Characterising the Northern Chile subduction zone (24⁰S - 31⁰S) with > 165,000 earthquakes

The Atacama segment in Northern Chile (24⁰S to 31⁰S) is a mature seismic gap with no major event (M_w≥8) since 1922. Nonetheless, the region regularly releases stress through shallow and deep slow slip events, and hosts recurring seismic swarm activity. To investigate this seismic gap and its complex seismic-aseismic behaviour, we instrumented the region with almost 200 seismic and geodetic stations between November 2020 and February 2024. Using machine learning techniques, we derived a dense, high-resolution seismicity catalog, encompassing over 165,000 events with double-difference relocated hypocenters. Within the network, we achieve relative location uncertainties below 50 m, enabling the resolution of fine-scale structures. Our catalog details the outer rise, interface, intraplate and upper plate seismicity. Furthermore, we capture anthropogenic sources from mine blasting and offshore active seismic experiments. Here, we focus on three aspects:

• The new slab geometry and it’s influence on the large scale seismic segmentation

• The fine scale space-time segmentation of the subduction interface

• The complex seismic swarms around the 2023 shallow slow slip event in Copiapó, highlighting in detail the underlying mechanisms of slow-to-fast earthquake interaction

Our results provide a holistic view of this complex subduction zone, while at the same time giving insights into fine-scale structures and processes.