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OSMS 89-06

by A. Shakal, M. Huang, M. Reichle, C. Ventura, T. Cao, R. Sherburne, M. Savage, R. Darragh and C. Petersen

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Introduction

Strong-motion records were recovered from 93 stations of the California Strong Motion Instrumentation Program (CSMIP) after the earthquake of October 17, 1989 which occurred in the Santa Cruz Mountains. The epicenter was approximately 16 km east of Santa Cruz and 33 km southwest of San Jose. The 93 stations from which CSMIP recovered data include 53 ground-response stations and 40 extensively-instrumented structures. The most distant stations were approximately 175 km from the earthquake (Santa Rosa and Bodega Bay); 25 records were obtained within 40 km of the epicenter. The 40 extensively-instrumented structures include 33 buildings, two dams, two freeway overpasses, a wharf, a tunnel and a rapid-transit structure. This report includes all CSMIP data from this earthquake and supersedes the quick reports distributed on October 17 and 25 (CDMG, 1989 a,b).

The estimated earthquake location and magnitude are:
           Epicenter: 37.037N, 121.883W. Depth: 18 km (USGS)
           Origin Time: 00:04:02, 18 Oct 1989 GMT. (5:04 pm, 17 Oct 1987 PDT)
           Magnitude: 7.0 ML (BRK); 7.1 MS (NEIS).

Damage was extensive in the coastal area west of the San Andreas fault, from Santa Cruz to Watsonville. Damage was also severe in localized areas in the San Francisco Bay area. A collection of damage studies by various individuals and institutions is being prepared by the Earthquake Engineering Research Institute.