INVERSION FOR P-WAVE AND S-WAVE ATTENUATION STRUCTURE, LONG VALLEY CALDERA, CALIFORNIA

被引:32
作者
PONKO, SC
SANDERS, CO
机构
关键词
D O I
10.1029/93JB03405
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
P and S wave amplitude data from digital, three-component seismograms of local earthquakes recorded on a temporary seismic array have been used to tomographically invert for the three-dimensional attenuation structure in the upper crust of Long Valley caldera, California. Differential attenuation (partial derivative Q-1) values are obtained through the use of a spectral ratio technique that minimizes the site effect on the spectral ratios. The spectral ratios are inverted for partial derivative Q-1 using the LSQR algorithm. Zones of high, positive P wave partial derivative Q-1 (greater P wave attenuation) are observed at a depth of 4-5 km beneath the east flank of Mammoth Mountain and at 6-8 km beneath the southwestern edge of the resurgent dome. A region of positive S wave partial derivative Q-1 is seen at 7-8 km beneath the southern edge of the resurgent dome, whereas at 6-7 km, the S wave results are near average. The region of positive S wave partial derivative Q-1 at 7-8 km beneath the resurgent dome may indicate the roof of a magmatic system. The positive P wave partial derivative Q-1 at 4-5 km beneath Mammoth Mountain and 6-8 km beneath the resurgent dome may be due to the presence of a compressible fluid such as supercritical water. These zones may represent some of the source regions for the Long Valley geothermal system.
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页码:2619 / 2635
页数:17
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