Bimaterial Interfaces, Damage Zones, Earthquake Directivities and Signatures of Rupture Opening in the Parkfield Section of the San Andreas Fault

研究重点是系统的高分辨率成像的双材料界面，低速断层带层，地震的破裂方向性，和地震信号的开放破裂模式沿着不同的故障段的圣安德烈亚斯断层系统在帕克菲尔德地区。总的目标是提供多信号测试，基于大地震波形和目录数据集，为假设，即大的走滑断层上的地震具有由跨断层的速度对比控制的优选传播方向，并为这样的断层上的地震破裂具有断层的拉伸分量的可能性。双材料界面成像采用断层带首波，其沿着双材料断层和直接P波交替作用。断层带首波提供了尖锐的双材料界面存在的最诊断信号和最高分辨率的工具，在深度成像的地震属性。断层带陷波被用来量化对称属性相对于主破裂面和其他特征的受损断层带层在不同的位置。破裂方向性的分析包括在每个事件的相反的沿走向方向上叠加余震率，并在不同的时空尺度上观察叠加数据的动态触发模式的对称性。开放式破裂模式的检查利用了最近的理论计算所建议的几个潜在的地震信号。这些研究还侧重于阐明SAFOD场地周围的构造和地震性质，阐明1966年和2004年M6事件震源之间的主要SAF的性质，并阐明主要SAF与西南断裂带之间的连通性。这些研究可以对地震和断层力学的关键方面产生深远的影响，包括有效本构律，震源和破裂性质，产生的摩擦热，断层之间的相互作用等。这些分析有助于解决现有的争议。地震传播方向的统计偏好的积极结果可能会导致主要断层附近的地震震动危险性的精确估计。

The studies focus on systematic high-resolution imaging of bimaterial interfaces, low velocity fault zone layers, rupture directivities of earthquakes, and seismic signatures of opening rupture mode along various fault segments of the San Andreas Fault system in the Parkfield area. The overall goal is to provide multi-signal tests, based on large seismic waveform and catalog data sets, for the hypothesis that earthquakes on large strike-slip faults have preferred propagation directions that are controlled by the velocity contrasts across the faults, and for the possibility that earthquake ruptures on such faults have tensile component of faulting. The imaging of bimaterial interfaces employ fault zone head waves that refract along bimaterial faults and direct P waves. The fault zone head waves provide the most diagnostic signal for the existence of sharp bimaterial interfaces and the highest-resolution tool for imaging their seismic properties at depth. Fault zone trapped waves are used to quantify symmetry properties with respect to the main rupture surface and other characteristics of damaged fault zone layers at different locations. The analysis of rupture directivities involves stacking aftershock rates at the opposite along-strike directions of each event and observing symmetry properties of dynamic triggering patterns of the stacked data at different space-time scales. The examination for opening rupture mode utilizes several potential seismic signals that are suggested by recent theoretical calculations. The studies also focus on clarifying the structural and earthquake properties around the SAFOD site, clarifying properties of the main SAF between the hypocenters of the 1966 and 2004 M6 events, and clarifying the connectivity between the main SAF and the Southwest Fracture zone at depth. The studies can have profound implications for key aspects of earthquake and fault mechanics including effective constitutive laws, earthquake source and rupture properties, generated frictional heat, interaction between faults and more. The analyses can help resolving existing controversies. Positive results on statistical preference of earthquake propagation directions may lead to refined estimates of seismic shaking hazard near major faults.