Seismic engineering program report, September-December 1978

September - December 1978 United States Department of the Interior

PREFACE

Table 1 - Summary of accelerograms: September - December, 1978 - - 8 2 - Accelerograph data for southern Mexico earthquakes 3 - Strong-motion summary of Mexico aftershock records,

Figure 1 - Strong-motion stations triggered during southern of November 29, 1978- ------------------ 3 December 1978 to January 1979 -------------- 4

Mexico earthquake of November 29, 1978 and aftershocks -

of an offset in the short span of a bridge and substantial damage to the two-story administration building at Puerto Escondido Military Station (Nick Forell, oral commun., December 21, 1978).

Eight accelerograph records were obtained from instruments located at Mexico City, Malpaso Dam, Pajaritos, Minatitlan, and Oaxaca City. The maximum acceleration (0.22^) was recorded in the city of Oaxaca (see table 2). A report on the November 29 earthquake, which contains information obtained from the accelerographs listed in table 2 as well as from the Mexican seismic network of instruments located within a radius of 140 km of Mexico City, has been published (Espinosa and others, 1978); records from three of the stations in the Mexican seismic network have been digitized and their calculated spectra are included in the report.

On December 1, 1978, C. F. Knudson and P. N. Mork of the U.S. Geological Survey (USGS) flew to Mexico City to install a temporary accelerograph network in the epicentral area for the purpose of recording large aftershocks. With the assistance of J. Prince and other personnel of the Institute of Engineering of the National University, four accelerographs were installed in an east-west line from Puerto Angel to Pinotepa Nacional near the Pacific coast. Four additional accelerographs were installed along a north-south line from the city of Oaxaca to Puerto Escondido. Since Oaxaca, the largest city in southern Mexico, has a long history t)f damaging earthquakes, two USGS accelerographs were installed there to supplement the single permanent UNAM accelerograph now in place at the Colegio De Mexico in Oaxaca City (fig. 1).

Numerous small aftershocks have occurred in the epicentral area since the installation of the portable network. Accelerographs at three of the ten locations (Rancho Rosedal, Puerto Escondido, and San Gabriel Mixtepec) were triggered by aftershocks that occurred between December 8, 1978 and January 18, 1979. Time code generators installed on these instruments record the time of the aftershock (correct to within two minutes). All of the 10 aftershocks recorded during this 40-day period were small [x, less than 20 gal. From Espinosa and others, 1978.]

Coordinates Max. Record USGS Event Station °North °West Component accl. length epic. dist. time

~ just slightly above the triggering level of the instrument. The maximum acceleration (0.06c[) was recorded at San Gabriel Mixtepec on December 19, 1978 at 2210 UTC (table 3). The USGS aftershock network will be removed in April 1979 unless another large earthquake occurs in this region. References: Espinosa, J. M., Alonso, L., Mora, I., Cajiga, J., and Prince, J., 1978, Infonne preliminar sobre los sismos del 29 de Noviembre de 1978 en el Estedo de Oaxaca:

(gal) (sec) (km) (UTC)

Institute de Ingenieria, Ciudad Universitaria, Mexico, D.F., Informe IPS-4, 47 p. Forell, N., 1978, Quick-look report on the Oaxaca, Mexico earthquake, EERI reconnaissance team: Newsletter, Earthquake Engineering Research Institute, v. 13, n. 1, p. 6-10. Garza, T. and Lommitz, C., 1978, The Oaxaca gap:

A case history: Proceedings of conference VI, methodology for identifying seismic gaps and soon-to-break gaps: U.S. Geological Survey Open-file Report 78-943, p. 173-187.

Note that the word "enter" is in lower case, "SMIRS" is in upper case, and "name" can be either. If your terminal has only upper-case characters, type:

The "MAP" statement instructs the computer to interpret all the alphabetic characters you will subsequently type as though they were in lower case, excepting those characters that follow a left slant (). From now on, the system will prompt you whenever it expects you to type something. All the prompt lines begin and end with two dashes. Answer by typing the question-mark key if you do not know what is expected of you.

If you have a terminal that will not operate in the appropriate modes, or if other access problems arise, contact April Converse (415) 323-8111, ext. 2881 or FTS 467-2881.

One of the major tasks of the U.S. Geological Survey (USGS) as regards seismic engineering is the collection and dissemination of strong-motion accelerograph records. In analyzing these records, certain information describing the instrument site is important: local geology; instrument housing (buildings, dams, bridges, instrument shelters); local topography; and proximity of an accelerograph to man-made structures that might influence the record. A series of reports that summarize the site information in the USGS files is being prepared. These reports describe local geologic conditions of selected sites and will cover strong-motion accelerograph sites in the western hemisphere. Station locations described in Parts I and II include 18 in California, 5 in Washington, and 1 each in Arizona, Montana, Nevada, New York, and Utah. Reference: U.S. Geological Survey Open-file Reports 78-1005 (Part I), 1978, 40 p. and 79-428 (Part II), 1979, 34 p. MAP return linefeed ENTER your-name \S\M\I\R\S return linefeed

by B. L. Silverstein A Strong-Motion Information Retrieval System (SMIRS) has been developed to provide up-todate information about strong-motion records and the circumstances in which they were recorded to anyone having a computer data terminal (see p.5). The system is operating, but the information within it is incomplete and needs to be verified. A user's manual is available (Converse, 1978).

The strong-motion records from the February 9, 1971 San Fernando, California earthquake and most of the significant records prior to that event have been digitized by the California Institute of Technology (CIT) (Hudson, 1976). Processing and analysis of the data have been presented in a series of reports containing (1) uncorrected digital data, (2) corrected accelerations, velocities, and displacements, (3) response spectra, and (4) Fourier amplitude spectra. All of these data reports are available through the National Technical Information Service (NTIS).

The digitization and analysis of the significant records subsequent to the San Fernando earthquake have been carried out by the U.S. Geological Survey (USGS). Processing and analysis of this data are presented in a series of USGS Open-file Reports. When published, these reports are available from the USGS, Open-File Services Section.

The digitization and analysis of the records collected by the State of California Strong-Motion Instrumentation Program are being handled by the Office of Strong-Motion Studies (OSMS), California Division of Mines and Geology. When completed, reports on these analyses will be available from OSMS (Porter and others, 1979).

The digitized data from the CIT digitization program are available from the Environmental Data Service (EDS) and the National Information Service for Earthquake Engineering at the University of California, Berkeley (NISEE). The magnetic tape digital data from subsequent years will be available from EDS and NISEE at approximately the same time as the data reports are published. References: Converse, A., 1978, Strong-motion information retrieval system user's manual: U.S. Geological Survey Open-file Report 79-289, 51 p. Hudson, D. E., 1976, Strong-motion earthquake accelerograms - index volume: California Institute of Technology, EERI report 76-02, 72 p. Porter, L. D., Ragsdale, J. T., and McJunkin, R. D., 1979, Processed data from the partial strong-motion records of the Santa Barbara earthquake of 13 August 1978 preliminary results: California Division of Mines and Geology, PR-23, 93 p.

Because of the long history of close cooperation between the U.S. and the Central and South American strong-motion programs, much of the data from those programs is available from the same sources as the U.S. data (see below). Information about strong-motion data from the western hemisphere will be included in the Strong-Motion Information Retrieval System operated by the USGS.

The USGS does not attempt to obtain first-class copies of records from those foreign organizations that prepare data reports comparable to those prepared by the USGS. Abstracts of the data reports from such organizations are presented in this Seismic Engineering Program Report series, and through informal arrangements, copies of the data and records are made available. The Environmental Data Service of NOAA has attempted to obtain copies of digitized strong-motion data from all organizations worldwide (see the following section).

A worldwide collection of strong-motion seismograms for dissemination to the scientific and engineering community is available from World Data Center A for Solid Earth Geophysics and the National Geophysical and Solar-Terrestrial Data Center. Countries contributing to the strong-motion data base include Australia, Italy, Japan, New Zealand, Rumania, U.S.S.R., and Yugoslavia. The U.S. Geological Survey has furnished records from its network of cooperative strong-motion stations, including those in Central and South America.

