Verification test for classical volcano-seismological problems by spectral element method (SEM)
Résumé
The accurate simulation of seismic wave propagation in a realistic 3-D volcano model is essential to understand the complicated physical processes of magma and gas behaviors at depth. We adopt a spectral element method (SEM), a code EFISPEC3D (De Martin, BSSA, 2011), which shows a good accuracy and numerical stability in the simulations of regional ground motions. For verifying the performance, we consider two classical problems in volcano-seismology, brought by Ohminato & Chouet (BSSA, 1996) and Mogi (BERI,1956). In the first case, a shallow explosive source is embedded in a 3D homogeneous medium with a gaussian-hill like topography. The good agreement is obtained with the results from Ohminato & Chouets (1996). Slight differences in phase and amplitude appear in the late part of the signals and these are due to the different implementation of boundary conditions. Secondly, static deformation of the flat ground surface due to an explosive source is compared with the analytical solution of Mogi (1956). The original formulation of Mogi (1956) is given by a pressure change of a sphere, but we introduce an equivalent seismic moment in the SEM simulation. In order to obtain the static deformation field, we ran the simulation during long time so that all the seismic waves go away. The good fit is obtained, except for the far field due to the absorbing boundary condition of the SEM.