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Rayleigh and S wave tomography constraints on subduction termination and lithospheric foundering in central California

Jiang, Chengxin and Schmandt, Brandon and Hansen, Steven M. and Dougherty, Sara L. and Clayton, Robert W. and Farrell, Jamie and Lin, Fan-Chi (2018) Rayleigh and S wave tomography constraints on subduction termination and lithospheric foundering in central California. Earth and Planetary Science Letters, 488 . pp. 14-26. ISSN 0012-821X. doi:10.1016/j.epsl.2018.02.009.

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The crust and upper mantle structure of central California have been modified by subduction termination, growth of the San Andreas plate boundary fault system, and small-scale upper mantle convection since the early Miocene. Here we investigate the contributions of these processes to the creation of the Isabella Anomaly, which is a high seismic velocity volume in the upper mantle. There are two types of hypotheses for its origin. One is that it is the foundered mafic lower crust and mantle lithosphere of the southern Sierra Nevada batholith. The alternative suggests that it is a fossil slab connected to the Monterey microplate. A dense broadband seismic transect was deployed from the coast to the western Sierra Nevada to fill in the least sampled areas above the Isabella Anomaly, and regional-scale Rayleigh and S wave tomography are used to evaluate the two hypotheses. New shear velocity (Vs) tomography images a high-velocity anomaly beneath coastal California that is sub-horizontal at depths of ∼40–80 km. East of the San Andreas Fault a continuous extension of the high-velocity anomaly dips east and is located beneath the Sierra Nevada at ∼150–200 km depth. The western position of the Isabella Anomaly in the uppermost mantle is inconsistent with earlier interpretations that the Isabella Anomaly is connected to actively foundering foothills lower crust. Based on the new Vs images, we interpret that the Isabella Anomaly is not the dense destabilized root of the Sierra Nevada, but rather a remnant of Miocene subduction termination that is translating north beneath the central San Andreas Fault. Our results support the occurrence of localized lithospheric foundering beneath the high elevation eastern Sierra Nevada, where we find a lower crustal low Vs layer consistent with a small amount of partial melt. The high elevations relative to crust thickness and lower crustal low Vs zone are consistent with geological inferences that lithospheric foundering drove uplift and a ∼3–4 Ma pulse of basaltic magmatism.

Item Type:Article
Related URLs:
URLURL TypeDescription
Jiang, Chengxin0000-0002-8768-2782
Schmandt, Brandon0000-0003-1049-9020
Dougherty, Sara L.0000-0002-5327-3286
Clayton, Robert W.0000-0003-3323-3508
Lin, Fan-Chi0000-0003-0394-6830
Additional Information:© 2018 Elsevier B.V. Received 3 November 2017, Revised 2 February 2018, Accepted 6 February 2018, Available online 19 February 2018. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Seismic data from the CCSE array will be openly available through the IRIS Data Management Center starting in November 2017. Deployment of the CCSE array would not have been possible without the support of private landowners and the Kern and Tulare County Fire Departments who hosted seismographs. Richard Guy is thanked for coordinating much of the fieldwork effort. Most of the seismographs used in the project were provided by the Tectonics Observatory at Caltech, which was funded by the Gordon and Betty Moore Foundation. Emily Brodsky and Elizabeth Cochran are thanked for loaning additional instruments. Emily Wolin, Will Levandowski, and Carl Tape are thanked for constructive reviews. Data collection and analysis were supported by NSF EAR1315856 (BS), 1314910 (RWC), and CyberSEES-1442665 (FCL).
Group:Seismological Laboratory
Funding AgencyGrant Number
Gordon and Betty Moore FoundationUNSPECIFIED
Subject Keywords:Isabella Anomaly; San Andreas Fault; Sierra Nevada; Monterey microplate; lithospheric foundering
Record Number:CaltechAUTHORS:20180221-090936349
Persistent URL:
Official Citation:Chengxin Jiang, Brandon Schmandt, Steven M. Hansen, Sara L. Dougherty, Robert W. Clayton, Jamie Farrell, Fan-Chi Lin, Rayleigh and S wave tomography constraints on subduction termination and lithospheric foundering in central California, Earth and Planetary Science Letters, Volume 488, 15 April 2018, Pages 14-26, ISSN 0012-821X, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:84898
Deposited By: Tony Diaz
Deposited On:21 Feb 2018 17:55
Last Modified:15 Nov 2021 20:23

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