Transient Deformation in Guerrero, Mexico

本研究结合大地测量学、地震学和数值模型来阐明地震瞬变的起源和性质，以及它们对墨西哥格雷罗州和其他俯冲带地震危险性的影响。研究区域包括了大约200公里的可可斯-北美板块边界段。西北地区最后一次大地震发生在1911年。据估计，如果格雷罗断层破裂，其震级将超过8兆瓦。GPS测量对于确定俯冲带中地震（瞬态）滑动事件的广泛存在至关重要。最近，地震震颤研究已与地震滑动事件联系起来。地震资料对瞬变的定位和传播具有更高的分辨率，而GPS继续限制它们的矩释放。需要大地测量学和地震学来了解瞬变的来源和周期性，以及它们与整个地震周期中俯冲过程的机制之间的关系。科罗拉多大学于1997年开始格雷罗GPS项目，以测量/模拟该地区的地壳变形率并评估地震危险性。墨西哥国立自治大学（UNAM）的教师和学生从一开始就是这个项目的合作伙伴。此次合作的结果是，目前格雷罗州有10台GPS接收器在运行。利用这些连续的GPS装置和早期的竞选数据，已经证明在过去十年中格雷罗州发生了三次非常大的瞬变。pi打算改进和维护GPS仪器，改进和分发位置估计，并对GPS数据建模。在这个项目期间，加州理工学院和墨西哥国立自治大学将在格雷罗收集宽带地震数据，有可能进行地震检测。与哈佛大学一个小组的合作将允许将大地测量和地震观测与三维数值模型进行比较，其中包括温度依赖性、速率和状态摩擦以及孔隙压力效应。

This study combines geodesy, seismology, and numerical models to elucidate the origin and nature of aseismic transients and their impact on seismic hazard in the Mexican state of Guerrero and in other subduction zones. The study area encompasses a ~200 km segment of the Cocos-North America plate boundary. The last great earthquake in the northwest section of region occurred in 1911. It has been estimated that if the Guerrero gap were to rupture, its magnitude would exceed Mw 8. GPS measurements have been critical in establishing the widespread existence of aseismic (transient) slip events in subduction zones. More recently, seismic tremor studies have been correlated with aseismic slip events. The seismic data have greater resolution of the location and propagation of transients, while GPS continues to constrain their moment release. Both geodesy and seismology will be needed to understand the source and periodicity of transients and how they relate to the mechanics of the subduction process throughout the earthquake cycle.CU began the Guerrero GPS project in 1997 to measure/model crustal deformation rates and assess seismic hazard in the region. The National Autonomous University of Mexico (UNAM) faculty and students have been partners in this project since its inception. There are currently 10 GPS receivers operating in Guerrero as the result of this collaboration. Using these continuous GPS installations and earlier campaign data it has been demonstrated that three very large transients have occurred in Guerrero in the last decade. The PIs intend to improve and maintain GPS instrumentation, improve and distribute position estimates, and model the GPS data. Broadband seismic data will be collected in Guerrero by Caltech and UNAM during this project period, potentially allowing for tremor detection. A collaboration with a group at Harvard will allow comparison of geodetic and seismic observations with three-dimensional numerical models that includes temperature dependence, rate and state friction, and pore pressure effects.