Strong-motion program report, January-December 1982

WilliAM P. ClARK, Secretary

FOREWARD

Records of strong ground shaking obtained from damaging earthquakes provide the basis for improving earthquake-resistant design and for understanding the nature of seismogenic failure in the Earth's crust. Strong-motion data acquired from the national network operated by the U.S. Geological Survey form a national resource for scientific research, engineering design, siting of critical structures, and safety evaluations for large-scale structures such as dams and bridges.

This report series, first initiated by the late R. B. Matthiesen after the damaging San Fernando earthquake of February 9, 1971, is intended to provide a catalog of strong-motion records recovered from the U.S. national network as well as summaries of related topics of special interest to the international earthquake-engineering research community. The collation of information presented in table l of this report series provides a complete list of all strong-motion records obtained from the national network, including those of relatively small amplitude (less than 0.05 .9. peak acceleration) that generally would not be digitized or otherwise processed unless warranted by a special studies request. Publication deadlines for this catalog are necessarily determined by instrumentation maintenance intervals (6 months to 2 years), which in turn determine the recovery period for much of the small amplitude data.

Recent developments in relational data base technology and improvements in mini- and micro-computer technology have provided opportunities to develop and implement improvements in data-dissemination procedures. Some of these improvements have been incorporated into standard dissemination procedures and others are in the process of being incorporated. Standard procedures currently implemented include:

l) Publication of data reports presenting processed recordings of large and damaging earthquakes of special interest, initially in the Open-file series and subsequently in the Bulletin series of the U.S. Geological Survey;

2) Commercial distribution of digital copies of published data by the National Geophysical Data Center, Boulder, Colorado;
3) Automatic dissemination via computer terminal of information in the Strong-Motion Information Retrieval System (SMIRS) for access by any interested user; and
4) A continuation of the catalog of strong-motion data recovered from the National Network, published annually in this series.

Procedures that are presently being developed to further facilitate dissemination of strong-motion data are based on recently developed relational data base technology. These efforts are directed toward development of a user friendly environment that will extend the capabilities of SMIRS by providing computer access to the digital time series, catalogs such as those published in this series, and the capability to quickly retrieve data subsets on the basis of a wide variety of user specified parameters.

These efforts, in support of the National Strong-Motion Program operated by the U.S. Geological Survey, which has responsibility for the acquisition, processing, and dissemination of all strong-motion data collected on the national network, are intended to facilitate the use of a scarce national resource, by the earthquake engineering and scientific research communities.

PREFACE

This Strong-Motion Program report gives preliminary information on the m~ture and availability of strong-motion data recorded by the U.S. Geological Survey (USGS). The program is operated by the USGS in cooperation with numerous Federal, State, and local agencies and private organizations. Major objectives of the program are to record both strong ground motion and the response of various types of engineered structures during earthquakes and to disseminate this information and data to the inte .. national earthquake-engineering research and design community.

This report contains a summary of the accelerograms recovered from the USGS National Strong-Motion network during 1982, notes on the availability of digitized data, and general information related to the USGS and to other strong-motion progrcms. The data summary in table l contains information on those accelerogramsrecovered (although not necessarily recorded) during 1982. Ronald L. Porcella, Editor U.S. Geological Survey, MS 977 Menlo Park, California 94025

iv

CONTENTS

• - - - iii 'Foreword -

The 1979 Imperial Valley Earthquake

Availability of strong-motion information and data

Table 1 -Summary of 1982 accelerograms

v

1982 STRONG-MOTION RECORDS

By J. C. Switzer

Two hundred and fifteen records were recovered from the USGS National Strong-Motion Network during 1982, just two fewer records than the yearly average for the period 1972 to 1981 inclusive. Thirteen records were recovered from a magnitude 4.5 earthquake on January 19 that was felt over all of the New England states and in parts of Quebec and Ontario. The largest recorded acceleration was 0.52 .9. at the right abutment of Franklin Falls Dam at an epicentral distance of about 8 km.

Earthquakes triggered ten strong-motion stations on the Island of Hawaii during the period September 1981 to May 1982 and produced a total of 38 records. A maximum horizontal acceleration of 0.58 .9. was recorded at Kau Hospital in Pahala located on the southern part of the island.

On June 15 a magnitude 4.8 earthquake occurred near Anza in southern California; ten accelerographs were triggered and seven records exceeded 0.05 .9. with a maximum peak acceleration of 0.14 .9. at Anza fire station.

A swarm of nine earthquakes between August 10 and August 12 produced ~0 records at the Bear Valley array southeast of Hollister, Calif. The magnitude 4.5 earthquake on August 10 produced a peak acceleration of 0.19 .9. at Bear Valley array station

12. During the magnitude 4.6 earthquake on August

ll a maximum acceleration of 0.27 .9. was recorded at the Bear Valley fire station.

In northern California a magnitude 4.6 earthquake on December 16 triggered four of six strong-motion recorders at the Eel River Valley array southeast of Eureka; the record from the Fortuna fire station showed a peak horizontal acceleration of 0.28 .9.· Additional strong-motion records recovered during 1982 were recorded at stations located in Alaska, Arkansas, California, Nevada, South Carolina, South Dakota, and Utah (see table l ). Event information listed in table 1 was taken primarily from Preliminary Determination of Epicenters, published monthly by the U~S. Geological Survey.

THE IMPERIAL VALLEY, CALIFORNIA, EARTHQUAKE OF OCTOBER 15,1979

From U.S. Geological Survey Professional

On October 15, 1979, the largest ear~hquake in California in the past decade occurre1 on the Imperial fault near the United States-Mexico border. whose epicenter was located in northern Mexico, damaged structures in and near the town of El Centro, Calif., was felt from Las Vegas~ Nev., to the Pacific Ocean, and was accompanied by surface movement on four fault zones. The earthquake caused an estimated $21.1 million in damage and injured 73 people, but no deaths were r~ported in the United States. The small number of injuries is indeed fortunate and is no doubt related to the fact that the areas of greatest population and number of manmade structures were not situated in the most strongly shaken area.

This volume contains 3 5 technical pa(:'ers on the following topics relating to the October 15 earthquake: faulting and other geologic investigatiors, damage and shaking-intensity studies, and strong-motion data and analyses. Depending on their subject matter, several papers are preliminary in nature, whereas others reflect indepth studies of a particular topic or data se.t.

Although the Imperial Valley is not densely developed, shaking-intensity studies usin~ manmade structures as primary indicators of the intensity of ground shaking yielded some interesting, if not controversial, findings. investigation of the distribution of intensity, for example, suggest some significant differences between the pattern of strong ground shaking during the 1940 and 1979 Imperial Valley earthquakes. One study focused on the performance of structures very Paper 1254, the "Introduction," by Carl E. Johnson, Christopher Rojahn, and Robert V. Sharp.

The moment-magnitude (M) f-.5 event,

Results of c regional close to the fault trace and another study concerned with the performance of a specific class of buildings prevalent throughout the valley both suggest that the intensity of ground shaking was not so severe as might have been expected on the basis of previously obtained data. The second study also shows a correlation between observed shaking effects and peak ground accelerations obtained from nearby strong-motion stations.

One of the primary difficulties in assessing the results from such shaking-intensity studies is, of course, that they are biased by the type of regional construction. heavily shaken area of the Imperial Valley, for example, were low-rise stiff buildings that respond predominantly to high-frequency ground motion; by contrast, there were few long-period structures (for example, mid- and high-rise buildings) that respond predominantly to longer period ground motions. Although the results from such studies should not be indiscriminately applied, they are nevertheless extremely valuable because they document the shaking effects on particular classes of structures during earthquakes.

With regard to the performance of engineered structures, the partial collapse of the six-story reinforced-concrete Building in El Centro and the complete collapse of an elevated steel water tank south of Brawley are particularly 9-year-old Imperial County Services Building was designed to resist earthquakes and was damaged so severely that it had to be demolished makes it an especially important cas2 study for the structural-engineering community.

This comprehensive set of strong-motion-accelerograph data yet recorded during a damaging earthquake. These data are unprecedented because they include the first set of ground-motion records ever obtained close to fault traces that were activated during a moderately strong earthquake, as well as the first set of records from an extensive array in a severely damaged building and from an extensive array on a highway overpass bridge less than l km from the fault rupture.

