Seismic cycle segmentation in Central Chile subduction zone due to fault geometry anomalies

From the extremely short termed seismic catalogs on the Chilean subduction zone, there are great earthquakes that seem to have ruptures arrested at significant geometric anomalies of the subduction interface, such as sudden strike direction changes or subduction of sea mountain chains. We use a quasi-dynamic boundary element method with a Galerkin approximation to model slip-rate on each point on the fault to investigate the spatial heterogeneous nucleation and slip-rates at the Central Chile subduction zone segment. For these simulations, we assume constant spatial distribution of rate and state frictional properties. The seismic cycle simulations are calculated on a non-planar subduction interface geometry, with an oblique convergence-rate of 66 mm/yr. Our simulations span over 5000 years, where we obtain rupture areas, moment magnitudes and static stress drops for approximately 20 earthquakes. The scaling between rupture area and moment magnitude is quite similar to values reported in the literature. And the static stress drops are consistent with past observations of global and regional average stress drops worldwide. In addition, our results show that the flat slab zone, (roughly between 20º and 33º) acts as a barrier, stopping eighteen earthquakes with magnitudes between Mw 8.5-9.3, which rupture south and north of the barrier. Our simulations show only two larger earthquakes that are able to pass through this barrier, and we do not observe earthquake nucleation within the barrier zone. Our results indicate that geometry and oblique convergence are the main causes of the observed segmentation along strike of the subduction zone, as well as observed maximum magnitude for events that are not able to pass through the barrier zone.