Anomalous shear wave attenuation in the shallow crust beneath the Coso volcanic region, California

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Journal Article: Anomalous shear wave attenuation in the shallow crust beneath the Coso volcanic region, California

Abstract
We use seismograms of local earthquakes to image relative shear wave attenuation structure in the shallow crust beneath the region containing the Coso volcanic-geothermal area of eastern California. SV and P wave amplitudes were measured from vertical component seismograms of earthquakes that occurred in the Coso-southern Sierra Nevada region from July 1983 to 1985. Seismograms of 16 small earthquakes show SV amplitudes which are greatly diminished at some azimuths and takeoff angles, indicating strong lateral variations in S wave attenuation in the area. Three-dimensional images of the relative S wave attenuation structure are obtained from forward modeling and a back projection inversion of the amplitude data. The results indicate regions within a 20 by 30 by 10 km volume of the shallow crust (one shallower than 5 km) that severely attenuate SV waves passing through them. These anomalies lie beneath the Indian Wells Valley 30 km south of the Coso volcanic field, and are coincident with the epicentral locations of recent earthquake swarms. No anomalous attenuation is seen beneath the Coso volcanic field above about 5 km depth. Geologic relations and the coincidence of anomalous slow P wave velocities suggest that the attenuation anomalies may be related to magmatism along the eastern Sierra front.

Authors 
Sanders, C.; Ho-Liu, P.; Rinn, D.; Kanamori and H.  








Published Journal 
Journal of Geophysical Research, 4/10/1988





DOI 
Not Provided
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Citation

Sanders, C.; Ho-Liu, P.; Rinn, D.; Kanamori, H.  . 4/10/1988. Anomalous shear wave attenuation in the shallow crust beneath the Coso volcanic region, California. Journal of Geophysical Research. (!) .


Related Geothermal Exploration Activities
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  1. Coso Geothermal Area
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