Poster Presentation

We study the near-surface fault zone structure from ambient seismic noise data. The amplitude of the seismic wavefield contains information on seismic attenuation, which is sensitive to fault damage zone characterized by well-developed fractures within the fault zone, and possibly fluids. We extract amplitude decay information with uncertainty from the noise interferometry functions of seismic data recorded by a dense linear array of 65 3-C sensors across the San Jacinto Fault Zone at the Ramona reservation north of Anza, California. Then we invert for attenuation structure based on the linear station-triplet method (Liu et al. 2015; Allmark et al. 2018) for both Love and Rayleigh waves. The attenuation tomography results show strong attenuation (low Q values) correlated with known San Jacinto Fault surface traces and damage zone structure. The results also suggest radial anisotropy of shear attenuation, which is possibly due to the distinct sensitivity of SH and SV modes to different fracture orientations.