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Postseismic Deformation Following the 2010 M=7.2 El Mayor-Cucapah Earthquake: Observations, Kinematic Inversions, and Dynamic Models

Rollins, Christopher and Barbot, Sylvain and Avouac, Jean-Philippe (2015) Postseismic Deformation Following the 2010 M=7.2 El Mayor-Cucapah Earthquake: Observations, Kinematic Inversions, and Dynamic Models. Pure and Applied Geophysics, 172 (5). pp. 1305-1358. ISSN 0033-4553 . http://resolver.caltech.edu/CaltechAUTHORS:20150430-091229989

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Abstract

Due to its location on a transtensional section of the Pacific-North American plate boundary, the Salton Trough is a region featuring large strike-slip earthquakes within a regime of shallow asthenosphere, high heat flow, and complex faulting, and so postseismic deformation there may feature enhanced viscoelastic relaxation and afterslip that is particularly detectable at the surface. The 2010 M=7.2 El Mayor-Cucapah earthquake was the largest shock in the Salton Trough since 1892 and occurred close to the US-Mexico border, and so the postseismic deformation recorded by the continuous GPS network of southern California provides an opportunity to study the rheology of this region. Three-year postseismic transients extracted from GPS displacement time-series show four key features: (1) 1–2 cm of cumulative uplift in the Imperial Valley and ∼ 1 cm of subsidence in the Peninsular Ranges, (2) relatively large cumulative horizontal displacements > 150 km from the rupture in the Peninsular Ranges, (3) rapidly decaying horizontal displacement rates in the first few months after the earthquake in the Imperial Valley, and (4) sustained horizontal velocities, following the rapid early motions, that were still visibly ongoing 3 years after the earthquake. Kinematic inversions show that the cumulative 3-year postseismic displacement field can be well fit by afterslip on and below the coseismic rupture, though these solutions require afterslip with a total moment equivalent to at least a M=7.2 earthquake and higher slip magnitudes than those predicted by coseismic stress changes. Forward modeling shows that stress-driven afterslip and viscoelastic relaxation in various configurations within the lithosphere can reproduce the early and later horizontal velocities in the Imperial Valley, while Newtonian viscoelastic relaxation in the asthenosphere can reproduce the uplift in the Imperial Valley and the subsidence and large westward displacements in the Peninsular Ranges. We present two forward models of dynamically coupled deformation mechanisms that fit the postseismic transient well: a model combining afterslip in the lower crust, Newtonian viscoelastic relaxation in a localized zone in the lower crust beneath areas of high heat flow and geothermal activity, and Newtonian viscoelastic relaxation in the asthenosphere; and a second model that replaces the afterslip in the first model with viscoelastic relaxation with a stress-dependent viscosity in the mantle. The rheology of this high-heat-flow, high-strain-rate region may incorporate elements of both these models and may well be more complex than either of them.


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http://dx.doi.org/10.1007/s00024-014-1005-6 DOIArticle
http://link.springer.com/article/10.1007%2Fs00024-014-1005-6PublisherArticle
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ORCID:
AuthorORCID
Rollins, Christopher0000-0002-5291-6956
Avouac, Jean-Philippe0000-0002-3060-8442
Additional Information:© 2015 Springer. Received March 3, 2014, revised November 26, 2014, accepted November 27, 2014, online date January 21, 2015.
Group:Seismological Laboratory
Record Number:CaltechAUTHORS:20150430-091229989
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20150430-091229989
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:57107
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:30 Apr 2015 20:24
Last Modified:01 Sep 2017 16:59

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