Publication Date:
2004-08-07
Description:
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 degrees west and dipping 50 degrees 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.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Smith, Kenneth D -- von Seggern, David -- Blewitt, Geoffrey -- Preston, Leiph -- Anderson, John G -- Wernicke, Brian P -- Davis, James L -- New York, N.Y. -- Science. 2004 Aug 27;305(5688):1277-80. Epub 2004 Aug 5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Nevada Seismological Laboratory, University of Nevada, Reno, NV 89557, USA. ken@seismo.unr.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/15297623" target="_blank"〉PubMed〈/a〉
Print ISSN:
0036-8075
Electronic ISSN:
1095-9203
Topics:
Biology
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Chemistry and Pharmacology
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Computer Science
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Medicine
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Natural Sciences in General
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Physics
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