Interseismic Strain Accumulation on Faults Beneath Los Angeles, California
Abstract
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.
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 http://scedc.caltech.edu/research‐tools/alt‐2011‐dd‐hauksson‐yang‐shearer.html.Attached Files
Published - Rollins_et_al-2018-Journal_of_Geophysical_Research__Solid_Earth.pdf
Supplemental Material - downloadSupplement_doi=10.1029_2F2017JB015387_file=jgrb52928-sup-0001-JGRB52928_supplementary.pdf
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Additional details
- Eprint ID
- 93575
- Resolver ID
- CaltechAUTHORS:20190306-110634964
- NASA Earth and Space Science Fellowship
- Created
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2019-03-06Created from EPrint's datestamp field
- Updated
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2021-11-16Created from EPrint's last_modified field
- Caltech groups
- Seismological Laboratory, Division of Geological and Planetary Sciences (GPS)