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

Lead Research Organisation: University of Liverpool
Department Name: Earth, Ocean and Ecological Sciences


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.

Planned Impact

We have identified the following as parties likely to benefit from our research project:

1. Seismologists working on the Peru-Chile subduction zone
Since our data will be made available online through IRIS (Incorporated Research Institutions for Seismology), any seismologists interested in investigating this area will be able to make use of them.

3. Government, geological institutes and decision-makers in Peru/Chile
Official institutions and individuals who make important decisions concerning local/regional hazards and public safety will benefit from our work, since it aims to give a much clearer understanding of seismic/aseismic activity in the seismic gap. One objective is to be able to identify areas on the subduction zone plate interface that have yet to rupture, and which of those, if they did rupture, could be likely to cause tsunamis. Thus, if (when) another major event does occur, informed decisions will be able to be made.

3. NERC DTP students
We anticipate designing one or two NERC DTP studentships around the seismological and SAR data accumulated during the project. The students would likely carry out (a) travel time/waveform tomography to produce a detailed 3D velocity model of the area, and (b) analysis of postseismic InSAR data to identify which areas of the plate interface have slipped, and by how much, and therefore areas of potential future rupture.

4. Undergraduate and postgraduate students at the University of Liverpool
Students at the university will benefit from this project by (a) seeing their lecturers/supervisors go into the field to make deployments for research purposes, and (b) learning about the motivation for, and results of, the project as it develops.

5. School pupils and teachers
We are involved in a number of schools liaison projects involving earthquakes, for instance the BGS School Seismology Project, and a now-annual Earthquakes in Action workshop we run at Liverpool. We are currently organizing our second workshop for early July, and so we would integrate the proposed research into the material. During our deployment trip, we will make a video of how scientists work in the field and the challenges involved, and show this to the workshop attendees to highlight how seismologists operate and demonstrate that practical work is a big part of research. The video would also be made available on our department website for general viewing.

6. General public interested in this project
In our last urgency proposal we kept a fieldwork blog on all of our three field trips to Chile, which was very popular and had lots of readers, with many posting comments. We plan to do this again for the current project. In addition, we will make use of Twitter and our Earth Sciences at Liverpool Facebook page to post updates on the project.

7. The general academic community and other interested readers
As we did for our previous urgency grant, we anticipate ultimately producing several publications from this research project, although most of these would be published after the end of the one-year grant period.


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