Paleostress and Mechanisms of Slip on the San Gabriel Fault,San Andreas Fault System, California

来自浅井的主应力方向数据表明，加州圣安德烈亚斯断层存在低震级剪切应力。这些数据与热流测量和预测一致，但与估计的岩石强度不一致。该项目将试图通过确定圣盖博断层活动期间存在的主应力的方向，来验证一个假设，即浅层井数据代表了地壳中部深处的应力状态，圣盖博断层现在已被深度挖掘出来。通过对断裂带构造的岩组构分析，可以确定古应力取向和滑动机制。结果将与实验室数据进行比较，并应用于断层强度明显较弱的问题。

Data on principal stress orientation from shallow wells indicate a low magnitude shear stress on the San Andreas Fault, California. These data are consistent with heat-flow measure- ments and predictions, but are inconsistent with estimated strength of rocks. This project will attempt to test the hypo- thesis that the shallow well data are representative of the state of stress at mid-crustal depths by determining the orien- tation of the principal stresses that existed during activity on the San Gabriel fault, now deeply exhumed. Paleostress orien- tations and mechanisms of slip will be determined by petrofabric analysis of structures in the fault zone. Results will be compared to laboratory data and applied to the problem of the apparently weak fault strength.