U.S. GEOLOGICAL SURVEY DIGITAL DATA SERIES DDS-7 Digitized Strong-Motion Accelerograms from North & Central American through 1986 by Linda C. Seekins A. Gerald Brady Catherine Carpenter Nicholas Brown OVERVIEW INTRODUCTION Many agencies are currently collecting and distributing digital strong-motion accelerograms in North America, and many have done so in the past. With their help, we have amassed a data base of 1,477 mostly three-component station recordings from about 500 earthquakes. These data represent all of the available North American and Hawaiian records written by ground-level instruments. They have all been copied into a uniform file format, with one file for each component of the recording station: each file includes information about the earthquake and recording station. The complete set of data files is available on a CD-ROM optical disk. A BRIEF HISTORY OF ACCELEROGRAM CATALOGS The set of reports containing accelerogram listings and processing plots informally called the Blue Book series, published by the California Institute of Technology (Caltech) from 1969 to 1974, was the first major effort to catalog and distribute digital strong-motion-acceleration records. It contained most of the United States records from 1933 through the San Fernando earthquake of February 9, 1971. After its publication, many more digitized analog film records have been compiled, and digital strong-motion recordings as well as the agencies that collect them have proliferated, partly because the interest in strong-motion data has increased and partly because the collection of digital accelerograms is easier now. Modern digital recording systems do not require the expensive and time-consuming step of digitizing film or paper records. All accelerograms recorded on these instruments are preserved (at least initially) in digital form, even those that might have been considered too uninteresting or insignificant to digitize had they been recorded on film. 1 The result is that more agencies with more instruments are producing more strong-motion records. The National Geophysical Data Center (NGDC) distributes the accelerograms provided to it by several agencies, as does the Lamont-Doherty Geological Observatory of Columbia University under the aegis of the National Center for Earthquake Engineering Research (NCEER). THE NEED FOR A NEW CATALOG After the publication of the Caltech's Blue Book series, other catalogs that contained many important acceleration records have been compiled, but none so comprehensive. Our catalog represents an effort to collect and archive together all of the ground-level digital strong-motion accelerograms that have been written at permanent recording stations in North America through the end of 1986. Furthermore, all of these records are now available on one CD-ROM optical disk. In addition to consolidating the records of several agencies, we discovered problems that the publication of this collection should solve. With the passing of time and changes in personnel, some records were misplaced; we are aware of about a dozen that we were unable to find. Another problem, more easily solved, was caused by the rapid obsolescence of computer systems. We encountered major difficulties in trying to read some of the tapes that had been written by now-antiquated computers. In addition, some older tapes were beginning to show signs of deterioration. Some of the records had not been used for such a long time that they were still stored on cards, making them unreadable at the institute that loaned them to us, because it no longer has a card reader. THE RECORDS This collection contains all of the digital strong motion accelerograms that we were able to locate which were written before 1987 at permanent ground-level recording stations located in North America or Hawaii. We also included records from temporary stations that were written by earthquakes of magnitude greater than or equal to 5, or that were located in the data-poor central or eastern regions of the continent, where data are more sparse than in the west. Two exceptions to this are the Oroville, Calif. aftershock sequence of 1975, which would have been excluded had the criteria been strictly applied, and the Enola, Ark. swarm of 1982, part of which was omitted. The Oroville sequence is included because it covers a wide range of magnitudes at small distances. For the Enola swarm, we excluded records from earthquakes of magnitude less than 2.5 because of the large number of recordings. 