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--一个板块俯冲到另一个板块之下--是地球上影响最大的自然灾害的罪魁祸首。这些包括大地震、海啸和火山喷发，这些喷发有时是爆炸性的。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，墨西哥俯冲带一直是大地震的罪魁祸首。它以墨西哥海岸外的中美洲海沟为标志。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，研究人员调查了是什么导致了这一破坏性事件。他们使用地震后快速部署地震台阵收集的数据。通过对高分辨率数据的分析，他们逐渐揭示了俯冲带过程和地震机制。该项目利用了德克萨斯大学埃尔帕索分校(UTEP)和墨西哥几个机构之间的国际伙伴关系。它还为研究生和本科生提供培训，特别是来自科学界代表性不足的群体。在这里，该团队分析了2017年Tehuantepec地震的高质量、独特的余震数据集。这些数据是在一次地震部署后收集的，该部署得到了一项快速奖励的支持。该快速网络扩大了墨西哥国立自治大学(UNAM)部署的永久和临时网络。它包括2017年10月初部署的10台宽带仪器(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，国家地震服务中心(SSN)记录了30,000多次余震。这突显了地震产生的强健性质。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和岩浆活动？地表过程如何与俯冲联系在一起？关于墨西哥俯冲带的具体问题是：特万特佩克地震是否会加载上板块，并可能在板块界面上引发大地震？特万特佩克地震和随后的地震有联系吗？这些地震分别是2017年9月19日墨西哥莫雷洛斯-普埃布拉7.1级地震，2018年2月18日墨西哥皮诺特帕国家地震7.2级，以及2020年6月23日La Crucecita地震7.4级。为了回答这些问题，研究人员合并了各种数据集，这为五种互补的方法奠定了基础：1)计算高分辨率余震数据集；2)分析地震活动和应力；3)搜索地震触发机制；4)确定俯冲带的结构；5)综合结果以解决剩余问题。该项目加强了UTEP与墨西哥UNAM、SSN和华雷斯公民大学之间的紧密合作。该奖项反映了NSF的法定使命，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，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.