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

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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.