Seismological evidence for magmatic and hydrothermal structure in Long Valley Caldera from local earthquake attenuation and velocity tomography

We compare the results of six different tomographic inversions for the three‐dimensional seismic attenuation and velocity structure in Long Valley caldera, California, in order to constrain interpretations on the location and character of magmatic and geothermal structure in the caldera crust. P and S wave amplitudes and arrival times obtained in previous studies from seismograms of local earthquakes recorded on vertical‐ and three‐component seismographs were inverted for Q SV −1 , Q SH −1 , Δ Q S −1 , Δ Q P −1 , and Δ V P / V S in the upper 9 km of the caldera crust. Detailed comparisons of the results of the inversions suggest significant locations of high temperatures and perhaps magma and hydrothermal zones in the caldera. A region of low Q s with locally variable Q P and V P / V S is imaged in the 7–9 km depth range beneath the resurgent dome. Overlying and adjacent to this anomaly are significant low‐ Q P and low‐ V P / V S anomalies as well as smaller zones of low Q S and high V P / V S . Together, these suggest zones of high temperature/magma below and adjacent to zones of supercritical hydrothermal fluids. At 4–5 km depth along the southern rim of the caldera just east of Mammoth Mountain a significant anomaly with relatively low‐ Q P and relatively low‐ V P / V S is imaged and is interpreted as a supercritical hydrothermal zone. Poorly resolved relatively low Q P and relatively high V P / V S are seen at 4–5 km depth beneath the Inyo craters, suggesting possible high temperatures and perhaps magma. Because of lack of data in the individual inversions the resultant images have spatially variable error and resolution. However, by comparing multiple images of different seismic parameters we have improved our ability to determine the significance of and constrain interpretation of seismic structure anomalies.