2 We emphasize that this collection is a ground-level data set. Many of these accelerograms were written on instruments described as "free field". (We use this term here, although a true free-field station is impossible.) Many other records were written on instruments located in basements or on the ground floors of buildings which are so large that they should not be considered free-field recordings. The user who must avoid recordings that contain structural noise should be wary of these records. In recent years, many accelerograms have been written at large, extensively instrumented structures. Where these instrument packages include free-field sensors, only those records are included. If there is no free- field sensor, the building ground-level or basement instrument recordings are included. Most of the accelerograms were digitized from film or paper records. They came to us in the form of unequally spaced (time, acceleration) pairs, which were linearly interpolated to even time spacing (200 points per second) by using the HIFRIC program of the AGRAM package (Converse, 1984) with the interpolate-only option. We chose this format in the interest of conserving space. In spite of the large storage capacities of CD-ROM's, we needed to minimize the individual file size because of the large number of acceleration records. By using evenly spaced values, we were able to save the space that would have been occupied by the time values. More recently,many of the records were digitally recorded at evenly spaced intervals, some at 100 points per second. In the interest of consistency, these were interpolated to 200 points per second. A few records from the 1962 Acapulco earthquake that we received through Caltech were in the form of evenly spaced data at 10 points per second; we left these records as they were. Each file consists of 80-byte ASCII card-image records. NOTES CONCERNING UNCORRECTED DATA, 1975-79 Since 1975, the U.S. Geological Survey (USGS) has used a commercial digitizing company to digitize film records: LS Associates, located in Santa Clara, Calif. (formerly IOM/Towill). For records processed between 1975 and 1979, a point-removal algorithm was used to shorten the arrays of uncorrected data originally digitized at approximately 600 samples per second, and denser near sharp peaks. The algorithm removed a point if it lay sufficiently close to a straight line between its two surrounding points. The process was repeated for newly adjacent points, so that sections of trace appearing to be straight might actually be defined by only the two end points. Subsequent interpolation at 200 samples per second for this collection has resulted in two obvious features: 1. The straight-line segments mentioned above will be refilled with interpolated points, giving a false implication that these segments were initially truly straight. 2. Sharp local peaks will generally be missed by the 0.005-second step length and will therefore be reduced. 3 We assume that all points removed by this algorithm did not contribute to the digitized version of the record, but the process could have left in place points that were affected by high-frequency noise, thus giving this noise effectively more predominance and affecting the high-frequency spectral content. Because we are dealing with amplitude differences of about 25 microns (25x10E-6 m) on the original film, the total effect is assumed to be negligible. HOW TO CORRECT THE RECORDS The files consist of evenly spaced uncorrected accelerograms, corresponding to Volume 1 of Caltech's Blue Book series. We chose to publish uncorrected records despite the greater interest of the engineering community in corrected data, because the CD-ROM disk is primarily an archive. As discussed earlier, we are storing digital accelerograms in this collection partly to prevent their permanent loss, as well as to facilitate their distribution. The uncorrected records stored here can be corrected by using values that suit each user. Correction procedures basically include bandpass filtering (removing noise contamination) and instrument correction (removing the effects of frequency-dependent instrument response). By publishing the accelerograms in a more pristine condition, we may be inconveniencing some users. However, a user requiring, for whatever reason, a wider band, would not be able to recover the data from a corrected version. If there is sufficient demand, a collection of corrected accelerograms may be published in the future. Software that will process these records on a personal computer (PC) is available from the USGS. The software, currently named BAP (for Basic Accelerogram Processing), will apply linear corrections (subtraction of a best-fit straight line), if necessary, instrument corrections, and filters. It will integrate an acceleration-time series to velocity and displacement, compute Fourier amplitude spectra and response spectra, and plot the results at each step. For information on acquiring the most recent version of the software, send a self-addressed stamped envelope to: Attn: April Converse U.S. Geological Survey, M/S 977 ES&G Data Project (BAP) 345 Middlefield Road Menlo Park, CA 94025-3591 U.S.A. For the user who wishes to correct these records (using BAP or other software), the procedure is discussed in the BAP user's manual (Converse, 1991). In addition, many of the references mentioned in the individual files discuss corrected records and list the