HR: 1340h
AN: OS23D-1354    [Abstracts]
TI: Tsunami Hazards in San Francisco Bay
AU: * Dengler, L
EM: lad1@humboldt.edu
AF: Humboldt State University, Dept. of Geology, Arcata, CA 95521 United States
AU: Borrero, J
EM: jborrero@usc.edu
AF: Univ. of Southern California, Dept. of Civil Engineering, Los Angeles, CA 90089 United States
AU: Patton, J
EM: jrpatton@northcoast.com
AF: Humboldt State University, Dept. of Geology, Arcata, CA 95521 United States
AB: A prerequisite to probabilistic hazard assessment is a historic event database and identification of all potential sources. We review published and unpublished material to compile a history of tsunami events, peak tsunami heights and tsunami source regions for San Francisco Bay. Since 1850, 51 credible tsunamis have been recorded or observed within the San Francisco Bay area, all but 6 teletsunamis. Only the tsunamis generated by the 1960 Chile earthquake and the 1964 Alaska earthquake caused damage in San Francisco Bay. Both events are characterized by long duration (12 hours) short period oscillations (about 30 minutes) attributed to near-resonance within the Bay (Wilson and Torum, 1968). Magoon (1966) developed an attenuation relation based on the 1960 and 1964 events and shows an amplitude decay by 50 percent of the Presidio value at Alameda and a 90 percent decrease at the northern and southern ends of the Bay. The 1964 tsunami was the most damaging historic event and caused about 177,000 (US dollars) in damages to boats and floating structures, with 1.13 m amplitude waves recorded at the Presidio. Six credible local tsunami events were observed between 1851 and 1906, four attributed to earthquake sources and two to landslides. The largest (0.6 m near Benicia) was caused by the 1898 Mare Island earthquake and is attributed to slip on the Rogers Creep fault. Garcia and Houston (1975) made return estimates for San Francisco Bay, considering only Alaska sources and estimated 100- and 500-year heights of 2.5 and 4.8 meters respectively at the Presidio. These values need to be reassessed in light of other credible teletsunami sources, particularly the Cascadia subduction zone, and local sources including step-overs on regional strike-slip faults and landslides within the bay. We present the results of numerical modeling runs to test Magoon's attenuation models and to compare local and teletsunami source regions.
DE: 7223 Seismic hazard assessment and prediction
DE: 4564 Tsunamis and storm surges
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting