Seismicity distribution in the vicinity of the Chile Triple Junction, Aysén Region, southern Chile

The Aysen Region, southern Chile, is the area located at the southern end of the Nazca-South America subduction zone, to the east of the Chile Triple Junction. This region has historically presented low levels of seismicity mostly related to volcanism. Nonetheless, a seismic sequence occurred in 2007, related to the reactivation of the strike-slip Liquine-Ofqui Fault System (LOFS), confirmed that this region is not exempt from major seismic activity M ∼ 7. Here we present results from background local seismicity of two years (2004–2005) preceding the sequence of 2007. Event magnitudes range between 0.5 and 3.4 ML and hypocenters occur at shallow depths, mostly within the upper 10 km of crust, in the overriding South American plate. No events were detected in the area locus of the 2007 sequence, and the Wadati–Benioff (WB) plane is not observable given the lack of subduction inter-plate seismicity in the area. A third of the seismicity is related to Hudson volcano activity, and sparse crustal events can be spatially associated with the trace of the Liquine-Ofqui fault, showing the largest detected magnitudes, in particular at the place where the two main branches of the LOFS meet. Other minor sources of seismicity correspond to glacial calving in the terminal zones of glaciers and mining explosions.