Geodynamical simulation of the effects of ridge subduction on the scale of the seismogenic zone south of Chile Triple Junction

Earthquakes are much more frequent to the north of Chile Triple Junction than to the south, where the thermal anomaly is also more significant. To study the effects of ridge subduction on the thermally defined seismogenic zone, two-dimensional finite element models were established based on the geology of Chile Triple Junction, the process of ridge subduction was simulated, and the effects of the initial slab dip and the convergence rate on the seismogenic zone were compared. The results show that the width of the seismogenic zone decreases during the ridge subduction, inducing earthquakes to occur much less to the south than to the north of Chile Triple Junction. By comparing the observed data in the vicinity of the profiles with the numerical simulation results, we find that the numerical simulation can roughly reflect the width of the interplate seismogenic zone and the surface heat flow in the area of Chile Triple Junction. At the same convergence distance, a larger convergence rate comes with a wider seismogenic zone and the deeper the downdip limit of the seismogenic zone, the higher the surface heat flow in the vicinity of the trench. Compared with the convergence rate, factors such as slab dip have little effect on the surface heat flow. In the process of ridge subduction, larger the slab dips leads to narrower seismogenic zones. When the effect of shear heating is included in the simulation, the width of the seismogenic zone in the process of ridge subduction can shrink to about 15 km and the depth of the seismogenic zone is small. Such a narrow and shallow seismogenic zone makes it hard for earthquakes to occur and for the Wadati-Benioff plane to be observed in some areas south of Chile Triple Junction.