Of particular importance to engineering seismology are the data obtained from the El Centro ground-motion array, a 13-accelerograph 45-km-long linear array oriented perpendicular to and crossing the Imperial fault near El Centro; and from the El Centro differential array, a six-accelerograph 300-m-long linear differential ground motions due to horizontally propagating surface waves. from the 45-km-long array provide information on the nature of shaking close to and at increasing distance from the fault rupture, whereas those from the differential array are particularly applicable to the study of earthquake-induced stresses in such extended structures as bridges, dams, pipelines, and Most existing structures in the

noteworthy.

AVAILABILITY OF STRONG-MOTION DATA

most large mat foundations for nuclear power stations. These data also include the largest ~round acceleration yet recorded anywhere in the world.

From a structural-engineering point of view, the strong-motion data from the severely damaged six-story Imperial County Services B'Jilding in El Centro are undoubtedly the most obtained from this earthquake. Data from the building's 13-channel accelerograrh designed specifically for acquiring infcrmation that could lead to improvements in engineering design practice, provide a complete descripticn of building response before, during, and after the occurrence of severe structural damage. These data are exceptional because the time and mechanism of structural failure can be inferred directly from the recorded data. In conjunction with the records f~om a nearby free-field station, these data also provide important information on the extent of soil-structure interaction at the building site.

Overall, the strong-motion data recorded during the 1979 Imperial Valley earthquake and its aftershocks are expected to be of great value in many seismologic and earthquake-engineering studies. Such studies will undoubtedly provide more and better insights into the nature, causes, and effects of strong ground shaking.

Note: This publication is for sale by the U.S. Government Printing Office, Washington, D.C. 20402.

U. S. GEOLOGICAL SURVEY CAT A

Descriptions of strong-motion cccelerograph records and the circumstances in which they were recorded are available to anyone involved in earthquake engineering through the computer-based Strong-Motion Information Retrieval (SMIRS). SMIRS provides ready acce:ss to information about strong-motion records and .the level of processing and analysis that has been performed on them. Information about earthquakes that generated recorded motion and about the sites at which the motion was recorded is also provided.

With an ordinary phone line and a keyboard terminal, a SMIRS user may review the information free of charge. Once accessed, SMIR~ will offer a general introduction and will tell the user how to request more detailed instructions. The user also will be given an opportunity to request a copy of the printed user's manual.

SMIRS resides in one of the U.~. Geological Survey computers in Denver, Colorado. It can be accessed by telephoning the comruter center significant

System directly or by telephoning a local node in the TYMNET telecommunications network. The directdial telephone number for the Denver computer center is (303) 232-5309.

The TYMNET telecommunications network can be used to access SMIRS without incurring a long-distance telephone TYMNET Corporation maintains local telephone numbers in many cities in the United States and in several foreign countries. TYMNET phone numbers can be obtained from TYMNET Corporation's Customer Support Group at (800) 366-0149.

Take the following steps to connect your terminal to SMIRS.

1) Set the switches, keys, or buttons on the terminal that allow a choice of operating modes: transmission speed = 300 baud (30 characters

on line; lower case ASCII characters; and full duplex (if you are going to dial a

half duplex (if you are going to dial

2) Plug in and turn on the terminal; turn on the modem too if it is a separate device. Notice whether the modem uses an acoustic coupler or whether the modem is directly connected to a telephone. An acoustic coupler will have a cradle into which a telephone handset can be inserted. Look for a label or diagram on an acoustic coupler that will show you in which direction the telephone cord should go. A direct-connect modem will have a switch that can be set for voice or data transmission.
3) Telephone the USGS computer center in Denver or telephone the TYMNET number nearest you; wait for a high-pitched tone.
4) Place the telephone handset in the cradle on the acoustic coupler or set the direct-connect switch to "data." Wait for the "carrier detect" light to turn on; this indicates that the terminal is receiving a signal from the computer or from the TYMNET equipment.
5) If you telephoned the Denver computer center directly, skip this section, but if you telephoned a TYMNET number, the TYMNET prompts (shown underlined here) and your responses (shown in italics here) should proceed as follows:

please type your terminal identifier please log in:

The CR symbol represents the carriage-return key:

The "gsbc 1234" is what TYMNET refers to as a user name, the "2361" is a location identifier for the USGS computer center, and the "sandstone" is a password. "sandstone" will not be printed at your terminal charge to Denver.

per second) or 1200 baud;

Denver directly).

