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Interseismic Strain Accumulation on Faults Beneath Los Angeles, California

Rollins, Chris and Avouac, Jean-Philippe and Landry, Walter and Argus, Donald F. and Barbot, Sylvain (2018) Interseismic Strain Accumulation on Faults Beneath Los Angeles, California. Journal of Geophysical Research. Solid Earth, 123 (8). pp. 7126-7150. ISSN 2169-9313. doi:10.1029/2017jb015387.

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Geodetic data show that the Los Angeles metropolitan area is undergoing 8–9 mm/year of north‐south tectonic shortening associated with the Big Bend of the San Andreas Fault. This shortening has been linked to multiple damaging twentieth century thrust earthquakes as well as possible Mw ≥ 7.0 Holocene thrust events beneath central Los Angeles. To better characterize this seismic hazard, we assess how this shortening is being accommodated by interseismic strain accumulation on subsurface faults, incorporating detailed seismology‐ and geology‐based models of fault geometry and the low‐stiffness Los Angeles sedimentary basin. We find that strain accumulation on local strike‐slip faults likely contributes no more than 1–2 mm/year of the shortening. We formally invert the geodetic data for the pattern of interseismic strain accumulation on the north dipping Sierra Madre, Puente Hills, and Compton thrust faults and a master decollement. We explore the impact of the assumed material model, strain accumulation on faults to the west and east, and other model assumptions. We infer that the three faults slip at 3–4 mm/year over the long term and are currently partially or fully locked and accruing interseismic strain on their upper sections. This locking implies an annual deficit of seismic moment, 1.6 + 1.3/−0.5 × 10^(17) Nm/year in total, which is presumably balanced over the long‐term average by the moment released in earthquakes. The depth distribution of moment deficit accumulation rate matches that of seismicity rates in Los Angeles to first order, in part, because the models incorporate the blind nature of the Puente Hills and Compton Faults.

Item Type:Article
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URLURL TypeDescription
Rollins, Chris0000-0002-5291-6956
Avouac, Jean-Philippe0000-0002-3060-8442
Argus, Donald F.0000-0002-2770-4257
Barbot, Sylvain0000-0003-4257-7409
Additional Information:© 2018. American Geophysical Union. Received 22 DEC 2017. Accepted 9 JUL 2018. Accepted article online 16 JUL 2018. Published online 30 AUG 2018. C. Rollins was supported by the NASA Earth and Space Science Fellowship for the duration of this work. The authors are grateful to Scott T. Marshall and two anonymous reviewers for suggestions that greatly improved the manuscript, as well as numerous colleagues around the community for helpful input and guidance. The authors declare no competing financial interests. The GPS data used here can be found in Argus et al. (2005), Table 3; the HYS16 seismic catalog is available at‐tools/alt‐2011‐dd‐hauksson‐yang‐shearer.html.
Group:Seismological Laboratory
Funding AgencyGrant Number
NASA Earth and Space Science FellowshipUNSPECIFIED
Issue or Number:8
Record Number:CaltechAUTHORS:20190306-110634964
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Official Citation:Rollins, C., Avouac, J.‐P., Landry, W., Argus, D. F., & Barbot, S. (2018). Interseismic strain accumulation on faults beneath Los Angeles, California. Journal of Geophysical Research: Solid Earth, 123, 7126–7150.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:93575
Deposited By: George Porter
Deposited On:06 Mar 2019 19:22
Last Modified:16 Nov 2021 16:59

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