filter values used to produce them. The California Strong Motion Instrumentation Program (CSMIP) of the California Department of Conservation's Division of Mines and Geology (CDMG) have asked that their recommended filters for correcting their records be listed in the file headers, (see below). In addition, the comment section of each file contains the following statement: 4 ******************** This is an uncorrected (Volume 1) accelerogram provided by the California Strong Motion Instrumentation Program (CSMIP) of the California Department of Conservation's Division of Mines and Geology. The corrected (Volume 2) accelerogram is available from that agency. However, if the user prefers to apply their own correction procedures, CSMIP recommends, based on digitizing noise analysis, that among other data correction aspects, a bandpass filter with ramps at: " f1 ", " f2 ", " f3 ", " f4 " cycles/sec be used. To help establish the benefit of data collected at State of California expense, please send a reprint of any publication using this accelerogram to: California Department of Conservation Division of Mines and Geology 630 Bercut Drive Sacramento, California 95814 Attn: Data Utilization ************************** We urge the reader to follow the CDMG's wishes. A NOTE ON "COMPONENT DIRECTIONS" ON USGS ANALOG FILM RECORDS In 1978, two changes were made to the way "component directions" were listed in USGS, and earlier, reports containing information on original strong-motion records. Before the Santa Barbara earthquake of August 13, 1978, the component direction was listed as "pendulum motion," that is, the direction in which the transducer mass and its mirror were displaced by the technician to make the trace to move in the positive direction (upward on the film). Previously, the direction was written in quadrant form, for the direction of "ground" or "instrument" or "case" acceleration the causes a positive trace direction on the film. This direction is 180 degrees different from that in the previous convention. At the same time, the method of direction notation was changed to azimuthal (degrees clockwise from North). Our previous example of S50W would be rotated 180 degrees to N50E and would be written as 50 degrees. Caltech made an independent effort during 1968 to 1975 to standardize component directions in its reports (the Caltech reports listed directions in both quadrant and azimuthal format). The choice of component direction is the same as the USGS post-1978 convention: "ground" or "case." Many errors have since been found or suspected, particularly in those accelerograms recorded from 1933 through 1968. The user is cautioned when using these records if he or she needs specific positive or negative directions for his or her investigations. 5 THE HEADER INFORMATION Each file contains a header section before the set of evenly spaced acceleration values. The header is designed to provide the user with information about the earthquake and the recording instrument (see appendix B for a more complete description of the file format). It includes a few lines of prose designed to identify quickly the earthquake and recording station, followed by 48 integer variables and 50 real variables. Both the integer and real headers contain several slots as yet undefined; these slots were included so that more information can be added to future records without changing the format. In addition to the headers, is a variable number of comment lines (the number of comments is indicated as the 16th integer value) that can contain additional information about the earthquake or the record. For example, in the case of the CSMIP records, they contain the correction parameters described above. The 18th integer value is a mistake flag. Most of the time it is set to zero, but if there is a problem with the record, such as spikes or unusual noise, it is set to 1, in which case, additional information will be found in the comment section of the file header. We recommend that programs written to use these files should identify records with I18 = 1 and bring them to the user's attention. The comments usually list one or more references that describe the earthquake, station, or some other aspect of the record. The earthquake locations and magnitudes were taken from these references. It is not uncommon for more than one agency to collect digitized accelerograms and provide references. This overlap can result, for example, in the header information for different agency recordings of the same earthquake containing different source locations or magnitudes. In the same vein, for some accelerograms written on temporary instruments at Mammoth, Calif., the magnitude listed is less than 5. According to our criteria, these accelerograms should not have been included, but if any agency recording an earthquake determined its magnitude as 5 or larger, we included all of the accelerograms it wrote from all agency networks. Another type of possibly