Note that the while you type.

Do not be alarmed if the first prompt comes at an odd speed.

TYMNET will now connect your terminal to a computer selecting device in Denver. If the computer selector is operating, "GSDN is online" will be printed at your terminal.

6) Type the carriage return key. The computer selecting device will ask you to "en~er class", to which you should answer "mult":

The selecting device will answer with several lines, something like "CONNEC~ING TO DENVER MUL TICS" and "class mult start".

7) Type the line-feed key. The MUL TICS computer will respond with several lines that will tell you which computer you have accessed, how many other users are connected, and S'J forth.

Ba) If your terminal will transmit both upper and lowercase characters, type:

The CR represents the carriage-return key and your name is your own na'Tle typed without any embedded blanks. It is good practice for you to choose a versicn of your name that will probably be unique, and to use that version of your name every time you log onto SMIRS. That way, any messag~~s sent to you through SMIRS will not be received by the wrong user.

Note that the word "enter" is in lowe .. case and "SMIRS" is in upper case. Bb) If your terminal has only uppercase characters, type:

9) From now on, SMIRS will prompt you whenever it expects you to type something. All the prompt lines begin and end with two dashes; answer by typing a question mark if you do not know what is expected of you.

Do not be concerned if the computer does not respond immediately after you enter SMIRS. The response time may improve in the future, but it will always be fastest during nonworking hours (Denver time).

CALIFORNIA DIVISION OF MINES AND GEOLOGY STRONG-MOTION OAT A

Processed strong-motion data from selected earthquakes are available from the California Division of Mines and Geology (CDMG). The data have been prepared by the strong-motion data processing system. This system is composed of a series of programs that have been developed by the California Institute of Technology, the USGS, and the CDMG, with special emphasis on the handling of long-duration film records from multiple-channel central recording instruments.

The data are grouped by phase:

Phase I Phase II

Phase III Each phase contains three-channel subgroups arranged by station. At the present time, data from the following earthquakes have been processed:

Santa Barbara earthquake of August 13, 1978

Station UCSB Goleta UCSB North Hall Freitas Building

Imperial Valley earthquake of October 15, 1979

El Centro free-field Imperial County Services Bldg.

The data are available on standard nine-track tapes, along with a microfiche copy of the tape contents. Interested parties should contact the CDMG Office of Strong-Motion Studies (see section "Data Sources").

It is the policy of the CDMG to make all strong-motion record data promptly available to the public in a manner consistent with good data management. Requests for copies of records, personal access to record or data files, and copies of data files should be made to the Chief, Office of Strong-Motion Studies (OSMS, see section "Data Sources") and should specify identity and medium of materials to be provided or reviewed. Desired access or delivery dates should be specific. When a request for copies of materials or personal access to files is received, OSMS staff will provide the requested material or will set an appointment time for personal review of files; the requestor will be notified immediately of any significant delay or other problems that prevent meeting the request. Charges for copying or other processing of materials will be based on the actual cost of producing and delivering the items, and OSMS will retain control of originals and master copies of all items. Uncorrected accelerations, Corrected velocities, and displacements, Response spectra. interim CDMG

FOREIGN STRONG-MOTION OAT A

Because of the long history of close cooperation between the United States and the Central and South American strong-motion programs, much of the data from those programs are available from the same sources as the United States date (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 obtcin 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 Strong-Motion Program Report series, and through informal arrangements, copies of the data and records are made available.

NOAA WORLDWIDE STRONG-MOTION OAT A

A worldwide collection of strong-motion seismograms for dissemination to the sdentific and engineering community is available from World Data Center A for Solid Earth Geophysi-::s, National Geophysical Data Center (NGDC). Countries contributing to the strong-motion data base include Australia, Italy, Japan, New Zealand, Rumania, U.S.S.R., and Yugoslavia. The USGS 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 list of most records can be o':ltained from the World Data Center A publication "Catalog of Seismograms and Strong-motion Reccrds," Report SE-6. This catalog can be ordered from NGDC (NOAA) for $3.00 (see section "Data Sources").

