Interseismic COUPLING in Peru / Chile

Summary

Among the strongest earthquakes in the world are those related to the South American subduction zone. This project focuses on the seismic gap in the Arica bend, which extends from northern Chile to southern Peru, the extent of which corresponded to the historical earthquakes in mega-thrust in 1868 and 1877 to the devastating tsunamis. Since then, the Arequipa earthquake (2001) has reduced the extent of the gap to the north, but 600km of the gap has remained unbroken since the end of the 19th century. This is an area identified as a mature seismic gap. One of the questions is whether this seismic gap zone actually accumulates intersismic deformation. The objective of this project is to finely map the inter-seismic coupling in this area to assess the potential for a future large subduction earthquake. This will make it possible to assess the extent of blocked areas that are expected to break during a future major earthquake and to locate areas where coupling is weaker, and which could act as a barrier to the propagation of seismic failure. This will make it possible to better characterize seismic hazard and loading mechanisms on the seismogenic zone.

For the moment, efforts have focused mainly on the Chilean part of the gap. Also, to complete the measurements in the north, in June 2012 we carried out a densification of the GPS campaign network in southern Peru in a 100km lane along the coast, because it is a region where having a high data density is critical to constrain interseismic coupling models on the subduction interface. In this project, we are requesting funding for a second measurement campaign for the 33 GPS points installed and measured in 2012, which will allow us to obtain a first estimate of the inter-seismic movement in southern Peru.

Figure 1 : Left : Resolution of coupling models prior to this project (Chlieh et al. 2012). Right : Map of the GPS campaign points existing in Arica’s elbow. The network represented by blue circles was installed in southern Peru in June 2012 as part of this project. Old ruptures are indicated in white (historical ruptures) and red (instrumental earthquakes).