GPS measurements and earthquake cycle modeling of the Mexico subduction zone

该项目将继续对地震危险的墨西哥俯冲带（MSZ）进行基于gps的长期研究，该地区板块收敛速度快，海沟靠近海岸，地震复发间隔短（50-100年），几乎是平坦的俯冲，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该地区的工作。所有在墨西哥大陆运营大量GPS站点的墨西哥调查人员已经同意合作进行MSZ地震周期的综合研究，这是第一次将整个1600公里长的MSZ的GPS观测数据整合在一起的研究，在MSZ，地震周期的所有阶段都被GPS记录了两次或两次以上。他们会用吉普赛语吗？新推出的单站模糊分辨功能和JPL？美国的新卫星产品（将于2011年年中推出）将重新处理来自&amp；#8764；80个连续电台和100多个竞选网站。台站坐标噪声的预期减少将使我们能够比以前更详细地研究偶发性瞬变滑动、震间应变和余震。研究人员将测试并应用一种新的逆过程来估计和分离震间弹性应变、幕式瞬变滑动、同震破裂、震后断层余震和震后粘弹性反弹对GPS站时间序列的贡献。关于瞬态滑动的平稳性和深度限制的具体假设将进行测试，粘弹性建模将进行，以了解目前墨西哥沿海和内陆地区的变形。在墨西哥西部的哈利斯科/科利马地区，1995年和2003年发生的大俯冲逆冲地震、由这些地震引发的断层余震以及最近发现的非火山地震为严格确定这三个过程在俯冲界面上的起源位置以及它们揭示的决定俯冲界面摩擦状态下倾变化的因素提供了一个绝佳的机会。来自MSZ的米却肯、格雷罗和瓦哈卡部分的GPS和地震数据将用于研究这两个地区的间歇性瞬变滑动在空间或时间上是如何连接的，以及这种滑动相对于这两个地区的发震带和非火山震颤发生在哪里。同样的数据将用于确定沿这些海沟段的地震间耦合分布，从而确定地震危险性。来自恰帕斯海沟段的GPS数据将用于测试那里的瞬态滑动，并估计地震间锁定的程度，以便更好地了解恰帕斯地震间隙的原因。与危险相关的有用产出将包括沿大多数地震易发MSZ的震间锁定率的估计，评估墨西哥南部的瞬态滑动是否加载或卸载了发震区的较低区域，以及对墨西哥Fuego de Colima火山及其周围的变形率的持续监测。美国最活跃的火山。对联阿援助团的分奖将使德梅茨及其墨西哥合作者建造的35个连续GPS站能够继续运作和维护，这些站占墨西哥的三分之一。美国的GPS基础设施。最后，该项目将资助2名威斯康星大学研究生。项目参与者将向学生、教师和墨西哥政府官员进行外展演讲。

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.