seconds, respectively, UCT) of the event. (EXAMPLES: '770727220321.2', or '820523000043.6') DLAT,DLON (2F6.3; columns 18 - 29) are the computed decimal latitude (+ north) and longitude (+ west), respectively, for the event. (EXAMPLES: '35.38984.356', or '35.7 82.3 ') DEPTH,FIXD (F4.1,A1; columns 30 - 34) specifies the depth of the computed hypocenter and whether or not the depth was fixed during computation. (EXAMPLES: '12.6 ', or ' 5.0F') AMB,SRCMB,AMLD,SRCMLD (2(F3.1,A1); columns 35 - 42) indicate the magnitudes Mb(Lg), and/or MLD (local or duration magnitude) determined for the event. NOTE: this listing includes only those events with a reported magnitude greater than or equal to zero. (EXAMPLES: '3.5N3.2N', or ' 1.1V') INT (A1; column 43) indicates the intensity (MM) for felt events. Values are designated by either a numeric character or an F, which implies that the event was felt but no intensity has been assigned. NOTE: some of the event listings have been supplemented with intensities assigned by the USGS in their annual catalogs United States Earthquakes and other similar USGS publications. (EXAMPLES: '5', or 'F') NPH,IDMIN,IGAP,RMS (I2,2I3,F3.1; columns 44 - 54) specify some common locational parameters used to estimate locational quality. NPH is the number of phase arrival times used in locating the event; IDMIN is the distance in kilometers from the epicenter to the nearest recording station; IGAP, is the largest azimuthal separation in degrees between recording stations; and RMS is the root-mean-square of the weighted traveltime residuals (Lee and Lahr, 1974; Lahr, 1981). (EXAMPLES: '22 58 670.3', or ' 65 0.1') ERH1,IAZM1,ERH2,ERZ,QELL (F4.1,I3,2F4.1,A1; columns 55 - 70) indicate computed error measures often specified in earthquake location programs such as HYPO71 (Lee and Lahr, 1974) and HYPOELLIPSE (Lahr, 1981). If the solution specifies an error ellipse (generated by projecting an error ellipsoid onto horizontal and vertical surfaces) then ERH1, and ERH2, are the semi-major and semi-minor axes of the horizontal ellipse, respectively, and IAZM1 is the bearing, with respect to north, of the semi-major axis (ERH1). ERZ is the horizontally projected axis of the error ellipsoid. If the computed solution specifies a single horizontal error (for example, ERH from HYPO71) then both ERH1 and ERH2 are this value and IAZM1 is defined as 360 degrees. If the solution specifies a vertical error (for example, ERZ from HYPO71), then this error is entered for ERZ. QELL is the HYPOELLIPSE error ellipse quality. (EXAMPLES: ' 1.8+37 1.1 3.0B', or ' 5.1360 5.114.2 ') QSOL,QSTA,QDIS (3A1; columns 71 - 73) indicate the solution quality of the computed hypocenter as described for HYPO71 and HYPOELLIPSE. QSOL represents the solution quality and is the average of QSTA and QDIS. QSTA is a measure of the statistical quality of the solution, while QDIS is a measure of the distribution of stations around the hypocenter. (EXAMPLES: 'CBD', or 'D ') SRCLOC (A1; column 74) indicates the source organization, institution, or reference from which the most recent hypocentral information was received. If the event has not been relocated but has been reclassified (e.g., from a quake to a blast, or from a tectonic quake to a reservoir related quake) then the organization that reclassified the event is cited. A listing of the abbreviations employed and their definitions may be found in Appendix B. (EXAMPLES: 'V', or 'S') VLAST (A3; columns 75 - 77) specifies the volume of the SEUSSN bulletin in which the most recent hypocentral and/or magnitude information was reported. If the event has not been relocated but has been reclassified (e.g., from a quake to a blast, etc.) then the volume in which the new classification was announced is cited. NOTE: this variable will be blank if the event has not been reclassified, relocated, or the magnitude recomputed. Also, the variable may contain letter characters (e.g., '10A') and therefore should be read as A3 (if this is a problem, it is possible to read this string as two variables (i.e., read as I2,A1)). (EXAMPLES: '10 ', or '14A') VFRST(I2; columns 78 - 79) specifies the volume of that SEUSSN bulletin in which the event and arrival time data were originally reported. NOTE: in some cases, arrival time data were not supplied by the source organization, or in the case of most of the reservoir events, the large number of events involved did not allow for the inclusion of arrival time data. (EXAMPLES: '01', or '12') If there are any questions concerning the formating of the tape or the event listings, please contact either Matt Sibol (703-961-4707 or 703-961-5036) or G. A. Bollinger (703-961-6729) at Virginia Tech. REFERENCES Coffman, J. L., C. A. von Hake, and C. W. Stover, (1982), Earthquake History of the United States, Publication 41-1 (revised edition with supplement), U.S. Dept. of Commerce, NOAA, and the U.S. Geological Survey, Boulder, Co, 258 p. Herrmann, R. B., C. A. Langston, and J. E. Zollweg, (1981), THE SHARPSBURG, KENTUCKY, EARTHQUAKE OF JULY 27, 1980, Bull. Seism. Soc. Am., Vol. 72, pp. 1219-1239. Lahr, J. C., (1980), HYPOELLIPSE/MULTICS: A computer program for determining local earthquake hypocentral parameters, magnitude, and first-motion pattern, U.S. Geological Survey Open-File Report 80-59, 59 p. Lee, W. H. K., and J. C. Lahr, (1974), HYPO71: A computer program for determining hypocenter, magnitude, and first motion pattern of local earthquakes, United States Geological Survey Open-File Report 75-311, Revised: January 1974, 134 p. Stover, C. W., J. H. Minsch, P. K. Dunbar, and G. W. Baldwin, (19XX), Earthquakes in the United States, published quarterly (with annual summaries) by the U.S. Geological Survey. Stover, C. W., B. G. Reagor, and S. T. Algermissen, (1984), United States Earthquake Data File, U.S. Geological Survey Open-File Report 84-225, 123 p. APPENDIX A Codes used to classify events found in either the reservoir data file listing or the blast data file listing. For the reservoir event listing (RESERVOIR.DAT); C - Clark Hill Reservoir Events H - Lake Hartwell Events J - Lake Jocassee Events K - Lake Keowee Events M - Monticello Reservoir Events R - Richard B. Russel Reservoir Events S - Lake Sinclair Events For the blast event listing (BLAST.DAT); A - Pacolet, SC, Vulcan Materials Quarry (34.912N, 81.782W) B - Greenwood, SC, Lone Star Quarry (34.313N, 82.141W) C - Liberty, SC, Vulcan Materials Quarry (34.773N, 82.663W) D - Lakeside, SC, Vulcan Materials Quarry (34.772N, 82.358W) E - Cayce, SC, Martin Marietta Quarry (33.973N, 81.049W) F - Columbia, SC, Lone Star Quarry (33.970N, 81.037W) G - Anderson, SC, Interstate Highway (approximate location: 34.48N, 81.65W) H - Dreyfus, SC, Lone Star Quarry (34.128N, 81.121W) I - North Columbia, SC, Martin Marietta Quarry (37.777N, 81.113W) J - Blair, SC, Lone Star Quarry (34.417N, 81.395W) P - Indicates the computed location for the event is unreliable due to the quality or quantity of arrival time data U - Indicates the event is of unknown origin but for one reason or another is thought not to be tectonic or reservoir related (this classification includes events thought to be blasts due to signal characteristic, time of day of occurrence, and/or if the epicenter is near the location of a known operating quarry) X - Indicates events reported in the Bulletin that are considered to be outside the SEUSSN monitoring area APPENDIX B Abbreviations of source organizations, institutions, or references that have been used to categorize events. C - University of South Carolina (Geology Department, University of South Carolina, Columbia, South Carolina, 29208) G - Georgia Institute of Technology (School of Geological Sciences, Georgia Institute of Technology, Atlanta, Georgia, 30332) H - Herrmann, R. B., C. A. Langston and J. E. Zollweg, (1981), THE SHARPSBURG, KENTUCKY, EARTHQUAKE OF JULY 27, 1980, Bull. Seism. Soc. Am., Vol. 72, pp. 1219-1239. N - National Earthquake Information Service (National Earthquake Information Service, U. S. Geological Survey, Branch of Global Seismology and Geomagnetism, Mail Stop 967, Box 25046, Denver Federal Center, Denver, Colorado, 80225) S - United States Geological Survey (U. S. Geological Survey, Branch of Earthquake Tectonics and Risk, Mail Stop 966, Box 25046, Denver Federal Center, Denver, Colorado, 80225) NOTE: this abbreviation is also used to specify USGS periodic catalogs of earthquake locations (United States Earthquakes), USGS Publication 41-1 (1982) (Earthquake History of the United States), and USGS Open-File Report 84-225 (United States Earthquake Data File). T - Tennessee Earthquake Information Center (Tennessee Earthquake Information Center, Memphis State University, Memphis, Tennessee, 38152) V - Virginia Tech Seismological Observatory (Virginia Tech Seismological Observatory, Department of Geological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, 24061) APPENDIX C Following is a listing of the FORTRAN program RWSEUSSN.FTN. Listings of some of the subroutines called by this program (in particular, interactive routines such as PRINTX.FTN, TIMDAT.FTN, and TRUTH.FTN) may be found in SEUSSN Bulletin 10A. A copy of RWSEUSSN.FTN (including subroutines PRINTX.FTN, TIMDAT.FTN, and TRUTH.FTN) is on the tape. APPENDIX D Following is a table of events contained in TECTONIC.DAT, RESERVOIR.DAT, and BLAST.DAT, respectively. This hardcopy listing is available on the tape and is called EQTABLE.TXT. The listing was generated by running the program RWSEUSSN.FTN (Appendix C). Columnar headings for the table are defined as follows: 'St' indicates the state in which the event was located. 