RAPID: GPS Observations of Co- and Post-seismic Deformation in the Argentine Andes, Precordillera, and Sierras Pampeanas from the 16 Sep 2015, Mw 8.3, Illapel, Chile, Earthquake

来自孟菲斯大学的科学家与来自Nivología、Glaciología y Ciencias Ambientales研究所的科学家合作，将在阿根廷圣胡安安装4个新的连续GPS台站，并对35个基准点进行震后GPS测量。这些测量结果将用于确定2015年9月16日智利Illapel近海Mw8.3大逆冲断层地震的中场同震和震后变形。这些测量记录了地震以东100-400公里处的形变场，将补充智利地震网在智利震中附近地区的类似活动。中场到远场信号很小，但很重要，因为与大得多的近场信号相比，它们的建模和理解都很差。中远场信号采样了南美洲板块岩石圈应力导层、西部安第斯山脉下的粘弹性地幔楔和东部的南美洲板块上地幔的响应。南美洲-纳斯卡板块边界是独特的，因为它是唯一一个主要的会聚边界，在那里，从近场到远场，可以在俯冲系统的上板块一侧观察到。沿着南美洲-纳斯卡板块边界沿着发生的大规模逆冲断层地震产生了横跨整个大陆的大而快速的同震变形。它们还产生了板块范围的震后变形，这些变形最初比震间变形更快，甚至可以超过同震偏移。这些快速变化的变形可能通过在时间上集中地震形变或触发地震而在构造中起重要作用。这些信号随时间衰减，因此需要快速部署GPS，以便在信号降低到检测水平以下之前捕获变形信号。拟议的活动通过提供有助于确定可用于减灾工作的余震区域的数据，推动取得预期的社会成果，并有助于了解该区域的地震危险。该项目还通过扩大全球定位系统网络和调整国家大地测量参考框架，帮助加强研究基础设施。

Scientists from the University of Memphis in collaboration with scientists from the Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales will install 4 new continuous GPS stations and perform post-earthquake survey GPS measurements on 35 benchmarks in San Juan, Argentina. The measurements will be used to determine the mid-field co- seismic and post-seismic deformations of the September 16, 2015 Mw 8.3, megathrust earthquake offshore Illapel, Chile. These measurements, which capture the deformation field 100-400 km to the east of the earthquake, will complement similar activities in the immediate epicentral area in Chile from the Chilean Seismic Network. The mid-field to far-field signals are small, but significant as they are both poorly modeled and poorly understood in comparison to the much larger near-field signals. The mid- to far-field signals sample the response of the South America plate lithospheric stress guide, and the viscoelastic mantle wedge under the Andes in the west, and South America cratonic upper mantle to the east.The South America-Nazca plate boundary is unique as it is the only major convergent boundary where an almost complete aerial sampling of megathrust earthquake cycle deformation, from near- to far-field, can be observed in the upper plate side of a subduction system. Megathrust earthquakes along the South America-Nazca plate boundary produce large, rapid co-seismic deformations stretching across the whole continent. They also produce plate-wide post-seismic deformations that are initially faster than the inter-seismic deformations and can even surpass the co-seismic offset. These rapidly changing deformations may play an important role in tectonics by temporally concentrating aseismic deformation or triggering earthquakes. These signals decay with time, thus a rapid GPS deployment is necessary to capture the deformation signal before the signals decrease below the detection level. The proposed activity advances desired societal outcomes by providing data that would aid in determining regions of aftershocks that could be used in hazard mitigation efforts and would contribute to the understanding of earthquake hazard in the region. The project also contributes to enhanced infrastructure for research through the expansion of a GPS network and to adjustment of national geodetic reference frames.