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Seismicity and Active Compressional Tectonics in Santa Monica Bay, Southern California

Hauksson, Egill and Saldivar, Geoffrey V. (1989) Seismicity and Active Compressional Tectonics in Santa Monica Bay, Southern California. Journal of Geophysical Research B, 94 (B7). pp. 9591-9606. ISSN 0148-0227. doi:10.1029/JB094iB07p09591.

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During 1973–1986 the seismicity in Santa Monica Bay consisted of an average of four events per year of M_L ≥ 2.5, in addition to the 1979 Malibu (M_L = 5.0) mainshock-aftershock sequence. The 1979 sequence ruptured a north dipping thrust fault at 10–15 km depth beneath the bay. A diffuse distribution of seismicity extends across the bay from the terminus of the Palos Verdes fault to Point Dume. Two thirds of the single-event focal mechanisms of 36 events that are located within the bay show mostly thrust or reverse faulting on west to west-northwest striking planes. A third of the focal mechanisms exhibit strike-slip faulting on north to north-northwest striking planes. A stress inversion of the focal mechanism data shows that the maximum principal stress is oriented N13°E in a horizontal plane and the minimum principal stress is oriented N102°E and plunging 47°. Hence the tectonics in Santa Monica Bay are dominated by compression, with thrust, reverse, and strike-slip faulting. The coexistence of thrust and strike-slip faults suggests that the bay is not a part of the Peninsular Ranges terrane but forms a transition zone that accommodates the change from strike-slip in the Peninsular Ranges to the south to reverse faulting in the Transverse Ranges to the north. Mapped anticlines and the previously unrecognized thrust faults beneath the bay form two fold and thrust belts that present additional seismic hazards to Los Angeles and the southern California coastal zone through seismic shaking and possible generation of small tsunamis.

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Hauksson, Egill0000-0002-6834-5051
Additional Information:© 1989 American Geophysical Union. Manuscript Accepted: 18 January 1989; Manuscript Received: 14 September 1988. We thank William Ellsworth, Peter Malin, Ross Stein, Lucile Jones, and John McRaney for critical reviews of the manuscript. This research was supported by USGS grant 14-08-0001-G1328 and USGS cooperative agreement 14-08-0001-A0264.
Group:Seismological Laboratory
Funding AgencyGrant Number
Subject Keywords:Continental neotectonics; Continental tectonics: extensional; Continental tectonics: general; Information Related to Geographic Region: North America; Oceanic crust; Seismicity and tectonics; Structural geology
Issue or Number:B7
Record Number:CaltechAUTHORS:20130417-104409794
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Official Citation:Hauksson, E., and G. V. Saldivar (1989), Seismicity and active compressional tectonics in Santa Monica Bay, southern California, J. Geophys. Res., 94(B7), 9591–9606, doi:10.1029/JB094iB07p09591.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:37986
Deposited On:19 Apr 2013 16:27
Last Modified:09 Nov 2021 23:32

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