mismatched information occurs in the headers of the Universidad Nacional Autonoma de Mexico (UNAM) accelerograms: The earthquake locations are from the USGS' Earthquake Data Base System, but the distances are from the headers of the original UNAM files. Differences might exist between these distances and any that the user might calculate using the earthquake and station locations contained in the headers. We did not have the time and resources to do a thorough literature search for every piece of information in each of the station recordings. In some cases, the reference cited was preliminary and may be superseded by later work. The information contained in the headers is useful as a guideline and commonly is the best available, but we recommend that those who want a high degree of accuracy in the epicentral distance, epicenter location, and (or) earthquake magnitude check that the reference(s) listed meet their specifications. 6 PECULIARITIES IN THE DATA FILES As might be expected in any collection this large, there are a few quirks in the data. We suggest that the user be aware of the following: Caltech's Blue Book series files list time in Pacific standard or daylight time (P.s.t. or P.d.t.)(the rest of the records are in universal time coordinated [U.t.c.]). We left these as they were, but wrote "PST" next to the time. Also in the Blue Book series records, we substituted the magnitudes and distances from Joyner and Boore (1981) wherever possible. The CDMG's Mammoth Lakes instrument parameters (frequency and damping) were contained in the original computer file headers and do not always agree with the reference cited. The null (no entry) value is usually -32768 for integers and 3.0E-38 for real numbers. Occasionally, the reformatting program picked up other values contained in the input files. Therefore, we recommend that programs read the null value from each file instead of assuming the values listed above. A similar warning is necessary for the sampling rate: Most of the records have a sampling rate of 200 points per second, but, as mentioned earlier, the 1962 records from Acapulco were provided to us through Caltech with a sampling rate of 10 points per second. We recommend that any software used with these records read the sampling rate instead of assuming that it will be 200 points per second. Some records list the horizontal orientation for vertical records as 0 instead of the null value. This is because it was listed that way in the original record. The value of ML listed in the digital Guerrero array (University of Nevada at Reno, [UNR]/UNAM) is really M-II, the magnitude given in the SISMEX bulletin, based on coda duration. The number of points in some records is greater than 32678, a value that can cause problems in user programs if it exceeds the maximum value that can be used as an integer. FILE NAMES We wished the file names to describe the contents. Because we are limited to 12 characters (at least on PC's), we came up with the following somewhat-unwieldy convention. The files from each year are stored in a separate directory (named by year). Characters 1-3 are the day of the year (001-366); character 4 is a letter corresponding to the hour (A=0,...X=23); characters 5-6 are the minutes; characters 7-11, are the four-character station name, unfortunately split by a period in character 9; and character 12 is the component code. For example, a recording of the third component of station STNA from an earthquake occurring on July 20 (J.d. 201), 1979 at 10:22 U.t.c. would be in the directory 1979 in a file called 201K22ST.NAC. 7 THE STATION CODES The four-character station codes were taken, wherever possible, from Switzer and others (1981) or from the agency which provided the records. Generally they are only three characters long, in which case the fourth character is a zero. When two earthquakes occurred within the same minute, we used 1 as the fourth character. For some records, no station code was listed in the literature; in this case, we made up a four character code with X as the first character, although not all station codes beginning with X are our invention. THE DATA-BASE INDEX FILES We have included a set of five files containing a brief description of each accelerogram. These files were designed to be used as input to a data base, so that the user can select records of interest. For each accelerogram they include the earthquake name, station name, component, date, time, maximum and minimum acceleration, earthquake location and magnitude, station location and epicentral distance. This information was taken from the headers of the data files and is subject to the same warnings about accuracy. The format of these files is listed in appendix C. PRIMARY SOURCES OF DATA Most of the early data (1933-71) were published in the Blue Book Series (California Institute of Technology 1969-74). These accelerograms were collected by the predecessors of the USGS' National Cooperative Strong-Motion Instrument Network, and processed by the Caltech's Earthquake Engineering Research Laboratory. Caltech also provided several records obtained after the Blue Book series was published (the 1971 San Fernando earthquake was the last earthquake it contained) and a few that were omitted. The UNAM's Instituto de Ingenieria provided us with their sizable (>400 station recordings) collection of digital records from various locations in Mexico (Anderson and Mena, 1987). John Anderson of the Seismology Laboratory, Mackay School of Mines, UNR, gave us copies of the records collected from the Guerrero digital array in Mexico, which UNAM/University of California, San Diego (UCSD), and UNAM/UNR have been operating since 1985 (Anderson and others, 1987a, 1987b). After the 1971 San Fernando earthquake, records from the national network operated by the USGS have been processed by the USGS, described in a series of USGS Open-File Reports, and disseminated by the National Geophysical Data Center, National Oceanic and Atmospheric Administration (NOAA), in Boulder, Colo. The California Strong Motion Instrumentation Program provided us with accelerograms from their California array and from the 1986 San Salvador earthquake. Lamont-Doherty Geological Observatory of Columbia University also maintains the NCEER's Strong-Motion Data Base (Friberg and Jacob, 1990). The U.S. Army Corps of Engineers has collected records from dams in New Hampshire and Idaho (Chang, 1985, 1987). Robert Herrmann of Saint Louis University (SLU) provided accelerograms from the New Madrid, Mo., area. 8 Canadian records are from the Geological Survey of Canada (Weichert and others, 1982, 1986). Southern California Edison sent us several records from their instruments at several sites in southern California and the Sierra Nevada. Kinemetrics, Inc., furnished us with accelerograms from the 1984 Morgan Hill, Calif., earthquake written at facilities owned by IBM Corp. and maintained by Kinemetrics. The record from the 1986 Painesville, Ohio, main shock was written at the Perry Nuclear Power Plant, owned by the Cleveland Electric Co. Much of our information about earthquakes and accelerograms came from previous catalogs, as described in detail by Seekins and others (1989). ACKNOWLEDGMENTS This collection would not exist without the help of the following individuals. Tom Hanks has always been the driving force behind this project. Inspired by the storage capability of CD-ROMs, it was his idea to assemble and distribute this data set on what was, at the time, a relatively new medium. April Converse wrote the BAP software that is available to process the data in this collection; she also wrote the AGRAM software that we used to process most of the files. She has often helped us with her programming knowledge and advice; we appreciate her attention to potential problems in the data set and, most importantly, her good spirit, patience, and constant encouragement. Larry Baker was invaluable in helping us to read magnetic tapes from antiquated computers. His understanding of computer systems was a valuable resource throughout the lifetime of this project; he has always been generous with his time and ideas. Howard Bundock also came to our assistance several times during computer crises. Chuck Mueller supervised the project and provided thoughtful guidance. Bill Joyner had already accumulated a large data subset on magnetic tape and was helpful in finding several records; he also provided information and ideas that were helpful in shaping the catalog as a whole. Pete Mork patiently searched old tapes written by former employees to find obscure records for us. Jo Switzer maintains an excellent data base of information about the recording stations; it was an important resource. Dave Boore helped us check the accuracy of the index files. Tom Holzer facilitated data collection and publication. Carl Abston of the USGS Office of Scientific Publications in Denver, Colo., helped us with the nuts and bolts of writing the files onto CD-ROM. In addition to providing us with data from the Guerrero digital array, John Anderson of UNR's Mackay School of Mines, acted as an intermediary between the USGS and UNAM, arranging for the release of their data and transporting magnetic tapes. He has been supportive of this effort and was generous with his time and guidance, as well as with his data; we have benefited greatly from his interest and assistance. UNAM's Instituto de Ingenieria went to a great deal of trouble to make copies of their data for us; we are grateful that they provided us with their records and gave us permission to publish them. 9 Jim Beck of Caltech helped us to locate post-Blue Book series records. Ahmed Abdel-Ghaffar of the University of Southern California made a valiant, albeit-unsuccessful effort to find the lost records from the 1976 Whittier, Calif., earthquake. George Segal of Kinemetrics Inc., and Frank Stead and Mike White of the Cleveland Electric Co. arranged permission