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SEMINAR: GEOTOPICS - Monday (4/12) 3.15PM - Dr. Guoqing LIN (RSMAS-MGG)

From: Marco Bagnardi <mbagnardi@rsmas.miami.edu>
Subject: SEMINAR: GEOTOPICS - Monday (4/12) 3.15PM - Dr. Guoqing LIN (RSMAS-MGG)
Date: Wed, 7 Apr 2010 14:04:06 -0400

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3:15 PM, Monday, April 12th, 2010
SLAB Seminar Room, S/A 103
Refreshments 3:00 PM


Dr. Guoqing LIN
Assistant Professor - RSMAS - MGG

 
"Evidence for water-filled cracks in earthquake source regions from seismic tomography and high-resolution Vp/Vs estimates"

Abstract:

"We identify lowered Vp/Vs ratios near earthquake source regions in southern California using observations from a seismic tomography model and high-resolution local Vp/Vs estimates using waveform cross-correlation data from within similar event clusters. The median tomographic Vp/Vs ratio is 1.716±0.008 at all the relocated crustal earthquake locations, which is less than the background median value of 1.729±0.007 for the tomography model at all locations. The median in situ Vp/Vs ratio of 1.673±0.022 within the similar event clusters suggests that tomographic studies are underestimating the true Vp/Vs anomalies at source regions. Interpretation of Vp/Vs anomalies is complicated by the scatter in values obtained for individual clusters and in comparisons to absolute Vp and Vs velocities in the tomography model. However, the low Vp/Vs ratios measured for the seismicity clusters are hard to explain with known rocks and suggest the presence of water-filled cracks with several percent porosity in earthquake source regions in southern California, which likely has an effect on faulting and earthquake activity."


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