Collaborative Research: RUI: Investigating Time-Varying Relationships Between Interseismic Coupling, Slow Slip, and Seismicity Along the Mexican Megathrust and Sliver Fault

俯冲带是一个构造板块俯冲到另一个构造板块之下的区域。 在两个板块之间的接触处，大型逆冲断层（巨型逆冲断层）对附近的人口构成重大的地震风险。地震的震级和间隔时间取决于岩石如何沿着断层沿着相互摩擦，以及这种运动如何随时间和空间而变化。一些岩石运动可以通过邻近的构造断层传递到大陆板块内部。因此，为了更好地评估与俯冲带相关的地震危险，需要将板块边界区域作为关键断层系统进行研究。在这里，研究人员分析了与位于墨西哥西海岸的俯冲带相关的地震和地面运动。这个板块边界在过去十年中经历了三次大地震（7.0级）。巨型逆冲断层的关键部分位于陆地之下，深度相对较浅。 这使得断层对人口特别有威胁，但比其他地方更容易研究。为了揭示该地区复杂的地质构造，该团队使用了20多年来收集的高精度GPS和地震记录。研究人员测量断层强度，并确定小地震分布的空间和时间模式。他们还调查缓慢的地面运动，并跟踪俯冲带与陆内断层的相互作用。该项目的成果提高了对俯冲带构造的理解。 它们还改善了墨西哥和其他受巨型逆冲断层威胁的地区的地震危险评估，如阿拉斯加和美国西北部。 该项目促进了新泽西学院和迈阿密大学之间的合作，以及与墨西哥的国际合作。它提供了一个早期的职业女性科学家的支持，一个研究生，并为本科生的培训，特别是从在Science.This研究代表性不足的群体，进一步加深了我们对俯冲巨型逆冲环境的理解。 它利用了墨西哥长达十年的时间序列以及复杂的分析和建模技术，如事件模板匹配和三维有限元建模。它还占了最近的发现，作为观察到的相关的慢滑动事件（SSE）和地震活动发生在地壳银断层，容纳在墨西哥的斜收敛的分割。墨西哥俯冲带呈现出一个浅的板块角，这使得地震和缓慢滑动的震源区靠近陆地和陆地之下。该研究受益于这种几何结构，它允许准确的数据采集。此外，墨西哥的SSE和大逆冲断层地震的复发间隔很短。这使得能够研究弹性回弹的多个周期。该项目有三个主要目标：1）调查墨西哥巨型逆冲断层沿着地震间耦合的时间变化以及与地震活动性的潜在相关性; 2）检查2012年，2014年和2018年SSE和巨型逆冲断层地震之间的时空关系; 3）制定建模策略，以解决巨型逆冲断层和地壳银断层上的SSE和应变积累。每个目标的结果对地震危害和风险评估都有重要的影响，以及是否可以量化这些危害如何随着时间的推移而变化。该奖项反映了NSF的法定使命，并被认为值得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来支持。

Subduction zones are regions where one tectonic plate dives underneath another. At the contact between the two plates, large thrust faults (megathrust faults) pose major seismic risks to nearby populations. The magnitude of earthquakes and the time between them depends on how the rocks grind past one another along the faults, as well as how this movement varies over time and space. Some of the rock movements can be transmitted within the continental plate through adjacent tectonic faults. Therefore, to better assess the earthquake hazards associated with subduction zones, one needs to study the plate boundary region as a system of key faults. Here the researchers analyze the earthquakes and ground movements associated with the subduction zone located on the west coast of Mexico. This plate boundary has experienced three large earthquakes (magnitude 7.0) in the last decade. Key portions of the megathrust fault lie under land and at relatively shallow depths. This makes the fault particularly threatening for the population, yet easier to study than in other locations. To unveil the complex tectonics of the region, the team uses high-precision GPS and seismic recordings collected over two decades. The researchers measure the fault strength and identify patterns in space and time in the distribution of small earthquakes. They also investigate slow ground movements and track the interactions of the subduction zone with intracontinental faults. Outcomes of this project improve the understanding of subduction zone tectonics. They also improve seismic hazard assessment in Mexico and other regions threatened by megathrust faults, as in Alaska and the northwestern US. The project fosters a collaboration between The College of New Jersey and Miami University, as well as international collaboration with Mexico. It provides support for an early career female scientist, a graduate student, and training for undergraduate students notably from groups underrepresented in Science.This research furthers our understanding of subduction megathrust environments. It takes advantage of decadal-long time series in Mexico as well as sophisticated analytical and modeling techniques, such as event template matching and 3D finite-element modeling. It also accounts for recent discoveries, as the observed correlated slow slip episodes (SSEs) and seismicity occurring on a crustal sliver fault that accommodates the partitioning of oblique convergence in Mexico. The Mexico subduction zone presents a shallow slab angle which brings seismogenic and slow-slip source regions close to and beneath land. The study benefits from this geometry which allows for accurate data acquisition. Moreover, SSEs and megathrust earthquakes in Mexico have short recurrence intervals. This enables studying multiple cycles of elastic rebound. The project has three main goals: 1) Investigate temporal variations in interseismic coupling along the Mexican megathrust and potential correlations with seismicity; 2) examine spatial-temporal relationships between SSEs and megathrust earthquakes in 2012, 2014, and 2018; 3) develop a modeling strategy to resolve SSEs and strain accumulation on both the megathrust and a crustal sliver fault. Results from each of these goals have important implications for seismic hazard and risk assessment, and on whether one can quantify how those hazards are changing over time.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.