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

Abstract

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.