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Spatiotemporal Evolution of Postseismic Stress and Aftershocks Following the 2010 Mw 8.8 Maule Earthquake

Description: 

Following major earthquakes in subduction zones, transient deformation and aftershocks occur. The spatiotemporal behavior of seismicity and its controlling physical mechanisms continue to be debated among geoscientists. Here, we focus on the space-time distribution of postseismic stress changes and aftershocks in subduction zones with a case study of the 2010 Mw8.8 Maule earthquake in Chile. Previous studies have identified pore pressure diffusion as a possible mechanism of the aftershocks that followed the 2014 Mw8.1 Iquique earthquake and linked the spatial migration of aftershocks around the rupture region of the 2015 Illapel earthquake to poroelasticity. Motivated by these examples, we design three-dimensional finite-element models to explore the seismic and aseismic megathrust behavior during the Maule earthquake sequence. We first compare results from our 3D models with the coseismic displacements of the Maule event. We then use time-dependent 3D models to simulate postseismic afterslip, poroelastic rebound, and viscoelastic relaxation and characterize the spatiotemporal patterns of the deformation and Coulomb stress change. Poroelasticity produces positive and negative Coulomb stresses above and below the fault plane, respectively, with its temporal decay faster than viscoelastic Coulomb stresses. The viscoelastic scenario produces mainly positive Coulomb stresses that are concentrated within and below the slab, with stress amplitudes depending on the viscoelastic rheology and crustal thickness. However, the viscoelastic stresses are at least two orders of magnitude smaller than poroelastic stresses, indicating its potential impact mainly on long-term triggering of seismicity. We next compare the characteristics of postseismic deformation and stress changes in our models with the aftershocks from Maule to understand the mechanisms that control seismicity evolution in space and time.

Session: From Geodynamics to Earthquake Rupture, Models That Cross Time- and Length-Scales [Poster Session]

Type: Poster

Date: 5/3/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Segun

Student Presenter: Yes

Invited Presentation: 

Authors