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Evidence for strong lateral seismic velocity variation in the lower crust and upper mantle beneath the California margin

Lai, Voon Hui and Graves, Robert W. and Wei, Shengji and Helmberger, Don (2017) Evidence for strong lateral seismic velocity variation in the lower crust and upper mantle beneath the California margin. Earth and Planetary Science Letters, 463 . pp. 202-211. ISSN 0012-821X. http://resolver.caltech.edu/CaltechAUTHORS:20170303-085007254

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Abstract

Regional seismograms from earthquakes in Northern California show a systematic difference in arrival times across Southern California where long period (30–50 s) SH waves arrive up to 15 s earlier at stations near the coast compared with sites towards the east at similar epicentral distances. We attribute this time difference to heterogeneity of the velocity structure at the crust–mantle interface beneath the California margin. To model these observations, we propose a fast seismic layer, with thickness growing westward from the San Andreas along with a thicker and slower continental crust to the east. Synthetics generated from such a model are able to match the observed timing of SH waveforms better than existing 3D models. The presence of a strong upper mantle buttressed against a weaker crust has a major influence in how the boundary between the Pacific plate and North American plate deforms and may explain the observed asymmetric strain rate across the boundary.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1016/j.epsl.2017.02.002DOIArticle
http://www.sciencedirect.com/science/article/pii/S0012821X17300626PublisherArticle
Additional Information:© 2017 Elsevier B.V. Received 19 October 2016; Received in revised form 31 January 2017; Accepted 1 February 2017. This work is supported by USGS Earthquake Hazards Program award G15AP00029 along with partial support from NSF-Earthscope program, EAR-1358646 and USGS Cooperative Agreement G14AC00109. Constructive reviews provided by Brad Aagaard, Annemarie Baltay, Carl Tape and an anonymous reviewer were very helpful in improving the manuscript. Waveform data for this study were accessed through the Northern California Earthquake Data Center (NCEDC), http://dx.doi.org/10.7932/NCEDC, and Southern California Earthquake Data Center (SCEDC) at Caltech, http://dx.doi.org/10.7909/C3WD3xH1. Maps were created using General Mapping Tools (GMT) software (Wessel et al., 2013).
Group:Seismological Laboratory
Funders:
Funding AgencyGrant Number
USGSG15AP00029
NSFEAR-1358646
USGSG14AC00109
Subject Keywords:waveform modeling; lithosphere; California; plate boundary; velocity structure; San Andreas fault
Record Number:CaltechAUTHORS:20170303-085007254
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20170303-085007254
Official Citation:Voon Hui Lai, Robert W. Graves, Shengji Wei, Don Helmberger, Evidence for strong lateral seismic velocity variation in the lower crust and upper mantle beneath the California margin, Earth and Planetary Science Letters, Volume 463, 1 April 2017, Pages 202-211, ISSN 0012-821X, http://dx.doi.org/10.1016/j.epsl.2017.02.002. (http://www.sciencedirect.com/science/article/pii/S0012821X17300626)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:74683
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:10 Mar 2017 15:53
Last Modified:10 Mar 2017 15:53

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