Publication Date:
2022-09-29
Description:
Megathrust earthquakes impose changes of differential stress and pore pressure in the lithosphere‐asthenosphere system that are transiently relaxed during the postseismic period primarily due to afterslip, viscoelastic and poroelastic processes. Especially during the early postseismic phase, however, the relative contribution of these processes to the observed surface deformation is unclear. To investigate this, we use geodetic data collected in the first 48 days following the 2010 Maule earthquake and a poro‐viscoelastic forward model combined with an afterslip inversion. This model approach fits the geodetic data 14% better than a pure elastic model. Particularly near the region of maximum coseismic slip, the predicted surface poroelastic uplift pattern explains well the observations. If poroelasticity is neglected, the spatial afterslip distribution is locally altered by up to ±40%. Moreover, we find that shallow crustal aftershocks mostly occur in regions of increased postseismic pore‐pressure changes, indicating that both processes might be mechanically coupled.
Description:
Plain Language Summary:
Large earthquakes modify the state of stress and pore pressure in the upper crust and mantle. These changes induce stress relaxation processes and pore pressure diffusion in the postseismic phase. The two main stress relaxation processes are postseismic slip along the rupture plane of the earthquake and viscoelastic deformation in the rock volume. These processes decay with time, but can sustain over several years or decades, respectively. The other process that results in volumetric crustal deformation is poroelasticity due to pore pressure diffusion, which has not been investigated in detail. Using postseismic surface displacement data acquired by radar satellites after the 2010 Maule earthquake, we show that poroelastic deformation may considerably affect the vertical component of the observed geodetic signal during the first months. Poroelastic deformation also has an impact on the estimation of the postseismic slip, which in turn affects the energy stored at the fault plane that is available for the next event. In addition, shallow aftershocks within the continental crust show a good, positive spatial correlation with regions of increased postseismic pore‐pressure changes, suggesting they are linked. These findings are thus important to assess the potential seismic hazard of the segment.
Description:
Key Points:
A poro‐viscoelastic deformation model improves the geodetic data misfit by 14% compared to an elastic model that only accounts for afterslip.
Poroelastic deformation mainly produces surface uplift and landward displacement patterns on the coastal forearc region.
Neglecting poroelastic effects may locally alter the afterslip amplitude by up to ±40% near the region of maximum coseismic slip.
Description:
Helmholtz Association (亥姆霍兹联合会致力)
http://dx.doi.org/10.13039/501100009318
Keywords:
ddc:551
Language:
English
Type:
doc-type:article
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