Ground-motion attenuation in the Sacramento-San Joaquin delta, California, from 14 Bay Area earthquakes, including the 2014 M 6.0 South Napa earthquake
Bulletin of the Seismological Society of America
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Abstract
Peak ground motions (acceleration and velocity) radiated by earthquakes in the San Francisco Bay area and recorded within the Sacramento–San Joaquin Delta generally attenuate faster with distance than the Next Generation Attenuation-West2 ground-motion prediction equations (GMPEs). We evaluate the attenuation for a wide set of paths into the Delta by analyzing recorded ground motions from fourteen 4 ≤ M < 7 earthquakes located on major Bay area faults: the San Andreas, Calaveras, Hayward, West Napa, and Green Valley faults. We select stations within azimuthal ranges of 38°–114° into the Delta and calculate the residuals of the peak ground motions relative to the Boore et al. (2014) GMPEs. We then fit the natural log of these peak ground acceleration and peak ground velocity residuals for each earthquake to the function a−krγ, in which a is an event term and krγ is the differential attenuation. Although there is some variation in the differential attenuation obtained for each earthquake, the peak ground motions from most of the 14 events attenuate faster than predicted by the Boore et al. (2014) GMPEs. The differential attenuation does not appear to depend on azimuth or magnitude of the earthquake; however, earthquake depth may have an effect. Our results suggest that attenuation models for the Delta can be significantly improved through regionalization, although this regionalization will increase the model complexity and the epistemic uncertainty.
Suggested Citation
Erdem, J., Boatwright, J., and Fletcher, J.P., 2019, Ground-motion attenuation in the Sacramento-San Joaquin delta, California, from 14 Bay Area earthquakes, including the 2014 M 6.0 South Napa earthquake: Bulletin of the Seismological Society of America, v. 109, no. 3, p. 1025-1033, https://doi.org/10.1785/0120180182.
ISSN: 1943-3573 (online)
Study Area
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Ground-motion attenuation in the Sacramento-San Joaquin delta, California, from 14 Bay Area earthquakes, including the 2014 M 6.0 South Napa earthquake |
| Series title | Bulletin of the Seismological Society of America |
| DOI | 10.1785/0120180182 |
| Volume | 109 |
| Issue | 3 |
| Publication Date | April 16, 2019 |
| Year Published | 2019 |
| Language | English |
| Publisher | Seismological Society of America |
| Contributing office(s) | Earthquake Science Center |
| Description | 9 p. |
| First page | 1025 |
| Last page | 1033 |
| Country | United States |
| State | California |
| Other Geospatial | Sacramento-San Joaquin delta |