for us to use the Perry Nuclear Power Plant record written by the January 1986 Cleveland, Ohio earthquake. Charles Kircher of Jack Benjamin and Associates and Dale Parker of IBM Corp. arranged permission for us to use IBM's Morgan Hill records. Paul Friberg helped us to use the NCEER data base and provided us with Lamont-Doherty-processed Alaska records. Dennis Ostrom of Southern California Edison sent us copies of their records and information about them. REFERENCES Anderson, J.G., R. Quaas, D. Almora M., J. Manuel Velasco, E. Guevara O., L.E. de Pavia R., A. Gutierrez R., and R. Vazquez L., 1987a, Guerrero, Mexico Accelerograph Array: Summary of Data Collected in the Year 1985: Guerrero Array Team, Instituto de Ingenieria - UNAM and Seismological Laboratory, UNR Report GAA-2. Anderson, J.G., R. Quaas, D. Almora M., J. Manuel Velasco, E. Guevara O., L. E. de Pavia R., A Gutierrez R., R. Vazquez L., 1987b, Guerrero, Mexico Accelerograph Array: Summary of Data Collected in the Year 1986: Guerrero Array Team, Instituto de Ingenieria - UNAM and Seismological Laboratory, UNR Report GAA-3. California Institute of Technology, 1969-74, Strong Motion Earthquake Accelerograms - Uncorrected Accelerograms, Earthquake Engineering Laboratory; Pasadena. Chang, F.K., 1985, Analysis of Strong-Motion Data From the Mount Borah, Idaho, Earthquake of 28 October 1983: U.S. Army Corps of Engineers, Waterways Experiment Station, Miscellaneous Paper GL-85-12. Chang, F.K., 1987, Response Spectral Analysis of Franklin Falls Dam, New Hampshire: U.S. Army Corps of Engineers Miscellaneous Paper GL-87-1. Converse, April, 1984, AGRAM: A Series of Computer Programs for Processing Digitized Strong-Motion Accelerograms, Version 2.0: U.S. Geological Survey Open-File Report 84-525. Converse, April, 1991, BAP: Basic Strong-Motion Accelerogram Processing Software, Version 1; in press. Friberg, P.A. and K.H. Jacob, 1990, NCEER Strong-Motion Data Base: A User Manual for the GeoBase Release (Version 1.0 for the SUN3). NCEER Technical Report NCEER-90-0005. 10 Joyner, William B., and David M. Boore, 1981, Peak Horizontal Acceleration and Velocity from Strong-Motion Records Including Records from the 1979 Imperial Valley, California Earthquake. Bull. Seis. Soc. Am., Vol. 71, no.6, p. 2011-2038. Seekins, Linda C., A. Gerald Brady, and Charles S. Mueller, 1989, Digitized Strong-Motion Accelerograms of North America Through 1986: U.S. Geological Survey Open-File Report 89-93, 37 p. Switzer, J., D. Johnson, R. Maley, and R. Matthiesen, 1981, Western Hemisphere Strong-Motion Accelerograph Station List - 1980; U.S. Geological Survey Open-File Report 81-664. Weichert, D.H., P.W. Pomeroy, P.S. Munro, and P.N. Mork, 1982, Strong Motion Records from Miramichi, New Brunswick, 1982 Aftershocks: Pacific GeoScience Centre, Earth Physics Branch Open File Report 82-31. Weichert, D.H., R.J. Wetmiller, R.B. Horner, P.S. Munro, and P.N. Mork, 1986, Strong Motion Records from the 23 December 1985, Ms 6.9 Nahanni, NWT, and some Associated Earthquakes. Geological Survey of Canada, Pacific Geoscience Centre, Open File Report 86-1-PGC, 9 p. APPENDIX A - REFERENCES CITED IN THE DATA FILES Anderson, John G., and Richard S. Simons, 1982, Mexicali Valley Accelerogram Data: 1978-1980: Institute of Geophysics and Planetary Physics, Strong Motion Project Report 82-1, UCSD, 5 p. Anderson, J.G., R. Quaas, D. Almora M., J. Manuel Velasco, E. Guevara O., L.E. de Pavia R., A. Gutierrez R., and R. Vazquez L., 1987, Guerrero, Mexico Accelerograph Array: Summary of Data Collected in the Year 1985: Guerrero Array Team, Instituto de Ingenieria - UNAM and Seismological Laboratory, UNR Report GAA-2. Anderson, J.G., R. Quaas, D. Almora M., J. Manuel Velasco, E. Guevara O., L.E. de Pavia R., A. Gutierrez R., and R. Vazquez L., 1987, Guerrero, Mexico Accelerograph Array: Summary of Data Collected in the Year 1986: Guerrero Array Team, Instituto de Ingenieria - UNAM and Seismological Laboratory, UNR Report GAA-3. Anderson, J.G. and J.N. Brune, 1991, The Victoria Accelerogram for the 1990 Mexicali Valley Earthquake; Earthquake Spectra, in press. Beaven, J., and K.H. Jacob, 1984, Processed Strong-Motion Data from Subduction Zones: Alaska; Report 1 in the Series 'Lamont-Processed Strong Motion Data', Lamont-Doherty Geological Observatory. Brady, A.G., E.C. Etheridge, R.P. Maley, P.N. Mork, B.L. Silverstein, D.A. Johnson, A.V. Acosta, R.D. Forshee, and M.J. Salsman, 1986, Preliminary Report on Records from the USGS-Maintained Strong-Motion Network in the Hollister Area January 26, 1986. USGS Open-File Report 86-156. 