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Integrated geophysical characteristics of the 2015 Illapel, Chile, earthquake

Journal of Geophysical Research B: Solid Earth

By:
, ORCID iD , ORCID iD , , ORCID iD , , and ORCID iD
https://doi.org/10.1002/2016JB013617

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Abstract

On 16 September 2015, a Mw 8.3 earthquake ruptured the subduction zone offshore of Illapel, Chile, generating an aftershock sequence with 14 Mw 6.0–7.0 events. A double source W phase moment tensor inversion consists of a Mw 7.2 subevent and the main Mw 8.2 phase. We determine two slip models for the mainshock, one using teleseismic broadband waveforms and the other using static GPS and InSAR surface displacements, which indicate high slip north of the epicenter and west-northwest of the epicenter near the oceanic trench. These models and slip distributions published in other studies suggest spatial slip uncertainties of ~25 km and have peak slip values that vary by a factor of 2. We relocate aftershock hypocenters using a Bayesian multiple-event relocation algorithm, revealing a cluster of aftershocks under the Chilean coast associated with deep (20–45 km depth) mainshock slip. Less vigorous aftershock activity also occurred near the trench and along strike of the main aftershock region. Most aftershocks are thrust-faulting events, except for normal-faulting events near the trench. Coulomb failure stress change amplitudes and signs are uncertain for aftershocks collocated with deeper mainshock slip; other aftershocks are more clearly associated with loading from the mainshock. These observations reveal a frictionally heterogeneous interface that ruptured in patches at seismogenic depths (associated with many aftershocks) and with homogeneous slip (and few aftershocks) up to the trench. This event likely triggered seismicity separate from the main slip region, including along-strike events on the megathrust and intraplate extensional events.

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Additional publication details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Integrated geophysical characteristics of the 2015 Illapel, Chile, earthquake
Series title:
Journal of Geophysical Research B: Solid Earth
DOI:
10.1002/2016JB013617
Volume:
122
Issue:
6
Year Published:
2017
Language:
English
Publisher:
American Geophysical Union
Contributing office(s):
Geologic Hazards Science Center
Description:
21
First page:
4691
Last page:
4711
Country:
Chile
City:
Illapel