S wave attenuation structure in Long Valley Caldera, California, from three‐component S‐to‐P amplitude ratio data

Using S-to-P amplitude ratios measured from three-component seismograms we tomographically imaged spatial variations in S wave attenuation in parts of Long Valley caldera. Data from seismograms of local earthquakes in the Long Valley caldera region that occurred during 1984 were employed with the S-to-P amplitude ratio technique with corrections for source radiation pattern to determine Q s . Resolution is limited throughout most of the model ; however, significant resolution and acceptable error in parts of the model allow meaningful interpretation of the results. The primary result is the image of a low-Q s anomaly at 7-8 km depth beneath the resurgent dome. This is independent evidence for high temperatures and possible magma accumulation at this location. Other regions of anomalously low Q s are marginally significant or poorly resolved ; of these low Q s at 4-5 km depth beneath the Inyo Domes has the most potential significance. The similarity of the results from the three-component data and from the vertical-component data implies that vertical-component data, which are generally more abundant, can be used with confidence.