11 Brady, A.G., and V. Perez, Strong-Motion Earthquake Accelerograms Digitization and Analysis, USGS Seismic Engineering Data Report, 1972 Records. USGS Open-File Report 78-941, 1978. Brady, A.G., and V. Perez, 1983, Processed Accelerograms from Coyote Dam: USGS Open-File Report 83-166, 82 p. Brady, A.G., and V. Perez, 1979, Strong-Motion Earthquake Accelerograms Digitization and Analysis, USGS Seismic Engineering Data Report 1974-1975 Records. USGS Open-File Report 79-929. Brady, A.G., R.L. Porcella, G.N. Bycroft, E.C. Etheredge, P.N. Mork, B. Silverstein, and A.F. Shakal, 1987, Processing of Strong-Motion Recordings from the Main Shock; in The Morgan Hill, California Earthquake of April 24, 1984. USGS Bulletin 1639, S.N. Hoose, ed., p. 53-60. Brady, A.G., R.L. Porcella, G.N. Bycroft, E.C. Etheredge, P.N. Mork, B. Silverstein, and A.F. Shakal, 1987, Computer plots of Strong-Motion Results from the Main Shock; in The Morgan Hill, California Earthquake of April 24, 1984. USGS Bulletin 1639, S.N. Hoose, ed., p. 139-256. Brune, J.N., F.L. Vernon III, R.S. Simons, J. Prince, and E. Mena, 1982, Strong-Motion Data Recorded in Mexico During the Main Shock; in The Imperial Valley, California, Earthquake of October 15, 1979, USGS Prof Paper 1254, pp 319-350. California Institute of Technology, 1969-74, "Bluebook" series - Volume 1: Strong Motion Earthquake Accelerograms - Uncorrected Accelerograms, Earthquake Engineering Laboratory, Pasadena. CDMG, 1978, Compilation of Strong-Motion Records Recovered from the Santa Barbara Earthquake of 13 August 1978. California Division of Mines and Geology Preliminary Report 22, 43 p. CDMG, 1985, Selected Accelerograms from the Redlands, California Earthquake of October 2, 1985 (Including First Records from a Base-Isolated Building). CDMG Preliminary Data Report OSMS 85-02, 17 p. Chang, F.K., 1985, Analysis of Strong-Motion Data From the Mount Borah, Idaho, Earthquake of 28 October 1983; U.S. Army Corps of Engineers, Waterways Experiment Station, Miscellaneous Paper GL-85-12. Chang, F.K., 1987, Response Spectral Analysis of Franklin Falls Dam, New Hampshire. U.S. Army Corps of Engineers Miscellaneous Paper GL-87-1. Friberg, P.A., and K.H. Jacob, 1989, Processed Strong Ground Motion Data From Alaska: First Update, Through June 1987. Report 2 in the Series 'Lamont Processed Strong Motion Data': Columbia University, Lamont-Doherty Geological Observatory. 12 Haar, L.C., J.B. Fletcher, and C.S. Mueller, 1984, The 1982 Enola, Arkansas, Swarm and Scaling of Ground Motion in the Eastern United States. Bull. Seis. Soc. Am., v. 74, no. 6, p. 2463-2482. Hartzell, S.H., and Brune, J.N., 1979, The Horse Canyon Earthquake of August 2, 1975 - Two Stage Stress-Release Process in a Strike-Slip Earthquake. Bull. Seis. Soc. Am., v. 69, p. 1161-1173. Hermann, R. B., 1977, Analysis of Strong Motion Data from the New Madrid Seismic Zone: 1975-1976. Saint Louis University Department of Earth and Atmospheric Sciences Publication 239, 144 p. Huang, M.J., D.L. Parke, R.W. Sherburne and A.F. Shakal, 1987, Processed Strong Motion Data from the Palm Springs Earthquake of 8 July 1986: Part 1. Ground-Response Records. California Strong Motion Instrumentation Program, Report # OSMS 87-01. CDMG. Jennings, Paul C., 1962, Velocity Spectra of the Mexican Earthquakes of 11 May and 19 May 1962: California Institute of Technology, Earthquake Engineering Research Laboratory, 18 p. Joyner, William B., and David M. Boore, 1981, Peak Horizontal Acceleration and Velocity from Strong-Motion Records Including Records from the 1979 Imperial Valley, California Earthquake. Bull. Seis. Soc. Am., vol. 71, no. 6, p. 2011-2038. Kinemetrics, 1982, Data Report: Santa Barbara Earthquake August 13 1978. Kinemetrics, 1984, Morgan Hill Earthquake, April 24 1984, Strong-Motion Data from the IBM Digital Accelerograph Network; San Jose and Almaden Facilities; for IBM Corporation. Lee, V.W. and M.D. Trifunac, 1987, Strong Earthquake Ground Motion Data in EQINFOS: Part 1; University of Southern California, Department of Civil Engineering Report 87-01. Maley, R.P and E.C. Etheridge, 1981, Strong-Motion Data from the Westmoreland, California Earthquake of April 26, 1981; USGS Open-File Report 81-1149. Maley, R.P., E.C. Etheredge, and A. Acosta, 1986, U.S. Geological Survey Strong-Motion Records from the Chalfant Valley, California, Earthquake of July 21, 1986, USGS Open File Report 86-568, 19 p. Miller, R.K., and S.F. Felszeghy, 1978, Engineering Features of the Santa Barbara Earthquake of August 13, 1978; Dept of Mechanical and Environmental Eng., UCSB; UCSB-ME-78-2; published by Earthquake Engineering Research Institute. Mork, P.N., and A.G. Brady, 1981, Processed Accelerogram From Monticello Dam, Jenkinsville, South Carolina, 16 October 1979, 0706 UTC: USGS Open-File Report 81-1214. 13 Mueller, C., P. Spudich, E. Cranswick, and R. Archuleta, 1981, Preliminary Analysis of Digital Seismograms from the Mammoth Lakes, California Earthquake Sequence of May-June, 1980. USGS Open-File Report 81-155. Porcella, R.L., R.B. Matthiesen, R.D. McJunkin and J.T. Ragsdale, 1979, Compilation of Strong-Motion Records from the August 6, 1979 Coyote Lake Earthquake: CDMG Preliminary Report 25; USGS Open-File Report 79-385. Porcella, R.L., R.B. Matthiesen, and R.P. Maley, 1982, Strong-Motion Data Recorded in the United States, in The Imperial Valley, California, Earthquake of October 15, 1979: USGS Professional Paper 1254, p. 289-318. Porcella, R., E. Etheredge, R. Maley, J. Switzer, 1987, Strong-Motion Data from the July 8, 1986 North Palm Springs Earthquake and Aftershocks: USGS Open-File Report 87-155. L.D. 