Copies of strong-motion records are available on 35-mm film, on 70-mm film chips, as paper copies, and as digitized data on punched cards or magnetic tape. A listing of most records can be obtained from the World Data Center A publication "Catalog of Seismograms and Strong-Motion Records, Report SE-6." This catalog can be ordered from NGSDC for $2.00.

The most significant strong-motion records recorded in the United States and Latin America between 1931 and 1971 have been copied on eight reels of 35-mm film (12x reduction) and 70-mm film chips (approximately 8x reduction). The film chips are available for $.50 per chip. Longer records are continued on additional chips. The 35-mm film copies can be purchased for $20 per reel, the complete set of eight reels for $130.

Full-size paper copies (12" x 36") are available for many of the events in the United States and Latin America at a cost of $1.50 per record. Other records are available as paper copies, but at a reduced scale.

Japan and Australia have supplied magnetic tapes of digitized data from stations located in the western Pacific Ocean (the Japanese Islands, New Guinea, and New Britain). A series of 400 U.S. strong-motion records (1933-1971) were digitized by the California Institute of Technology and are now available on six magnetic tapes. The U.S. Geological Survey is digitizing post-1971 records from its network. They have generated five tapes of strong-motion records recorded from 1967 to 1975 in the United States and Latin America (Chile, Nicaragua, San Salvador, and Mexico).

Other digitized data recently received are punched cards containing strong-motion records from the March 4, 1977 earthquake in Rumania (recorded in Bucharest); the Gazli earthquake of May 17, 1976, in Uzbek, USSR; and three earthquakes in the New Madrid seismic zone (located in midcontinental United States) in 1975 and 1976.

Recent acquisitions include a magnetic tape of strong-motion records triggered by a swarm of earthquakes that rocked northern Italy near the town of Friuli in 1976; these were compiled by the National Commission for Nuclear Energy (CNEN) and have been given to the Center for distribution.

A table listing all digitized strong-motion records available on magnetic tape may be obtained free of charge from EDS/NOAA. Digitized strong-motion records may be purchased either in punched card format at $20 per record (including all three instrument components) or in tape format at $60 per tape.

Checks or money orders should be made payable to "Commerce/NOAA/NGSDC"; inquiries should be addressed to EDS/NOAA (see address below). Phone: (303) 499-1000, ext. 6744; FTS phone: 323-6477.

For reports or data regarding strong-motion records and data, address inquiries to the appropriate agency listed below:

1. EDS/NOAA
2. NISEE/Computer Applications
3. Open-file Services Section

National Geophysical and Solar-Terrestrial Data Center (D62) Boulder, CO 80302 Davis Hall, UC Berkeley Berkeley, CA 94720 Branch of Distribution Box 25425, Federal Center Denver, CO 80225 Event Station name Station S-t 2 Accl Max acc"N Durations

4 October 1978 Pine Flat Dam 36.83 N - ** 1642 UTC (ACOE)t 119.33 W Bishop, Calif. 37.53N, 118.66W Magnitude 5.7

1 ACOE - U.S. Army Corps of Engineers USGS - U.S. Geological Survey T WWVB time code is incomplete or nonexistent; correlation of accelerogram with event is questionable. 2 S-wave minus trigger time.

• Accelerograph equipped with horizontal starter; S-t time is not significant.

3 Azimuthal direction of case acceleration for upward trace deflection on accelerogram (opposite direction to pendulum motion). 4 Unless otherwise noted, maximum acceleration recorded at ground or basement level.

** Denotes maximum acceleration is less than 0.05 £ at ground stations or less than 0.10 ct at upper floors of buildings. 5 Duration for which peaks of acceleration exceed 0.10 £. (owner)^ coord. (s) directions (c[) (s)

Note: One event recorded at stations located at the toe,

Buchanan Dam 37.22 N ** (ACOE)t 119.98 W Note: One event recorded at stations located at the crest, downstream, and outlet tower levels 2 and 5; maximum acceleration less than 0.05 c[.

abutment, and outlet tower upper and lower levels; maximum acceleration less than 0.05 3.

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