RAPID: Seismic Deployment for Capturing Aftershocks of the September 2017 Chiapas (M=8.1) and Puebla (M=7.1) Mexico Earthquakes

9月7日的墨西哥恰帕斯（M=8.1）地震和9月19日的墨西哥普埃布拉（M=7.1）地震发生在一个俯冲带，在那里海洋科科斯板块沿着美洲中部海沟俯冲到北美大陆板块之下。两次地震都造成了重大的破坏和生命损失。美国地质调查局（USGS）的初步结果表明，这些中深度（50-60公里深度）地震并没有沿着板块界面发生，而是使俯冲的大洋板块发生了伸展断裂破裂。这些不是典型的沿中美洲海沟俯冲界面的俯冲板块边界挤压事件。此外，这两次地震相距约640公里，这一距离足以表明它们之间没有联系。我们将研究关于这些地震的几个遗留问题，包括：这些地震是否会对上部板块产生载荷，并可能在板块界面上引发同等或更大的地震？这些是板材弯曲的结果吗？余震是否向隐没带的锁定带迁移？这些中深度地震是破裂进入地幔的吗？为什么中深度地震造成如此大的破坏？这些地震是由动应力引起的吗？我们将在这两次地震周围和地震之间部署地震传感器，并与墨西哥的同事协调分析收集到的数据，以此来解决这些问题。我们建议立即在9月7日墨西哥恰帕斯州（M=8.1）和9月19日墨西哥普埃布拉州（M=7.1）地震的震中附近部署10个宽带和50个uep拥有的节点（5赫兹，3分量检波器）地震仪，以记录其余震并绘制重灾区附近的浅层地球结构图。美国地质调查局（USGS）的初步结果表明，这两次最大的地震都是不寻常的：地震都没有发生在板块界面上，都发生在中等深度（50-60公里深），而且两次地震都发生在具有伸展断裂作用的俯冲大洋板块内，而不是典型的沿中美洲海沟的俯冲板块边界挤压事件。此外，两次地震之间的距离约为640公里，比两个断层长度还长，在这个距离上，静态触发力往往非常小，表明它们之间没有联系。10个宽带仪器将部署6个月，而节点将部署30天，因为这是它们电池寿命的剩余时间。然而，这些节点允许在目标区域快速部署许多站点，特别是在现场特征广泛损坏的区域，这是此类部署对这些仪器的第一次测试。我们希望解决有关上述地震的一些关键问题。对收集到的数据进行分析，将允许从余震位置识别断层，从确定断层解决方案中确定地震引起的应力释放和方向，以及在广泛破坏区域绘制现场特征和现场影响。此外，这些数据还可以用来对该区域进行成像，以更好地确定活动板块的边界。

The September 7 Chiapas, Mexico (M=8.1) and the September 19 Puebla, Mexico (M=7.1) earthquakes occurred along a subduction zone, where the oceanic Cocos Plate subducts beneath the continental North American Plate along the Middle American Trench. Both earthquakes caused significant damage and loss of life. Initial United States Geological Survey (USGS) results show that these intermediate depth (50-60 km depth) earthquakes did not occurred along the plates interface, but ruptured the subducting oceanic plate with extensional faulting. These were not the typical subduction plate boundary compressional events along the subduction interface of the Middle American Trench.  Furthermore, the earthquakes were located about 640-km from each other, a far enough distance to suggest no link between them.  We will investigate several questions remaining about these earthquakes including: Will these earthquakes load the upper plate and possibly trigger an equal or larger earthquake on the plate interface? Are these the result of plate bending?  Do the aftershocks migrate to the locked zone in the subduction zone?  Did these intermediate depth earthquakes rupture into the mantle? Why did the intermediate depth earthquakes create so much damage? Are these earthquakes linked due to dynamic stresses? We will address these questions by deploying seismic sensors around these two earthquakes and in between them and analyzing the data collected in coordination with our colleagues in Mexico.We propose to immediately deploy 10 broadband and 50 UTEP-owned nodes (5-Hz, 3-component geophones) seismometers near the epicenters of the September 7 Chiapas, Mexico (M=8.1) and the September 19 Puebla, Mexico (M=7.1) earthquakes to record their aftershocks and to map shallow earth structure near heavily damaged regions. Initial United States Geological Survey (USGS) results show that the two largest earthquakes were unusual: neither earthquake occurred along the plate interface, both were at intermediate depth (50-60 km depth), and both earthquakes ruptured within the subducting oceanic plate with extensional faulting, not the typical subduction plate boundary compressional events along the Middle American Trench.  Furthermore, the earthquakes were ~640-km apart, longer than two fault lengths, a distance at which static triggering forces tend to be very small, suggesting no link between them. The 10 broadband instruments will be deployed for 6 months, while the nodes will be deployed 30 days, since this is the extant of their battery life. The nodes, however, allow for numerous stations to be deployed rapidly in targeted regions, especially regions of extensive damage for site characterization, and this is the first test of these instruments for this type of deployment. We wish to address some key questions on the earthquakes, defined above. Analysis of the data collected will allow for fault plane identification from aftershock locations, stress release and orientation caused by the earthquakes from the determination of fault plane solutions, and for site characterization and site effects to be mapped in regions of extensive damage. Furthermore, the data can be used to image the region to better define the active plate boundaries.