Earthquake segmentation in northern Chile correlates with curved plate geometry

Abstract

We performed an integrated analysis of the coseismic slip, afterslip and aftershock activity of the 2014 M w 8.1 Pisagua earthquake. This earthquake seems to be spatially located between two major historical earthquakes, the 1868 M w 8.8 earthquake in southern Peru and the 1877 M w 8.5 earthquake in northern Chile. Continuous GPS data were used to model the coseismic slip of the mainshock and the largest aftershock (M w 7.6). The afterslip was modeled for 273 days (end of year 2014) after the largest aftershock, revealing two patches of afterslip: a southern patch between the mainshock and the largest aftershock and a patch to the north of the mainshock. Observations from the seismic network indicate that aftershocks were concentrated near the southern patch. Conversely, the northern patch contained hardly any aftershocks, indicating a dominant aseismic slip. The Pisagua earthquake occurred within a prominent, curved section of the Andean subduction zone. This section may have acted as a barrier for the largest historical earthquakes and as an isolated segment during the Pisagua earthquake.