Engineering Institute, National Autonomous Engineering Institute, National Autonomous University of Mexico (UNAM)University of Mexico (UNAM)

RECORD PROCESSING METHODS RECORD PROCESSING METHODS AND PROCEDURES FOR THE AND PROCEDURES FOR THE MEXICAN STRONG MOTION MEXICAN STRONG MOTION

PROGRAMPROGRAM

Leonardo Leonardo Alcántara NAlcántara NCitlali Pérez YCitlali Pérez Y

Main seismic events in MexicoMain seismic events in Mexico

Distribution of the Mexican Accelerographic NetworkDistribution of the Mexican Accelerographic Network

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Station 2 25 80 150 269 547 650

Accelerogram 0 22 118 669 2546 13835 22350

1960 1970 1975 1985 1990 1999 2004

Accelerographs and records gotten in MEXANET from 1960 to 2004Accelerographs and records gotten in MEXANET from 1960 to 2004

Architecture of the Mexican Strong Motion DatabaseArchitecture of the Mexican Strong Motion Database

Structure of the ASCII Standard Acceleration FileStructure of the ASCII Standard Acceleration File

Compact Disk vol 2 to search Mexican accelerograms from 1960 to 1999Compact Disk vol 2 to search Mexican accelerograms from 1960 to 1999

First stage on seismic data processingFirst stage on seismic data processing

Standard ProcessingStandard Processing

• Offset correction.Offset correction. In order to eliminate the static acceleration to the signal.

• Search for GPA.Search for GPA. Most of the programs give the values of peak accelerations although they are not always in gal units.

• Glitches clean up.Glitches clean up. This activity specially applies to the data retrieved from magnetic tapes. A more advanced tools applies a pass-band filter to eliminate spurious spikes or electric noise signals.

• Identification of the seismic event that Identification of the seismic event that triggered the stationtriggered the station.. Consulting the epicenter location catalogs issued by the Mexican Seismological Service.

• Time drift adjustments.Time drift adjustments. Time corrections require different procedures for different instruments, so special routines are used to correct time and to associate date .

• ASCII Standard Format conversionASCII Standard Format conversion.. Data generated are transmitted as binary files and then they are transformed into temporary ASCII files in very different types of formats. Some differences are:

Acceleration series are stored in different formats

Information header varies and sometimes is not provided.

Acceleration values can be specified in counts, gals, fraction of G or volts.

Pre-process stage to get the Mexican Standard ASCII filesPre-process stage to get the Mexican Standard ASCII files

   Col                           Col                             Col  1. 1*************************************40*************************************80   2.                       INSTITUTO DE INGENIERIA, UNAM   3.                 Coordinacion de Instrumentacion Sismica   4.            Ciudad Universitaria, Apartado Postal 70-472, Mexico, D.F.   5. Tel. (525)5622-3412, Fax. (525)5616-1514, e-mail: isismica@pumas.iingen.unam.mx   6. ********************************************************************************   7. MEXICAN STANDARD ACCELERATION FILE   8. FORMAT VERSION                         : 2.0   9. FILE NAME                              : COPL9509.141  10. DATE AND TIME OF CREATION              : September 25, 1995/14:38:13  11. REF. ACCELERATION CATALOG, SMIS 1995   : NUM. REG. 1355/PAG. 146  12.  13.  14. ================================================================================  15. INFORMATION ABOUT THE STATION  16. STATION NAME                           : COPALA  17. STATION CODE                           : COPL  18. LOCATION OF THE STATION                : Federal Elementary School  19.                                        : "Otilio Montano"  20.                                        : Copala, Guerrero  21.                                        :  22.                                        :  23. GEOGRAPHIC COORDINATES OF THE STATION  : 16.605 LAT. N  24.                                        : 98.974 LONG. W  25. ALTITUDE (meters)                      : 40  26. SOIL TYPE                              : Weathered Granite Gneiss  27.                                        :  28.                                        :  29. INSTITUTION IN CHARGE OF ITS OPERATION : Instituto de Ingeniería, UNAM  30.                                        : Coordinacion de Instrumentacion Sismica  31.  32. ================================================================================  33. INFORMATION ABOUT THE ACCELEROGRAPH  34. ACCELEROGRAPH MODEL                    : DCA-333  35. SERIAL NUMBER                          : 201  36. NUMBER OF CHANNELS                     : 3  37. ORIENTATION C1-C6 (bearing;orientation): /V/N90E/N00E  38. ORIENTATION C7-C12 (bear.;orientation) :  39. SAMPLING SPEED, C1-C6 (samples/sec)    : /100/100/100  40. SAMPLING SPEED, C7-C12 (samples/sec)   :  41. SENSORS FULL SCALE, C1-C6, (g)         : /2/2/2  42. SENSORS FULL SCALE, C7-C12, (g)        :  43. SENSORS NAT. FREQUENCY C1-C6, (Hz)     : /30.0/30.0/30.0  44. SENSORS NAT. FREQUENCY, C7-C12, (Hz)   :  45. SENSORS DAMPING, C1-C6                 : /0.71/0.72/0.78  46. SENSORS DAMPING, C7-C12                :  47. SAMPLING INTERVAL, C1-C6, (sec)        : /0.01/0.01/0.01  48. SAMPLING INTERVAL, C7-C12, (sec)       :  49. TRIGGER THRESHOLD C1-C6, (Gal)         : /3/3/3  50. TRIGGER THRESHOLD, C7-C12, (Gal)       :  51. PRE-EVENT MEMORY (sec)                 : 3.62  52. POST-EVENT MEMORY (sec)                : 15  53.  54.  55. ================================================================================  56. INFORMATION ABOUT THE EARTHQUAKE  57. DATE OF THE EARTHQUAKE (GMT)           : September 14, 1995  58. EPICENTRAL TIME (GMT)                  : 14:04:31  59. MAGNITUDE(S)                           : /Mb=6.5/Ms=7.2/Mw=7.4  60. EPICENTER LOCATION                     : 16.830 LAT. N  61.                                        : 98.647 LONG. W  62. FOCAL DEPTH (km)                       : 21  63. INFORMATION SOURCE                     : Instituto de Geofisica, UNAM  64.                                        : Servicio Sismologico Nacional  65.  66. ================================================================================

