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Science 7 April 2000:
Vol. 288. no. 5463, pp. 122 - 125
DOI: 10.1126/science.288.5463.122
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Reports

Dilational Processes Accompanying Earthquakes in the Long Valley Caldera

Douglas S. Dreger, 1* Hrvoje Tkalčic, 1 Malcolm Johnston 2

Regional distance seismic moment tensor determinations and broadband waveforms of moment magnitude 4.6 to 4.9 earthquakes from a November 1997 Long Valley Caldera swarm, during an inflation episode, display evidence of anomalous seismic radiation characterized by non-double couple (NDC) moment tensors with significant volumetric components. Observed coseismic dilation suggests that hydrothermal or magmatic processes are directly triggering some of the seismicity in the region. Similarity in the NDC solutions implies a common source process, and the anomalous events may have been triggered by net fault-normal stress reduction due to high-pressure fluid injection or pressurization of fluid-saturated faults due to magmatic heating.

1 Berkeley Seismological Laboratory, University of California, Berkeley, CA 94720, USA.
2 U.S. Geological Survey, Menlo Park, CA 94025, USA.
*   To whom correspondence should be addressed at Berkeley Seismological Laboratory, 281 McCone Hall, University of California, Berkeley, CA 94720, USA. E-mail: dreger{at}seismo.berkeley.edu

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Moment Tensor Inversions of Icequakes on Gornergletscher, Switzerland.
F. Walter, J. F. Clinton, N. Deichmann, D. S. Dreger, S. E. Minson, and M. Funk (2009)
Bulletin of the Seismological Society of America 99, 852-870
   Abstract »    Full Text »    PDF »
Non-Double-Couple Earthquakes in the Long Valley Volcanic Region.
D. C. Templeton and D. S. Dreger (2006)
Bulletin of the Seismological Society of America 96, 69-79
   Abstract »    Full Text »    PDF »
Unrest in Long Valley Caldera, California, 1978-2004.
D. P. Hill (2006)
Geological Society, London, Special Publications 269, 1-24
   Abstract »    PDF »
Equivalent Volume Sources for Explosions at Depth: Theory and Observations.
P. G. Richards and W.-Y. Kim (2005)
Bulletin of the Seismological Society of America 95, 401-407
   Abstract »    Full Text »    PDF »
Source Parameters of Eastern California and Western Nevada Earthquakes from Regional Moment Tensor Inversion.
(2003)
Bulletin of the Seismological Society of America 93, 61-84
Feasibility of Real-Time Broadband Waveform Inversion for Simultaneous Moment Tensor and Centroid Location Determination.
(2002)
Bulletin of the Seismological Society of America 92, 739-750
Volume Change of Seismic Sources from Moment Tensors.
(2001)
Bulletin of the Seismological Society of America 91, 880-884
Observations of Earthquake Source Parameters at 2 km Depth in the Long Valley Caldera, Eastern California.
(2001)
Bulletin of the Seismological Society of America 91, 165-177


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Science. ISSN 0036-8075 (print), 1095-9203 (online)