HR: 1330h
AN: V52B-0439    [PDF]
TI: Fluid Influenced Faulting in the Long Valley Volcanic Region
AU: * Templeton, D C
EM: dennise@seismo.berkeley.edu
AF: Berkeley Seismological Laboratory, University of California, Berkeley, 215 McCone Hall, Berkeley, CA 94720-4760 United States
AU: Dreger, D
EM: dreger@seismo.berkeley.edu
AF: Berkeley Seismological Laboratory, University of California, Berkeley, 215 McCone Hall, Berkeley, CA 94720-4760 United States
AB: To better understand how hydrothermal and magmatic systems directly influence local earthquake production, we determined the extent of fluid influenced faulting in the Long Valley volcanic region. We focused on a 100 km wide circular area centered at Long Valley caldera which also encompassed the Mono-Inyo Craters to the north and the seismically active Sierra Nevada mountain block to the south. We comprehensively searched for events since 1993 with coseismic volume changes in their source regions by solving for the full moment tensor solution which includes an isotropic (volumetric) component. We use a nested F test statistic to compare this solution with the deviatoric solution, which assumes no volume change, to determine the probability that the additional volumetric component represents a true aspect of the source mechanism rather than being simply an added non-physical parameter in the inversion. Moment tensor solutions were computed from regional broadband Berkeley Digital Seismic Network data for events greater than M3.5. This investigation showed that fluid influenced earthquakes are fairly unique in this region. They occur only in the south moat of the caldera, where there has been extensive independent evidence of magma movement, and in the Sierra Nevada block, where there has been equivocal evidence of magma existence (Hough et al., 2000; Peppin et al., 1989).
UR: http://www.seismo.berkeley.edu/~dennise/fdes.html
DE: 7280 Volcano seismology (8419)
DE: 8400 VOLCANOLOGY
DE: 8424 Hydrothermal systems (8135)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting