Seismotectonic Consequences of the Strong Earthquake Mauli (February 27, 2010, <i>M</i><sub>w</sub> = 8.8) in Chile: Digital Modeling of the Crust Stress-State of the Western Margin of the South American Plate

Abstract

This article presents seismotectonic consequences of the strong Mauli earthquake in Chile, which occurred on the February 27, 2010, Mw = 8.8. The consequences are considered as a manifestation of a large-scale fragment of the general seismotectonic process on the western edge of the South American plate (Chilean sector). Our study shows that manifestations of postseismic processes of the Maule earthquake cover a much larger area compared to the epicentral zone of the aftershocks. Based on the comparison of the results of numerical modeling of the stress-strain state before and after the earthquake, seismological, geodetic, and satellite data, an alternative model of the development of the seismotectonic process in the Chilean sector of the South American plate was proposed. The stress-strain modeling was performed by the finite element method. The source of the Mauli earthquake, at a depth of 33 km, falls into the region of relatively high values of compression stresses and positive maximum shear stresses. It was shown, that other strong earthquakes of the Chilean sector in the interval of depths from 20 to 50 km are caused by high concentration of tectonic stresses in the region of transition from oceanic to continental lithosphere. Within the framework of the proposed model of the seismotectonic process, ruptures weaken the contact between the oceanic and continental lithosphere after strong earthquakes. Abrupt sinking of the continental lithosphere into the mantle causes an increase in viscous melt pressure, promotes penetration into mega-cracks, and rises to the surface, causing subsequent volcanic eruptions. It is shown that the results obtained in comparison with the coseismic consequences of earthquakes do not contradict these results of numerical modeling and give new insights into the structure of the lithosphere in the continent‒ocean transition zone and the development of the seismotectonic process.