Rapid deployment of onshore/offshore seismic stations in the North Chile Seismic Gap following the April 2014 M8.2 Pisagua earthquake

秘鲁-智利俯冲带经常发生大地震。1877年，智利北部发生了8.8级地震，从那以后，直到2014年4月，该地区再没有发生过大地震。因此，这个长达500公里的区域被称为“北智利地震间隙”。2014年3月下旬，在这个间隙内发生了许多小到中等的地震。活动一般轻微向北迁移。2014年4月2日，前一个震群的北部发生了8.2级地震，随后发生了多次余震，其中包括7.6级地震。余震活动仍在继续，由于该地区的其他地区在一个多世纪以来没有经历过大地震，因此不能排除在不久的将来或中期在该地区发生另一次大地震的可能性。为了测量最近地震间隙破裂区域的余震活动，以及附近可能发生的任何其他事件，我们建议在秘鲁沿海地区和智利近海安装地震仪。这样做有两个主要原因。首先，额外的网络将极大地提高地震间隙区周围台站的覆盖范围，使我们能够生成俯冲带的详细模型。这将对今后分析该地震多发地区的地震活动有很大的帮助。其次，我们对正在进行的地震活动的记录将使我们能够准确地定位余震，并推断发生了什么类型的断层。这将使我们能够非常详细地了解震后过程与之前的大地震事件之间的关系。我们还将使用卫星雷达图像来绘制地球表面由于最近的地震活动而如何移动的地图。这些变形图可以用于计算机模型来估计地表以下断层上发生的滑动的位置和大小——例如，在主震发生的俯冲带界面上。从本质上讲，我们是用表面测量来推断地下过程。我们项目的地震学和卫星组成部分的结果将被综合起来，使我们深入了解北智利地震间隙发生的性质和过程。例如，我们将研究大地震破裂区域与前震/余震序列位置之间的空间关系。另一个重要的问题是确定俯冲带界面上尚未滑动的区域，这些区域可能因此在未来的大地震中破裂。

The Peru-Chile subduction zone hosts many large earthquakes. A M8.8 earthquake occurred in northern Chile in 1877, and since then, no major event had re-ruptured the area prior to April 2014. The 500 km-long zone has therefore become known as the "North Chile seismic gap". In late March 2014, many small to moderate earthquakes occurred within this gap. Activity generally migrated slightly northwards. On 2 April 2014, a M8.2 earthquake occurred in the northern part of the preceding cluster, followed by many aftershocks, including a M7.6 event. Aftershock activity continues and, since the rest of the area has not experienced a major earthquake for well over a century, another large event in the area in the near future or medium term cannot be ruled out. In order to measure aftershock activity in the area of the seismic gap that ruptured recently, in addition to any other events that may occur nearby, we propose to install seismometers in the Peruvian coastal region and also offshore Chile. There are two main reasons for doing this. Firstly, the extra networks will dramatically improve station coverage around the seismic gap area, enabling us to generate detailed models of the subduction zone. This will be of great benefit for future analyses of seismic activity in this earthquake-prone area. Secondly, our records of the ongoing seismic activity will enable us to locate aftershocks accurately and infer what type of faulting occurred. This will enable us to build up a very detailed picture of how post-earthquake processes relate to preceding large seismic events.We will also use satellite radar images to construct maps of how the surface of the Earth has moved as a result of the recent seismic activity. These deformation maps can be used in computer models to estimate the location and magnitude of slip that occurred on faults beneath the surface - for instance, on the subduction zone interface, where the mainshock occurred. Essentially we are using surface measurements to infer sub-surface processes.Results from the seismological and satellite components of our project will be integrated to give us an in-depth understanding of the properties and processes occurring in the North Chile seismic gap. For instance, we will look at the spatial relationship between the area that ruptures in major earthquakes and the location of foreshock/aftershock sequences. Another important issue is to identify areas on the subduction zone interface that have not yet slipped, and that could therefore rupture in major earthquakes in the future.