GPS measurements and earthquake cycle modeling of the Mexico subduction zone

墨西哥俯冲带的 GPS 测量和地震周期建模

• 批准号: 1114174
• 负责人: Dennis DeMets
• 金额: $ 53.99万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-08-01 至 2017-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1114174&HistoricalAwards=false
• 关键词: GPS; measurements; earthquake; cycle; modeling

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.

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，在那里，快速的板块会聚速度、海沟靠近海岸、地震重复间隔短(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该区域的工作。所有在墨西哥大陆运营着大量GPS观测站的墨西哥调查人员已经同意合作对MSZ地震周期进行综合研究，这使这项研究成为第一个整合整个1600公里长的MSZ地震周期GPS观测的研究，在那里，GPS已经记录了地震周期的所有阶段两次或更多次。他们将使用新推出的吉普赛？S单站模糊解算功能和喷气推进实验室？S的新卫星产品(定于2011年年中)，重新处理从80个连续站和100多个活动地点收集的GPS数据。台站坐标噪声的预期降低将使对幕式瞬时滑动、震间应变和余滑的更详细的研究成为可能。研究人员将测试和应用一种新的反演程序，以估计和分离地震间弹性应变、幕式瞬时滑动、同震破裂、震后断层余滑和震后粘弹性反弹对GPS站时间序列的贡献。将测试有关瞬时滑动的平稳性和深度极限的具体假设，并将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年发生的大型俯冲推覆地震、由这些地震引发的断层余滑以及最近发现的非火山地震为严格确定这三个过程沿俯冲界面起源的位置以及它们揭示了决定俯冲界面摩擦状态下倾变化的因素提供了一个难得的机会。来自MSZ的Michoacan、Guerrero和Oaxaca段的GPS和地震数据将被用来研究这两个地区的幕式瞬时滑动如何以及是否在空间或时间上联系在一起，以及相对于两个地区的孕震带和非火山震动发生在哪里。同样的数据将被用来确定地震间耦合的分布，从而确定这些海沟段的地震危险。来自恰帕斯海沟段的GPS数据将用于测试那里的瞬时滑动，并估计地震间锁定的程度，以更好地了解恰帕斯地震空区的原因。与灾害有关的有用输出将包括沿大多数地震多发的MSZ的地震间锁定率的估计，墨西哥南部的瞬时滑动是否加载或卸载了地震孕育区的较低区域的评估，以及对墨西哥福戈德科利马火山及其周围变形速率的持续监测？S是最活跃的火山。授予UNAVCO的分包将使德梅茨和他的墨西哥合作者建造的35个连续GPS站得以继续运营和维护，这些站构成了墨西哥S全球定位系统基础设施的三分之一。最后，该项目将资助两名密歇根大学的研究生。项目参与者将向学生、教职员工和墨西哥政府官员进行外展演示。