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Northern Chile intermediate-depth earthquakes controlled by plate hydration

Abstract : We investigate the variations of the seismic source properties and aftershock activity using kinematic inversions and template-matching, for six large magnitude intermediate-depth earthquakes occurred in northern Chile. Results show similar rupture geometry and stress drop values between 7-30 MPa. Conversely, aftershocks productivity systematically decreases for the deeper events within the slab. Particularly there is a dramatic decrease in aftershock activity below the 400-450 ºC isotherm-depth, which separates high and low-hydrated zones. The events exhibit tensional focal mechanisms at unexpected depths within the slab, suggesting a deepening of the neutral plane, where the extensional regimen reaches the 700-800ºC isotherm-depth. We interpret the reduction of aftershocks in the lower part of the extensional regime as the absence of a hydrated-slab at those depths. Our finding highlights the role of the thermal-structure and fluids in the subducting plate, in controlling the intermediated-depth seismic activity and shed new light in their causative mechanism.
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https://hal.univ-grenoble-alpes.fr/hal-03197367
Contributor : Leoncio Cabrera <>
Submitted on : Tuesday, April 13, 2021 - 5:43:07 PM
Last modification on : Thursday, April 15, 2021 - 3:18:27 AM

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Leoncio Cabrera, Sergio Ruiz, Piero Poli, Eduardo Contreras-Reyes, Axel Osses, et al.. Northern Chile intermediate-depth earthquakes controlled by plate hydration. Geophysical Journal International, Oxford University Press (OUP), 2021, 226 (1), pp.78-90. ⟨10.1093/gji/ggaa565⟩. ⟨hal-03197367⟩

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