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.

该项目将继续对具有地震危险的墨西哥俯冲带 (MSZ) 进行基于 GPS 的长期研究，该区域快速的板块收敛速度、海沟与海岸的接近、地震复发间隔短（50-100 年）以及几乎平坦的俯冲带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之前在该地区的工作。在墨西哥大陆运营大量 GPS 站的所有墨西哥调查人员都同意合作开展 MSZ 地震周期的综合研究，这使得这是第一项整合整个 1600 公里长的 MSZ 的 GPS 观测结果的研究，其中地震周期的所有阶段都已被 GPS 记录了两次或多次。他们将使用 GIPSY 新推出的单站模糊度解决功能和 JPL 的新卫星产品（将于 2011 年中期推出）来重新处理来自 80 个连续站和 100 多个活动站点的汇总 GPS 数据。台站坐标噪声的预期降低将允许比以前更详细地研究偶发瞬态滑移、震间应变和后滑。研究人员将测试并应用一种新的逆过程来估计和隔离震间弹性应变、情景瞬态滑移、同震破裂、震后断层后滑和震后粘弹性回弹对 GPS 站时间序列的贡献。将测试有关瞬态滑移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震颤为严格确定这三个过程沿俯冲界面的起源以及它们揭示的决定沿俯冲界面摩擦状态下倾变化的因素提供了一个特殊的机会。来自 MSZ 米却肯州、格雷罗州和瓦哈卡州段的 GPS 和地震数据将用于研究这两个地区的阵发性瞬态滑移在空间或时间上如何以及是否存在关联，以及这种滑移相对于这两个地区的地震带和非火山地震发生的位置。相同的数据将用于确定震间耦合的分布，从而确定这些沟槽段的地震危险性。来自恰帕斯海沟段的 GPS 数据将用于测试那里的瞬态滑动并估计震间锁定程度，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对大部分地震多发 MSZ 沿线的震间锁定率的估计、对墨西哥南部瞬态滑移是否对地震发生区较低区域施加载荷或卸载的评估，以及对墨西哥最活跃的火山 Fuego de Colima 及其周围变形率的持续监测。授予 UNAVCO 的子合同将使 DeMets 及其墨西哥合作者建造的 35 个连续 GPS 站能够继续运行和维护，这些站构成了墨西哥 GPS 基础设施的三分之一。最后，该项目将资助 2 名华盛顿大学研究生。项目参与者将向学生、教师和墨西哥政府官员进行外展演示。