The most significant strong-mo':.ion records recorded in the United States and Latin America between 1931 and 1971 have been co~ied on seven reels of 35-mm film (xl2 reduction) and 70-mm film chips (approximately x8 reduction). The film chips are available for $1.50 per chip; longer records are continued on additional chips. The 35-mm film copies can be purchased for $30 p~r reel, the complete set of reels for $180. There is a minimum charge of $10 per order. Check with the National Geophysical Data Ce!lter for current prices before placing an order.

Other digitized data include punched cards containing strong-motion records from the March 4, 1977, Bucharest); the Gazli earthquake of May 17, 1976, in Uzbek, U.S.S.R.; 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 occurred in northern Italy near the town of Friuli in 1976; these were compiled by the National Commission for Nuclear Energy and have been given to the center for distribution. Other data include records obtained from California earthquakes near Santa Barbara in August 1978, Gilroy in August 1979, El Centro in October 1979, Livermore in January 1980, and Imperial Valley in April 1981.

A table listing all digitized strong-motion records available on magnetic tape may be obtained free of charge from NOAA. motion records may be purchased either in punched card components) or in tape format.

Checks or money orders should be made payable to "CommercefNOAA/NGDC"; inquiries should be addressed to NOAA (see section "Data Sources").

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

I. Branch of Distribution

604 S. Pickett Street Alexandria, VA 22304 earthquake

(804) 756-6141 (FTS) 756-6141 2.

8. Earthquake Engineering Research Institute 2620 Telegraph Avenue Berkeley, CA 94704

National Geophysical Data Center (D622) NOAA, Code E/GC 11 325 Broadway Street Boulder, CO 80303

National Technical Information Service 5285 Port Royal Road U.S. Dept. of Commerce Springfield, VA 22161

N ISEEfComputer Applications (415) 642-5113 519 Davis Hall, UC Berkeley Berkeley, CA 94720.

Office of Strong-Motion Studies California Division of Mines and Geology 2811 "0" Street Sacramento, CA 95816

Open-File Services Section Branch of Distribution

Box 25425, Federal Center Denver, CO 80225

345 Middlefield Rd., MS 977 Menlo Park, CA 94025. (415) 848-0972

(703) 487-4650 (FTS) 737-4650

(303) 234-5888 (FTS) 2:34-5888

(415) 323-8111 ext. 2881 (FTS) ~ 67-2881

20.080°N 155.465°W

l9.423°N 155.29l W 0.4 TT2, DirectionJ Max accl ou~ation S-t

1.6 2-peaks 1-peak

Table 1.- Swnmary of U.S. accelerograph records recovered during 1982- continue-:!

Pahala, Hawaii Kau Hospital (USGS) Station coord.

l9.752°N

1-peak

Table l. - Summary of U.S. acceZerograph records recovered during 1982 - continued

36.573°N 121. 184°W

ll5.487°W

30 December 1982 2319 UTC Central California Epicenter and magnitude unknown

lstation owner code: ACOE - U.S. Army Corps of Engineers. CDWR - California Department of Water Resources. CPA - City of Palo Alto. CLA - City of Los Angeles. MWD - Metropolitan Water District of Southern California. TEIC - Tennessee Earthquake Information Center. UCB - University of California, Berkeley. USBR - U.S. Bureau of Reclamation. USGS - U.S. Geological Survey. VA - Veterans Administration.

S-t - S-wave arrival minus trigger time (S - t) interval (S-P times given in parentheses).

Direction of case acceleration for upward trace deflection on accelerogram. Horizontal components are listed as azimuth in degrees clockwise from north. Vertical components are listed as "Up" or "Down ...

Peak acceleration recorded at ground level on one vertical and two orthogonal horizontal components unless otherwise noted.

Duration between first and last peaks of acceleration greater than 0.10 ~· t - WWVB time code not legible or instrument not equipped with a radio receiver; correlation of accelerogram with event may be questionable.

listed in event column).

* TT and/or S-t time is questionable or cannot be determined.

** Denotes maximum acceleration is less than 0.05 ~at ground level or less than 0.10 ~at non ground-level stations. Station name (owner)l

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