Seismic activity of the San Francisco Bay region

W. H. Bakun

doi:10.1785/bssa0890030764

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Seismic activity of the San Francisco Bay region

W. H. Bakun

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Abstract

Moment magnitude M with objective confidence-level uncertainties are estimated for felt San Francisco Bay region earthquakes using Bakun and Went-worth's (1997) analysis strategy for seismic intensity observations. The frequency-magnitude distribution is well described for M ≧ 5.5 events since 1850 by a Gutenberg-Richter relation with a b -value of 0.90. The seismic moment rate Σ M 0 /yr since 1836 is 2.68 × 10 18 N-m/yr (95% confidence range = 1.29 × 10 18 N-m/yr to 4.07 × 10 18 N-m/yr); the seismic moment rate since 1850 is nearly the same. Σ M 0 /yr in the 56 years before 1906 is about 10 times that in the 70 years after 1906. In contrast, Σ M 0 /yr since 1977 is about equal that in the 56 years before 1906. 80% (1σ = 14%) of the plate-motion moment accumulation rate is available for release in earthquakes. The historical Σ M 0 /yr and the portion of the plate-motion moment accumulation rate available for release in earthquakes are used in a seismic cycle model to estimate the rate of seismic activity in the twenty-first century. High and low rates of future seismic activity are both permissible given the range of possible seismic-cycle recurrence times T and the uncertainties in the historical Σ M 0 and in the percentage of plate motion available for release in earthquakes. If the historical seismic moment rate is not greater than the estimated 2.68 × 10 18 N-m/yr and the percentage of the plate-motion moment accumulation available for release in earthquakes is not less than the estimated 80%, then for all T , the rate of seismic moment release from now until the next 1906-sized shock will be comparable to the rate from 1836 to 1905 when M 6 1/2 shocks occurred every 15 to 20 years.

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Bulletin of the Seismological Society of America Article

Source-reported bounding extent: 37.06612126487765° to 38.61368573647616° latitude; -123.46967985950582° to -121.30089136854097° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

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BibTeX RIS

W. H. Bakun. 1999-06-01. Seismic activity of the San Francisco Bay region. https://doi.org/10.1785/bssa0890030764

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