Numerical wave propagation study of the unusual response of Nevados de Chillan volcano to two aftershocks of the 2010 M-W=8.8 Maule earthquake

Farias, Cristian - Galvan, Boris
Datos de publicación:
In 2012, two large aftershocks of the M-W = 8.8 Maule, Chile earthquake occurred near the Central Chilean coast. Both events, with magnitudes M-W = 6.1 and M-W = 7.1 were located about 200 km away from the volcanic/hydrothermal Nevados de ChillAn (NdC) complex. The system responded with a significant increase in seismicity to the M-W = 6.1 event, and with a reduction in seismicity following the latter, larger M-W = 7.1 earthquake. To understand the physical changes induced by both earthquakes at the NdC, we set up a numerical wave propagation study. Our results show that these observations likely result from dynamic changes at the NdC complex during the passage of the seismic waves. In the case of the M-W = 6.1 aftershock, the extensive stress transfer was large enough to induce changes at the hydrothermal system, which could have later led to an increase in fluid-driven seismicity. In the case of the M-W = 7.1 earthquake, the oblique arrival of seismic waves to the main fault of the NdC due to the M-W = 7.1 earthquake induced slight compressions at the reservoir and created openings in the main fault, promoting fluid migration, which can explain the reduction in seismicity beneath the main craters of the volcano. Results also show that the geometry of an underlying fault system can influence the volumetric response, suggesting that the role of local structures in earthquake-volcano interactions influence the behavior of triggered systems and should therefore not be disregarded. (C) 2019 Elsevier B.V. All rights reserved.

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