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Chapter B. The Loma Prieta, California, Earthquake of October 17, 1989 - Forecasts

July 1, 1998

The magnitude (Mw) 6.9 Loma Prieta earthquake struck the San Francisco Bay region of central California at 5:04 p.m. P.d.t. on October 17, 1989, killing 62 people and generating billions of dollars in property damage. Scientists were not surprised by the occurrence of a destructive earthquake in this region and had, in fact, been attempting to forecast the location of the next large earthquake in the San Francisco Bay region for decades. This paper summarizes more than 20 scientifically based forecasts made before the 1989 Loma Prieta earthquake for a large earthquake that might occur in the Loma Prieta area. The forecasts geographically closest to the actual earthquake primarily consisted of right-lateral strike-slip motion on the San Andreas Fault northwest of San Juan Bautista. Several of the forecasts did encompass the magnitude of the actual earthquake, and at least one approximately encompassed the along-strike rupture length. The 1989 Loma Prieta earthquake differed from most of the forecasted events in two ways: (1) it occurred with considerable dip-slip in addition to strike-slip motion, and (2) it was much deeper than expected.

Citation Information

Publication Year 1998
Title Chapter B. The Loma Prieta, California, Earthquake of October 17, 1989 - Forecasts
DOI 10.3133/pp1550B
Authors Ruth A. Harris
Publication Type Report
Publication Subtype USGS Numbered Series
Series Title Professional Paper
Series Number 1550
Index ID pp1550B
Record Source USGS Publications Warehouse
USGS Organization Earthquake Hazards Program; Earthquake Science Center

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