Re-evaluation of several large historic earthquakes in the vicinity of the Loma Prieta and peninsular segments of the San Andreas fault, California

摘要: Abstract The size and location of several the largest 19th century earthquakes in San Francisco Bay area, including June 1838, 8 October 1865, 21 1868, 24 April 1890 events, are re-evaluated by comparing these historic events to modern particular 1989 Loma Prieta earthquake. Similar high intensities Monterey area during both 1838 indicate that shock probably ruptured segment addition Peninsular Andreas fault. If so, resulting earthquake would have been moment magnitude M W ≧ 7.2. Thus, like segments many other plate boundaries, exhibits heterogeneous rupture sometimes it ruptures with segment, as 1906 at times alone, 1989. In contrast, generated 1865 was centered Santa Clara Valley eastern foothills Cruz Mountains, indicating located northeast not on addition, felt areas, taken be one best measures relative source size, modified Mercalli (MMI) V VI for considerably smaller than event. Relationships between areas developed area. Based relationships, average computed magnitudes 6.51 ± 0.18, 6.84 0.20, 6.32 0.16, respectively. results correct, then include all faults within fault zone, i.e., a zone up few kilometers wide, appears or without every 76 11 years. These data repeat may most accurate information now available ascertaining date future testing recurrence models. consistent being part long-term seismic build-up 1868 event rather paired similar size. did occur type, closer Jose Valley, could pose considerable hazard southern On-going searches letters diaries missionaries early settlers yield new should help further constrain locations earthquakes.