GPS measurements and earthquake cycle modeling of the Mexico subduction zone

该项目将继续对具有地震危险性的墨西哥俯冲带（MSZ）进行长期的基于GPS的研究，该俯冲带的快速板块会聚速率、海沟与海岸的接近、地震复发间隔短（#8776;50-100年）以及几乎平坦的俯冲为测量和模拟俯冲地震周期的所有阶段提供了绝佳的机会。拟议的工作在几个重要方面超越了他们以前在这一区域的工作。在墨西哥大陆操作大量GPS台站的所有墨西哥调查人员已同意合作对MSZ地震周期进行综合研究，这是第一次将整个1600公里长的MSZ的GPS观测结果进行综合研究，其中地震周期的所有阶段都被GPS记录了两次或多次。他们会用吉普赛人吗？的新推出的单站模糊分辨率功能和喷气推进实验室？该公司的新卫星产品（预计在2011年中期），以重新处理汇集的全球定位系统数据，从80个连续站和100多个活动的网站。预期减少站坐标噪声将允许更详细的研究幕瞬态滑动，震间应变，和后滑比以前可能的。研究人员将测试和应用一种新的逆过程来估计和隔离地震间弹性应变，幕式瞬时滑动，同震破裂，震后断层后滑和震后粘弹性反弹对GPS站时间序列的贡献。将测试有关瞬态滑动的平稳性和深度限制的具体假设，并进行粘弹性建模，以了解墨西哥沿海和内陆地区目前的变形。在墨西哥西部的哈利斯科/科利马地区，1995年和2003年发生的大型俯冲逆冲地震、由这些地震引发的断层后滑以及最近发现的非火山性震颤提供了一个难得的机会，可以严格确定这三个过程沿着俯冲界面的起源位置，以及它们揭示的决定俯冲界面沿着摩擦状态下倾变化的因素。GPS和地震数据从米霍坎，格雷罗，和瓦哈卡段的MSZ将被用来研究如何以及是否在两个地区的幕式瞬态滑动连接在空间或时间，以及这种滑动发生相对于地震孕震区和非火山震颤在这两个地区。同样的数据将用于确定地震间耦合的分布，从而确定沿着这些海沟段的地震危险性。来自恰帕斯海沟段的GPS数据将用于测试那里的瞬时滑动，并估计震间锁定的程度，以更好地了解恰帕斯地震间隙的原因。与灾害相关的有用输出将包括沿着大部分地震多发MSZ的震间锁定率估计，墨西哥南部的瞬时滑动是否加载或卸载孕震区的较低区域的评估，以及对墨西哥火地岛及其周围的变形率的连续监测？这是最活跃的火山。向联合国志愿人员组织提供的次级赠款将使DeMets和他的墨西哥合作者建造的35个连续的全球定位系统站能够继续运行和维护，这些站占墨西哥的三分之一。的GPS基础设施。最后，该项目将资助2名UW研究生。项目参与者将向学生、教师和墨西哥政府官员进行外联介绍。

This project will continue a long-term GPS-based study of the seismically hazardous Mexico subduction zone (MSZ), where rapid plate convergence rates, the proximity of the trench to the coast, short earthquake recurrence intervals (≈50-100 years), and nearly flat subduction afford exceptional opportunities to measure and model all phases of the subduction earthquake cycle. The proposed work moves beyond their previous work in this region in several important respects. All theMexican investigators who operate significant numbers of GPS stations in mainland Mexico have agreed to collaborate on an integrated study of the MSZ earthquake cycle, making this the first study to integrate GPS observations from the entire 1600-km-long MSZ, where all phases of the earthquake cycle have been recorded two or more times by GPS. They will use GIPSY?s newly available single-station ambiguity-resolution feature and JPL?s new satellite products (due in mid-2011) to reprocess the pooled GPS data from ∼80 continuous stations and more than 100 campaign sites. The expected reductions in the station coordinate noise will permit more detailed studies of episodic transient slip, interseismic strain, and afterslip than were previously possible. The researchers will test and apply a new inverse procedure to estimate and isolate the contributions of interseismic elastic strain, episodic transient slip, coseismic rupture, postseismic fault afterslip, and postseismic viscoelastic rebound to GPS station time series. Specific hypotheses regarding the stationarity and depth limits of transient slip will be tested and viscoelastic modeling will be done to understand present deformation in coastal and interior areas of Mexico. In the Jalisco/Colima region of western Mexico, large subduction thrust earthquakes in 1995 and 2003, fault afterslip triggered by those earthquakes, and recently discovered nonvolcanic tremor offer an exceptional opportunity to determine rigorously where these three processes originate along the subduction interface and what they reveal about the factors that determine downdip changes in the frictional state along a subduction interface. GPS and seismic data from the Michoacan, Guerrero, and Oaxaca segments of the MSZ will be used to study how and whether episodic transient slip in the two regions is connected in space or time, and where this slip occurs relative to the seismogenic zones and nonvolcanic tremor in both regions. The same data will be used to determine the distribution of interseismic coupling and hence seismic hazard along these trench segments. GPS data from the Chiapas trench segment will be used to test for transient slip there and estimate the degree of interseismic locking, toward a better understanding of the cause of the Chiapas seismic gap. Useful output related to hazards will include estimates of interseismic locking rates along most of the earthquake-prone MSZ, assessment of whether transient slip in southern Mexico loads or unloads lower areas of the seismogenic zone, and continuous monitoring of deformation rates on and around Volcan Fuego de Colima, Mexico?s most active volcano. A sub-award to UNAVCO will enable the continued operation and maintenance of the 35 continuous GPS stations built by DeMets and hisMexican collaborators, which constitute one-third of Mexico?s GPS infrastructure. Finally, the project will fund 2 UW graduate students. Outreach presentations to students, faculty, and Mexican government officials will be done by the project participants.