Insights into the complexities of a seismogenic subduction zone: Analysis of a high-quality aftershock data set from the 2017 Tehuantepec (M8.2) offshore Mexico earthquake

俯冲带——一个构造板块潜入另一个板块之下的地方——是地球上最具影响力的自然灾害的罪魁祸首。这些包括大地震、海啸和火山爆发，有时是爆炸性的。这些破坏性事件对人类社会构成重大威胁。它们经常造成人员伤亡和经济损失。在过去的一个世纪里，墨西哥俯冲带发生了多次毁灭性的大地震。它的标志是墨西哥海岸外的中美洲海沟。在那里，科科斯板块潜入北美大陆板块之下。它是2017年9月7日墨西哥特万特佩克8.2级地震的罪魁祸首。在这里，研究人员调查了造成这种破坏性事件的原因。他们使用地震后部署的快速地震阵列收集的数据。通过分析高分辨率数据，他们逐渐揭示了俯冲带的过程和地震机制。该项目利用了德克萨斯大学埃尔帕索分校（UTEP）和墨西哥几家机构之间的国际合作伙伴关系。它还为研究生和本科生提供培训，特别是来自科学领域代表性不足的群体的学生。在这里，研究小组分析了2017年特万特佩克地震的高质量、独特的余震数据集。数据是在一次地震部署后收集的，该部署得到了RAPID的支持。快速发展网络扩大了墨西哥国立大学Autónoma（墨西哥国立大学）部署的永久和临时网络。它包括2017年10月初部署的10个宽带仪器（记录了6个月的数据）和51个utep拥有的节点（5赫兹，3分量地震检波器，活动22天）。在宽带部署期间，Sismológico国家服务中心（SSN）记录了3万多次余震。这突出了地震产生的坚固性。该项目的目标是回答与俯冲带过程有关的基本和具体问题。由社区努力决定的基本问题包括：大地震发生的时间和地点？俯冲输入的空间变化如何影响地震活动性和岩浆活动？地表过程是如何与俯冲联系起来的？关于墨西哥俯冲带的具体问题是：特万特佩克地震是否会对上板块产生载荷，并可能引发板块界面上的大地震？特万特佩克地震和随后的地震有联系吗？这三次地震分别是2017年9月19日墨西哥莫雷洛斯州-普埃布拉地震（里氏7.1级）、2018年2月18日墨西哥皮诺特帕国家地震（里氏7.2级）和2020年6月23日克鲁塞西塔地震（里氏7.4级）。为了回答这些问题，研究人员合并了各种数据集，为五种互补方法奠定了基础：1)计算高分辨率余震数据集；2)分析地震活动性和应力，3)寻找地震触发机制，4)确定俯冲带的结构，5)整合结果以解决遗留问题。该项目加强了UTEP与墨西哥国立大学、SSN和Autónoma de Ciudad Juárez大学之间的强有力合作。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Subduction zones – where one tectonic plate dives beneath another – are responsible for the most impactful natural hazards on the planet. Those include large earthquakes, tsunamis, and volcanic eruptions which at times are explosive. These destructive events present major threats to human societies. They often cause human casualties and economic losses. The Mexican subduction zone has been responsible for large, devasting earthquakes throughout the past century. It is marked by the Middle American Trench off the coast of Mexico. There, the Cocos Plate dives beneath the continental North American Plate. It was responsible for the September 7, 2017 Tehuantepec, Mexico earthquake of magnitude 8.2 on the Richter scale. Here, the researchers investigate what caused this destructive event. They use data collected by a rapid seismic-array deployment following the earthquake. Analyzing the high-resolution data, they gradually unveil subduction-zone processes and earthquake mechanisms. This project leverages an international partnership between the University of Texas at El Paso (UTEP) and several institutions in Mexico. It also provides training for graduate and undergraduate students, notably from groups underrepresented in science.Here the team analyze a high-quality, unique aftershock dataset from the 2017 Tehuantepec earthquake. The data were collected after a seismic deployment supported by a RAPID award. The RAPID network augmented permanent and temporary networks deployed by the Universidad Nacional Autónoma de Mexico (UNAM). It included ten broadband instruments deployed in early Oct. 2017 (that recorded data for 6 months) and 51 UTEP-owned Nodes (5-Hz, 3-component geophones, active for 22 days). During the broadband deployment, the Servicio Sismológico Nacional (SSN) recorded over 30,000 aftershocks. This highlights the robust nature of earthquake generation. The project goal is to answer fundamental and specific questions that relate to subduction zone processes. Fundamental questions, determined by community efforts, include: when and where do large earthquakes happen? How do spatial variations in subduction inputs affect seismicity and magmatism? How are surface processes linked to subduction? Specific questions about the Mexican subduction zone are: will the Tehuantepec earthquake load the upper plate and possibly trigger a large earthquake on the plate interface? Are the Tehuantepec and subsequent earthquakes linked? These earthquakes are the September 19, 2017 Morelos-Puebla, Mexico (M7.1), the February 18, 2018 Pinotepa Nacional, Mexico (M7.2), and the June 23, 2020 (M7.4) La Crucecita. To answer these questions, the researchers merge the various datasets which builds a foundation for five complementary approaches: 1) calculate a high-resolution aftershock dataset; 2) analyze seismicity and stress, 3) search for earthquake triggering mechanisms, 4) define the structure of the subduction zone, and 5) integrate results to address remaining questions. This project strengthens a strong collaboration between UTEP and, in Mexico, UNAM, the SSN, and the Universidad Autónoma de Ciudad Juárez.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.