Coseismic and post-seismic gravity disturbance induced by seismic sources using a 2.5-D spectral element method
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Abstract
I present a prescription for computing free-air coseismic and post-seismic gravity changes induced by seismic sources in a viscoelastic earth model. I assume a spherical earth geometry and a 2.5-D calculation, that is, 3-D motions that satisfy the equations of quasi-static equilibrium on a 2-D viscoelastic structure. The prescription permits application to regional gravity computations where a 2-D structure adequately represents the structural heterogeneity. I use a hybrid approach where deformation is computed on a discretized domain and the resulting density perturbations are expanded with spherical harmonics to produce the free-air gravity field. Starting with a solution to the equations of quasi-static displacements in the Laplace transform domain for a given dislocation source, I solve Poisson’s equation using Lagrangian interpolation on spectral element nodes to compute the required deformation quantities that contribute to free-air gravity. A numerical inverse Laplace transform then yields time domain results. This methodology is tested with analytic solutions on a spherically stratified viscoelastic structure, then applied to evaluate the effect of a descending slab of relatively high viscosity on post-seismic gravity in a megathrust faulting setting.
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Coseismic and post-seismic gravity disturbance induced by seismic sources using a 2.5-D spectral element method |
| Series title | Geophysical Journal International |
| DOI | 10.1093/gji/ggaa151 |
| Volume | 122 |
| Issue | 2 |
| Year Published | 2020 |
| Language | English |
| Publisher | Royal Astronomical Society |
| Contributing office(s) | Earthquake Science Center |
| Description | 18 p. |
| First page | 827 |
| Last page | 844 |
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