Earth and Planetary Science
EPS Near-Surface Geochemistry and Geobiology

Subsurface structure of Long Valley Caldera imaged with seismic scattering and intrinsic attenuation

Thursday, July 19, 2018

Imaging seismic intrinsic and scattering attenuation in Long Valley Caldera, California, by analyzing more than 1700 vertical‐component waveforms from local earthquakes. Observed energy envelopes are fit to the diffusion model and seismic attenuation images are produced using two‐dimensional space‐weighting functions. Low‐intrinsic and low‐scattering attenuation anomalies in the center‐south of the caldera correspond to the location of an earthquake swarm in 2014. We identify high‐intrinsic and high‐scattering attenuation anomalies in the fluid‐rich western and eastern areas of the caldera. From a comparison with other geophysical images (magnetotellurics, seismic tomography) we attribute these anomalies to a hydrothermal system (high attenuation). Average to high attenuation values are also observed at the adjacent Mammoth Mountain (south‐west of the caldera), and may also have a hydrothermal origin. High intrinsic attenuation at low frequencies to the west of the Hartley Springs Fault may be produced by the magmatic system that produced the Inyo craters. Seismic attenuation imaging provides insights into subsurface structures that are complementary to velocity and conductivity images.


J. PrudencioM. Manga, T. Taira



First published: 28 June 2018