Refining Seismic Velocity and Attenuation Structure of the San Andreas Fault Near Parkfield, California Using Full-3D Waveform Tomography

University Of Wyoming, Laramie WY

Investigators

Abstract

The PI will conduct full-3D waveform tomography (F3DT) for the seismic velocity and attenuation structure on the San Andreas Fault zone around the Parkfield area in California. In the F3DT algorithm, both the reference structural model and the derived model perturbations are all 3D in space and the full-wave sensitivity (Fréchet) kernels are calculated from the full physics of 3D wave propagation. Joint inversions will be carried out for both seismic velocity and attenuation structures of the San Andreas Fault Zone using waveform recordings from natural and/or man-made earthquakes. By integrating high-quality waveform data into the F3DT algorithm, they expect to substantially enhance both the resolution and the accuracy of the 3D seismic velocity and attenuation structure in the Parkfield area. Variations in physical properties of a fault zone may influence the generation, propagation and arrest of large earthquakes. Results from previous studies suggest that inelastic processes such as migration of fluids in fractures or microcracks and the associated changes in pore pressure and chemical effects such as stress corrosion and pressure solution may lead to mechanical failure and nucleation of earthquakes. Since attenuation structure is sensitive to fracturing, crack accumulation and partial saturation, the proposed high-resolution full-3D waveform tomography for fault-zone attenuation structure will provide important additional constraints to improve our understanding of fault-zone processes. This project is funded jointly by the EPSCoR, Earthscope and Geophysics programs.