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USGS Open-File Report 86-331. 15 APPENDIX B - DATA-FILE FORMAT * * XXXXA date time(GMT) earthquake name M= Ms= Ml= station= component= epicentral dist= pk accel= instrument type= data source= * * * (note: XXXXA represents the five-character station-component code used in the file name) INTEGER VARIABLES (8I10) variable AGRAM/ESG number description cross-ref ________ ______________________ __________ 1 integer null value 3 2 year (4 digits) first sample time 10 3 day of year " " " 11 4 hour " " " 12 5 minute " " " 13 6 second " " " 14 7 millisecond " " " 15 8 recorder serial number 20 9 recorder channel number:this file 28(ESG) 10 recorder channel number:total 29(ESG) 11 number of channels recorded for 30 this station 12 sensor serial number 40(ESG) 13 vertical orientation (degrees 41 from up) 0< I13 <180 14 horizontal orientation (degrees 42 east of north) 0< I14 < 360 15 sensor type code 43(ESG) 2 Sprengnether SA-3000 3-component fba 30 Kinemetrics FBA-13 3-component fba 31 Kinemetrics FBA-11 1-component fba 101 SMA-1 102 C&GS Standard 103 AR-240 104 RFT-250 16 105 RFT-350 106 MO-2 107 RMT-280 108 SMA-2/3 109 DSA-1/DSA-3 110 DCA-300 111 DCA-333 112 A-700 113 SSA-1 114 CRA-1 115 MO-2 116 FBA-3 117 SMA-2 118 DCA-310 119 FBA-13 16 number of comment cards following the header information 17 number of acceleration values 18 mistake flag - I18=1 means that there is some sort of mistake in the file - read the comments before using the record. Integer parameters 19-29 are for future structural collections; they are not used in any of the files in the current collection. 19 Type of structure 1 building 2 bridge 3 dam 4 other null not a structure 20 Structure number corresponding to printed information 21 Transducer number of recording system as shown on the drawing 22 Total number of transducer channels for this structure The following integer parameters are for buildings (1 in integer variable 18): 23 Number of floors above grade including the roof 24 Number of stories below grade 25 Floor on which this sensor is located -1 1st subbasement, etc. 0 basement 1 grade level 2+ floor levels above grade 17 The following are for bridges 26 Number of spans 27 Location of transducer 0 free field 1 at the base of a pier or abutment 2 on an abutment 3 on the deck at the top of a pier 4 on the deck between piers or between an abutment and a pier The following are for dams: 28 Location of this transducer 0 upstream or downstream free field 1 at the base of the dam 2 on the crest of the dam 3 on the abutment of the dam 29 Type of construction 1 Reinforced-concrete gravity 2 Reinforced-concrete arch 3 earth fill 4 other 30-48 Undefined REAL VARIABLES(5E15.7) variable AGRAM/ESG number description cross-ref _________ _____________ ____________ 1 real null value 2 2 sample rate (samples/s) 5 3 earthquake latitude (dec. deg.) 10 (ESG) 4 earthquake longitude (dec. deg.) 12 (ESG) 5 earthquake depth (km ref. s.l.) 14 6 source magnitude M (moment 15 magnitude) 7 " " Ms 8 " " ML 9 " " M (other) 10 seismic moment (dyne-cm) 16 11 station latitude (dec. deg.) 40 (ESG) 12 station longitude (dec. deg.) 42 (ESG) 13 station elevation (m ref. s.l.) 44 14 station offset N (m) 15 station offset E (m) 16 station offset up (m) 17 epicentral distance (km) 19 18 epicenter to station azimuth 20 (degrees east of north) 0.0 < R17 <360.0 18 19 digitizing constant (counts/V) 46 for DR100 data, digitization units (units/cm) for SMA data 20 antialias-filter corner frequency 47 (hz) 21 antialias-filter poles (rolloff= 48(ESG) 6dB/octave per pole) 22 natural frequency of the sensor 49 (hz) 23 sensor damping coefficient 50 (fraction of critical) 24 coil constant(V s**2/cm) 51 for DR100 or recorder sensitivity (cm/g) for SMA data 25 amplifier gain (dB) for a DR100 52 26 pre-amp gain (dB) for a DR100 53 27 high-pass filter - suggested corner frequency (default = reciprocal of two times the strong motion duration 28 low-pass filter - suggested corner frequency (natural frequency of the accelerometer) 29 time of the maximum value (s) 30 value of the maximum value (cm/s**2) 31 time of the minimum value (s) 32 value of the minimum value (cm/s**2) 33-36 F1-F4 - recommended filters for cor- recting CDMG records 37-50 undefined ! comment cards go here Acceleration values 8 (pe10.4e1) APPENDIX C - INDEX-FILE FORMAT Station and component code, Earthquake name, Station name, Component (a5,1x,2a30,a10) Year, Julian Day, Hour, Minute, Maximum Acceleration, Minimum Acceleration (4i10,2e15.7) Earthquake Latitude, Earthquake Longitude, Earthquake Depth, Station Latitude, Station Longitude (5e15.7) Moment Magnitude, Ms, ML, M(other), Epicentral Distance (5e15.7) 19