 67. INFORMATION ABOUT THIS RECORD  68. TIME OF THE FIRST SAMPLE (GMT)         : 14:04:32.25  69. RECORDING TIME PRECISION (sec)         : 0.01  70. RECORD DURATION (sec), C1-C6           : /63.15/63.15/63.15  71. RECORD DURATION (sec), C7-C12          :  72. TOTAL No. OF SAMPLES, C1-C6            : /6315/6315/6315  73. TOTAL No. OF SAMPLES, C7-C12           :  74. PEAK ACCELERATION (Gal), C1-C6         : /46.42/68.91/77.04  75. PEAK ACCELERATION,C1-C6, AT SAMPLE No. : /1246/1326/1223  76. PEAK ACCELERATION (Gal), C7-C12        :  77. PEAK ACCELERATION,C7-C12, AT SAMPLE No.:  78. UNITS OF THE DATA                      : Gal (cm/sec/sec)  79. DECIMATION FACTOR                      : 1  80. DATA FORMAT (FORTRAN,10 fields/sample) : 3F10.2  81.  82.  83. ================================================================================  84. QUALITY OF THE ACCELEROGRAM  85. Complete digital record with correct absolute time.  86.  87.  88. ================================================================================  89. COMMENTS:  90. This earthquake produced significant damage in the epicentral area. The most  91. affected towns were San Luis Acatlan, Axoyu, Igualapa, and Ometepec on the Costa  92. Chica. 200 houses were severely damaged. About 50 injuries were reported.  93. The earthquake was also strongly felt in Mexico City but produced little damage.  94.  95.  96.  97.  98.  99. 100. 101. 102. 103 104. ================================================================================ 105.   ACCELERATION DATA: 106. ---------+---------+---------+---------+---------+---------+---------+---------+ 107.  CHANNEL-1 CHANNEL-2 CHANNEL-3 CHANNEL-4 CHANNEL-5 CHANNEL-6 CHANNEL-7 CHANNEL-8 108.          V      N90E      N00E 109. ---------+---------+---------+---------+---------+---------+---------+---------+ 110.       0.06      0.04      0.03 111.       0.06      0.04      0.03 112.      -0.42     -0.44      0.03

Mexican Standard Acceleration File, Mexican Standard Acceleration File, ASA v 2.0ASA v 2.0

CONCLUSIONSCONCLUSIONS

• The existing strong motion instrumentation, the recording infrastructure and the data processed in Mexico are the result of an enormous and sustained effort performed during 42 years.

• The implementation of Mex-SM-DB has made available the strong motion information gathered in México. Nowadays, we have around 650 accelerographic stations and about 22,350 accelerogram records.

• The methods for processing data include: offset correction, compute GPA, time drift adjustments, signal filtering and so on. For this, software provided by the manufacturers and domestic developed programs have been used.

• A significant stage of data processing is the conversion of the records into the Mexican Standard Acceleration File. This ASCII file format has been accepted for all the entities that integrate Mex-SM-DB for data dissemination.