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



                             TECHNICAL INFORMATION


     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 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. Porter, 1982, Data-Processing Procedures for Main-Shock
     Motions Recorded by the California Division of Mines and Geology
     Strong-Motion Network; in The Imperial Valley, California,
     Earthquake of October 15, 1979:  USGS Professional Paper 1254, p.
     407-432. 
     
     Seale, S.A. and R.J. Archuleta, 1988, Site Effect at McGee Creek,
     California; in Earthquake Engineering and Soil Dynamics II - Recent
     Advances in Ground-Motion Evaluation.  ASCE Geotechnical Special
     Publication 20, J.L. Von Thun, ed., p. 173-187.                   
     
     Seekins, L.C., and T.C. Hanks, 1978, Strong-Motion Accelerograms of
     the Oroville Aftershocks and Peak Acceleration Data.  Bull. Seis.
     Soc. Am., v. 68, no. 3, p. 677-689.                 
     
     Shakal, A.F. and J.T. Ragsdale, 1983, Strong-Motion Data From the
     Coalinga, California Earthquake and Aftershocks; in The 1983
     Coalinga, California Earthquakes, J.H. Bennett and R.W. Sherburne,
     eds.,  CDMG Special Publication 66, p. 321-335.                   
     
     Shakal, A.F., M.J. Huang, D.L. Parke, and R. Linares, 1986,
     Processed Strong Motion Data from the San Salvador Earthquake of
     October 10, 1986. CDMG Report OSMS 86-07, 113 p.            
     
     Shakal, A.F., M.J. Huang, D.L. Parke, and R.W. Sherburne, 1986,
     Processed Data from the Strong-Motion Records of the Morgan Hill
     Earthquake of 24 April 1984, Part 1, Ground-Response Records.  CDMG
     California Strong Motion Instrumentation Program Report OSMS 85-04,
     249 p.
    
     Spudich, P., E. Cranswick, J. Fletcher, E. Harp, C. Mueller, R.
     Navarro, J. Sarmiento, J. Vinton, and R. Warrick, 1981, Acquisition
     of Digital Seismograms During the Mammoth Lakes, California,
     Earthquake Sequence of May-June 1980.  USGS Open-File Report 81-38. 



                                     14


    
     Turpen C.D., 1980, Preliminary Report:  Strong-Motion Records from
     the Mammoth Lakes, California Earthquakes of May, 1980.  CDMG
     Office of Strong-Motion Studies.                            
                                         
     USGS, 1974, Seismic Engineering Program Report, October-December
     1974, USGS Geological Circular 713.                          
           
     USGS, 1976,  Seismic Engineering Data Report, Strong-Motion
     Earthquake Accelerograms, Digitization and Analysis, 1971 Records. 
     Open-File Report 76-609. 
     
     USGS, 1976, Seismic Engineering Program Report,  October-December
     1975.  Circular 717-D.          
                                                       
     USGS, 1976, Seismic Engineering Program Report, July-September
     1975.  Circular 717-C.          
     
     USGS, 1989, Earthquake Data Base System, Branch of Global
     Seismology and Geomagnetism On-Line Information Program.  Golden,
     Colo.
     
     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. 
     
     Wesson, R.L. and C. Nicholson, eds., 1986, Studies of the January
     31, 1986  Northeastern Ohio Earthquake; A Report to the U.S.
     Nuclear Regulatory Commission.  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