Electromagnetic Imaging of Fluids in the San Andreas Fault: Collaborative Research with University of Washington and Oregon State University

9614411埃格伯特这是俄勒冈州立大学和华盛顿大学的合作项目，目的是获取和解释圣安德烈亚斯断层(SAF)两段的高分辨率大地电磁(MT)数据。在以前的工作中，P.I.利用连续的大地电磁剖面数据，获得了帕克菲尔德段深达4公里的高分辨率电阻率图像，揭示了断层核心的一条异常低电阻率的狭窄地带。在该项目的第一阶段，他们将继续在帕克菲尔德工作，收集靠近中山的圣安德烈亚斯断层的更多剖面，以获得该地区电阻率的三维图像。为了将图像延伸到地震孕育深度，他们将在距离断层20公里的地方获取MT数据，并将采用受控震源勘探方法。在第二阶段，将在加利福尼亚州霍利斯特附近对圣安德烈亚斯断层中央爬行段进行三维高分辨率调查。由于地壳岩石的电阻率在很大程度上受流体含量的控制，这些测量将允许对断裂带内流体的分布和连通性施加限制，并表明这些特性在具有不同力学行为的区段之间存在差异。这些结果有望最终提供有关流体在地震过程中所起作用的重要信息。***

9614411 Egbert This is a collaborative project between Oregon State University and the University of Washington to acquire and interpret high resolution magnetotelluric (MT) data across two segments of the San Andreas Fault (SAF). In previous work the P.Is. have used continuous MT profiling data to obtain high resolution images of electrical resistivity to depths of 4 km across the Parkfield segment, revealing a narrow zone of anomalously low resistivity in the core of the fault. In the first phase of this project, they will continue work at Parkfield, collecting additional profiles across the San Andreas Fault near Middle Mountain, to obtain a three-dimensional image of electrical resistivity in this area. To extend the image to seismogenic depths they will take MT data at distances of up to 20 km from the fault, and will employ controlled source exploration methods. In the second phase, a three-dimensional high resolution survey of the central creeping segment of the San Andreas fault will be conducted near Hollister, California. Because the resistivity of crustal rocks is largely controlled by fluid content, these surveys will allow constraints to be placed on the distribution and connectivity of fluids within the fault zone, and to show hmw these properties vary between segments with different mechanical behaviors. These results are expected to ultimately provide important information on the role of fluids in the earthquake process. ***