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Evidence for Deep Magma Injection Beneath Lake Tahoe, Nevada-California

Smith, Kenneth D. and von Seggern, David and Blewitt, Geoffrey and Preston, Leiph and Anderson, John G. and Wernicke, Brian P. and Davis, James L. (2004) Evidence for Deep Magma Injection Beneath Lake Tahoe, Nevada-California. Science, 305 (5688). pp. 1277-1280. ISSN 0036-8075.

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A deep earthquake swarm in late 2003 at Lake Tahoe, California (Richter magnitude < 2.2; depth of 29 to 33 kilometers), was coeval with a transient displacement of 6 millimeters horizontally outward from the swarm and 8 millimeters upward measured at global positioning system station Slide Mountain (SLID) 18 kilometers to the northeast. During the first 23 days of the swarm, hypocentral depths migrated at a rate of 2.4 millimeters per second up-dip along a 40-square-kilometer structure striking north 30° west and dipping 50° to the northeast. SLID's transient velocity of 20 millimeters per year implies a lower bound of 200 nanostrains per year (parts per billion per year) on local strain rates, an order of magnitude greater than the 1996 to 2003 regional rate. The geodetic displacement is too large to be explained by the elastic strain from the cumulative seismic moment of the sequence, suggesting an aseismic forcing mechanism. Aspects of the swarm and SLID displacements are consistent with lower-crustal magma injection under Lake Tahoe.

Item Type:Article
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Wernicke, Brian P.0000-0002-7659-8358
Additional Information:© 2004 American Association for the Advancement of Science. Received 9 June 2004; accepted 28 July 2004. Published online 5 August 2004. The University of Nevada, Reno seismic network in northern Nevada is operated under the U.S. Geological Survey National Earthquake Hazards Reduction Program with support from the State of Nevada. The GPS data analysis was funded by the Department of Energy, Yucca Mountain Project. The BARGEN GPS network is funded by NSF and the Department of Energy, with operational support from UNAVCO, Inc. The GIPSY OASIS II software and global GPS data products were provided by the Jet Propulsion Laboratory. We thank G. Oppliger for a review of the manuscript and M. Coolbaugh for generating the regional strain map figure. Several stations in the Nevada K-12 seismic network, Storey County High School, Carson City High School, and Douglas County High School contributed phase arrival data for constraining earthquake locations in the lower-crustal swarm. We thank three anonymous reviewers for their time and effort in reviewing the manuscript.
Group:Caltech Tectonics Observatory
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Caltech Tectonics Observatory60
Issue or Number:5688
Record Number:CaltechAUTHORS:20101123-081625102
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Official Citation:Evidence for Deep Magma Injection Beneath Lake Tahoe, Nevada-California Kenneth D. Smith, * David von Seggern, * Geoffrey Blewitt, * Leiph Preston, * John G. Anderson, * Brian P. Wernicke, * and James L. Davis Science 27 August 2004: 305 (5688), 1277-1280.Published online 5 August 2004 [DOI:10.1126/science.1101304]
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:20966
Deposited By: Tony Diaz
Deposited On:07 Dec 2010 00:44
Last Modified:03 Oct 2019 02:17

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