Collaborative research: A better understanding of seismic hazard in Tehuantepec, Mexico, using amphibious MT studies

合作研究：利用两栖 MT 研究更好地了解墨西哥特万特佩克的地震灾害

• 批准号: 2105776
• 负责人: Steven Constable
• 金额: $ 45.3万
• 依托单位: University of California-San Diego Scripps Inst of Oceanography
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-08-01 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2105776&HistoricalAwards=false
• 关键词: Collaborative; research; better; understanding; seismic; Collaborative; research; better; understanding; seismic

The subduction zone offshore southwest Mexico is divided into two very different geological regions by the Gulf of Tehuantepec. North of the gulf, the Cocos tectonic plate is shallow as it subducts beneath the North American plate, earthquakes are less frequent, and the ocean trench is close to shore. At Tehuantepec the coastline bends to form the gulf, and south of the gulf the plate is steeper, earthquakes are more frequent, and the trench is far offshore. Located in between, the Gulf of Tehuantepec is considered a seismic gap, in that there have been no recorded large earthquakes associated with the tectonic plates slipping past each other. There are two possible reasons for this. The first is that the rocks of the Tehuantepec Ridge, which is being subducted with the Cocos plate, may be releasing water that lubricates the fault zone, allowing the plates to slowly slide past each other without producing large earthquakes. The second is that the topography of the ridge is mechanically locking the two plates together, in which case a very large earthquake is inevitable when the stress finally builds up to breaking point. In 2017 a large normal earthquake broke across the down-going Cocos plate, a type of earthquake not normally seen in subduction zones, and which could increase the stress and the chances of another large earthquake. This study will make geophysical measurements both onshore and offshore that are sensitive to the presence of water deep in the subduction zone to understand why this earthquake occurred. This work will advance the career of a postdoctoral investigator and strengthen ties between the US and Mexican geophysical communities.In this project an amphibious magnetotelluric (MT) sounding survey coupled with seismotectonic analysis will: (1) Determine differences in coupling/slip regimes in and around the Mexican Tehuantepec seismic gap; (2) Image the Tehuantepec Ridge within the subducted plate to determine its role in the coupling and if it contributes to the break between the Trans-Mexican Volcanic Belt arc system and the Chiapas arc; (3) Image any evidence of fluid infiltration in the Tehuantepec fault. MT soundings have already been successfully used in Mexico to identify changes between stick slip and transient slip within the subduction zone and the geometry of the lower plate. This new study will analyze the unusually large Mw8.2 normal fault Tehuantepec earthquake which is downdip of a slab interface that has no recorded earthquakes. The proposed reasons for why this earthquake occurred are that it was due to slab pull below a strongly coupled interface or that it was due to slab bending along a reactivated, possibly fluid-filled, and poorly coupled, subducted outer rise fault. This work would represent the only physical measurement to directly determine which is correct and determine the link to possible future earthquakes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

西南墨西哥的俯冲带被Tehuantepec的海湾分为两个截然不同的地质区域。 海湾以北，可可构造板是浅层板块，因为它在北美板块下方的俯冲板，地震较少，海沟靠近海岸。 在Tehuantepec，海岸线弯曲以形成海湾，海湾以南板陡峭，地震更频繁，沟渠距离海岸很远。 位于两者之间的Tehuantepec湾被认为是地震差距，因为没有记录的与构造板相互滑过的大地震。 这样做的原因有两个。 首先是，用可可板俯冲的Tehuantepec山脊的岩石可能是释放出润滑断层区的水，使板块可以慢慢滑过彼此，而不会产生大地震。 第二个是山脊的地形在机械上将两个板锁定在一起，在这种情况下，当压力最终升至突破点时，不可避免的地震是不可避免的。 在2017年，大型正常地震横穿了下降的可可板板，这是一种通常在俯冲带中观察到的地震，这可能会增加另一个大地震的压力和机会。 这项研究将使地球物理测量在陆上和海上都对俯冲带深入的水敏感，以了解为什么发生地震。这项工作将推动博士后调查员的职业生涯，并加强美国和墨西哥地球物理社区之间的联系。在这个项目中，这项项目是一项两栖的磁磁纤维（MT）调查，以及Seismotecticonic Analysis的调查，再加上，将：（1）（1）确定墨西哥墨西哥周围和周围墨西哥周围的差异差异。 （2）图像俯冲板中的tehuantepec脊，以确定其在耦合中的作用，以及它是否有助于跨墨西哥火山带弧系统与chiapas弧之间的破裂； （3）图像Tehuantepec断层中流体浸润的任何证据。 MT在墨西哥已经成功使用了MT的声音，以确定俯冲带内的棍子滑动与瞬态滑动之间的变化以及下部板的几何形状。这项新研究将分析异常大的MW8.2正常断层Tehuantepec地震，该断层是没有记录地震的平板界面的倾斜。发生这次地震发生的原因是，它是由于平板在强耦合的界面以下拉动，或者是由于沿着重新激活的，可能充满流体且耦合，俯冲，外层上升断层的平板弯曲所致。这项工作将代表唯一直接确定哪种正确的物理测量，并确定与未来地震的链接。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的知识分子优点和更广泛的影响评估标准通过评估来支持的。