Station. Accelerogram Station Accelerogram

Transcription

1 RECORD PROCESSING METHODS AND PROCEDURES FOR THE MEXICAN STRONG MOTION PROGRAM Leonardo Alcántara N Citlali Pérez Y Engineering Institute, National Autonomous University of Mexico (UNAM)

2 Main seismic events in Mexico

3 Distribution of the Mexican Accelerographic Network

4 Station Accelerogram Station Accelerogram Accelerographs and records gotten in MEXANET from 1960 to 2004

5 Architecture of the Mexican Strong Motion Database

6 Structure of the ASCII Standard Acceleration File

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

8 First stage on seismic i data processing

9 Standard Processing Offset correction. In order to eliminate the static acceleration to the signal. Search for GPA. Most of the programs give the values of peak accelerations although they are not always in gal units. 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 triggered the station. Consulting the epicenter location catalogs issued by the Mexican Seismological i l Service.

10 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 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.

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

12 Col Col Col 1. 1*************************************40*************************************80 2. INSTITUTO DE INGENIERIA, UNAM 3. Coordinacion de Instrumentacion Sismica 4. Ciudad Universitaria, Apartado Postal , Mexico, D.F. 5. Tel. (525) , Fax. (525) , 6. ******************************************************************************** 7. MEXICAN STANDARD ACCELERATION FILE 8. FORMAT VERSION : FILE NAME : COPL DATE AND TIME OF CREATION : September 25, 1995/14:38: REF. ACCELERATION CATALOG, SMIS 1995 : NUM. REG. 1355/PAG ================================================================================ 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 : LAT. N 24. : LONG. W 25. ALTITUDE (meters) : SOIL TYPE : Weathered Granite Gneiss 27. : 28. : 29. INSTITUTION IN CHARGE OF ITS OPERATION : Instituto t de Ingeniería, UNAM 30. : Coordinacion de Instrumentacion Sismica ================================================================================ 33. INFORMATION ABOUT THE ACCELEROGRAPH 34. ACCELEROGRAPH MODEL : DCA SERIAL NUMBER : NUMBER OF CHANNELS : ORIENTATION C1-C6 (bearing;orientation): /V/N90E/N00E 38. ORIENTATION C7-C12 (bear.;orientation) : 39. SAMPLING SPEED, C1-C6 (samples/sec) : /100/100/ 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/ SENSORS NAT. FREQUENCY, C7-C12, (Hz) : 45. SENSORS DAMPING, C1-C6 : /0.71/0.72/ SENSORS DAMPING, C7-C12 : 47. SAMPLING INTERVAL, C1-C6, (sec) : /0.01/0.01/ 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) : POST-EVENT MEMORY (sec) : ================================================================================ 56. INFORMATION ABOUT THE EARTHQUAKE 57. DATE OF THE EARTHQUAKE (GMT) : September 14, EPICENTRAL TIME (GMT) : 14:04: MAGNITUDE(S) : /Mb=6.5/Ms=7.2/Mw= EPICENTER LOCATION : LAT. N 61. : LONG. W 62. FOCAL DEPTH (km) : INFORMATION SOURCE : Instituto de Geofisica, UNAM 64. : Servicio Sismologico Nacional ================================================================================ 67. INFORMATION ABOUT THIS RECORD 68. TIME OF THE FIRST SAMPLE (GMT) : 14:04: RECORDING TIME PRECISION (sec) : RECORD DURATION (sec), C1-C6 : /63.15/63.15/ RECORD DURATION (sec), C7-C12 : 72. TOTAL No. OF SAMPLES, C1-C6 : /6315/6315/ TOTAL No. OF SAMPLES, C7-C12 : 74. PEAK ACCELERATION (Gal), C1-C6 : /46.42/68.91/ PEAK ACCELERATION,C1-C6, AT SAMPLE No. : /1246/1326/ 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 : DATA FORMAT (FORTRAN,10 fields/sample) : 3F ================================================================================ 84. QUALITY OF THE ACCELEROGRAM 85. Complete digital record with correct absolute time ================================================================================ 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 ================================================================================ 105. ACCELERATION DATA: CHANNEL-1 CHANNEL-2 CHANNEL-3 CHANNEL-4 CHANNEL-5 CHANNEL-6 CHANNEL-7 CHANNEL V N90E N00E Mexican Standard Acceleration File, ASA v 2.0

13 CONCLUSIONS 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 d Acceleration File. This ASCII file format has been accepted for all the entities that integrate Mex-SM-DB for data dissemination.