New 2010 Maule Aftershock Catalog Reveals Structure of the Deep Subduction Interface

Abstract

On 27 February 2010, a Mw 8.8 earthquake occurred near Maule in south‐central Chile. The subsequent rapid deployment of a dense network of seismic stations on land was able to capture the first year of its aftershock sequence. Here, we revisit this data set using picking Artificial Intelligence tools, a 3D velocity model of the region and double‐difference techniques, to obtain a catalog of 146950 well‐constrained events. We observe many features first documented by studies using less dense aftershock catalogs, including the presence of important outer rise seismicity in the north, the occurrence of small earthquake sequences in the volcanic arc, the pervasive faulting associated with the Mw 6.9 11 March 2010 Pichilemu earthquake, and the separation of plate interface seismicity into two groups located at 15–40 km depth and 40–55 km depth. We focus on the deeper part of the plate interface seismicity (40–55 km depth), located at the bottom of the seismogenic zone, to investigate its structure. In this region, earthquakes seem to occur primarily on non‐overlapping planes existing within a ∼1.6 km thick zone. Many of these events form 100 m to km scale long streaks aligned along dip, which might be linked to the presence of afterslip in the region. We speculate that these small lineations may occur within individual blocks smeared along the subduction interface, or alternatively that they may occur within aligned chains of blocks.