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

PI将对加州帕克菲尔德地区周围的圣安德烈亚斯断层带的地震速度和衰减结构进行全三维波形层析成像（F3 DT）。在F3 DT算法中，参考结构模型和衍生模型扰动都是空间上的3D，并且全波灵敏度（Fréchet）核是从3D波传播的完整物理学计算的。将利用自然和/或人为地震的波形记录，对圣安德烈亚斯断层带的地震速度和衰减结构进行联合反演。通过将高质量的波形数据集成到F3 DT算法中，他们期望大幅提高帕克菲尔德地区三维地震速度和衰减结构的分辨率和精度。断层带物理性质的变化可能会影响大地震的产生，传播和停止。以往的研究结果表明，非弹性过程，如流体在裂缝或微裂缝中的迁移和相关的孔隙压力的变化和化学效应，如应力腐蚀和压力溶解可能会导致机械故障和地震成核。由于衰减结构是敏感的压裂，裂缝积累和部分饱和，建议高分辨率全三维波形层析成像断层带衰减结构将提供重要的额外的约束，以提高我们的理解断层带processes.This项目是由EPSCoR，Earthscope和地球物理计划联合资助。

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.