'Cd' is a code used to classify an event. For the case of events that are thought to be reservoir related, codes indicate the appropriate reservoir. For events thought to be blasts, codes indicate the quarry (if known). A listing of codes and their definitions may be found in Appendix A. 'Date' specifies the year, month, and day (respectively, UCT) on which the event occurred. 'HrMn Sec' specify the origin time (the hour, minute, and seconds, respectively, UCT) of the event. 'Lat-N Lon-W' are the computed decimal latitude (+ north) and longitude (+ west), respectively, for the event. 'Depth' specifies the depth of the computed hypocenter and whether or not the depth was fixed during computation. 'Mb MLD' indicate the magnitudes Mb(Lg), and/or MLD (local or duration magnitude) determined for the event. NOTE: this listing includes only those events with a reported magnitude greater than or equal to zero. 'In' indicates the intensity (MM) for felt events. Values are designated by either a numeric character or an F, which implies that the event was felt but no intensity has been assigned. NOTE: some of the event listings have been supplemented with intensities assigned by the USGS in their annual catalogs United States Earthquakes and other similar USGS publications. 'NPh Dmin Gap RMS' specify some common locational parameters used to estimate locational quality. NPh is the number of phase arrival times used in locating the event, Dmin is the distance in kilometers from the epicenter to the nearest recording station, Gap, is the largest azimuthal separation in degrees between recording stations, and RMS is the root-mean-square of the weighted traveltime residuals (Lee and Lahr, 1974; Lahr, 1981). 'ERH1 @ AZ1 ERH2 ERZ QE' indicate computed error measures often specified in earthquake location programs such as HYPO71 (Lee and Lahr, 1974) and HYPOELLIPSE (Lahr, 1981). If the solution specifies an error ellipse (generated by projecting an error ellipsoid onto horizontal and vertical surfaces) then ERH1, and ERH2, are the semi-major and semi-minor axes of the horizontal ellipse, respectively, and AZ1 is the bearing, with respect to north, of the semi-major axis (ERH1). ERZ is the vertically projected axis of the error ellipsoid. If the computed solution specifies a single horizontal error (for example, ERH from HYPO71) then ERH1 and ERH2 are this error and AZ1 is defined as 360 degrees. If the solution specifies a vertical error (for example, ERZ from HYPO71), then this error is entered for ERZ. QE is the HYPOELLIPSE error ellipse quality. 'QL S:D' indicate the solution quality of the computed hypocenter as described for HYPO71 (also done for HYPOELLIPSE). QL represents the solution quality and is the average of S and D. S is a measure of the statistical quality of the solution, and D is a measure of the distribution of stations around the hypocenter. 'Source' indicates the organization, institution, or reference from which the most recent hypocentral information was received. If the event has not been relocated but has been reclassified (e.g., from a quake to a blast, or from a tectonic quake to a reservoir related quake), then the organization that reclassified the event is cited. A listing of the abbreviations employed and their definitions may be found in Appendix B. The first three characters following the source organization specify the volume of the SEUSSN bulletin in which the most recent hypocentral and/or magnitude information was reported. If the event has not been relocated but has been reclassified then the volume in which the new classification was announced is cited. This entry may be blank if the event has not been reclassified, relocated, or the magnitude recomputed. The last two numbers in the source specification indicate the volume of the SEUSSN bulletin in which the event was originally reported.