On the validity of the planar wave approximation to compute synthetic seismograms of teleseismic body waves in a 3-D regional model

Vadim Monteiller (1) , Stephen Beller (2) , Bastien Plazolles (2) , Sébastien Chevrot (2)

1 LMA - Laboratoire de Mécanique et d'Acoustique [Marseille]
2 GET - Géosciences Environnement Toulouse

Injection methods are a very efficient means to compute synthetic seismograms of short period teleseismic body waves in 3D regional models. The principle is to inject an incident teleseis- mic wavefield inside a regional 3D cartesian spectral-element grid. We have developed an open source package which allows us to inject either an incident plane wave, computed with a frequency-wavenumber method, or the complete wavefield computed in a spherically sym- metric reference Earth model with AxiSEM. The computations inside the regional spectral- element grid are performed with SPECFEM3D Cartesian. We compare the efficiency and re- liability of the two injection methods for teleseismic P waves, considering a wide range of epicentral distance and hypocentral depths. Our simulations demonstrate that in practice the effects of wavefront and Earth curvature are negligible for moderate size regional domains (several hundreds of kilometers) and for periods larger than 2 s. The main differences ob- served in synthetic seismograms are related to secondary phases that have a different slowness from the one of the reference P phase.

Domaines: Planète et Univers [physics]; Géophysique [physics.geo-ph]

Vadim Monteiller, Stephen Beller, Bastien Plazolles, Sébastien Chevrot. On the validity of the planar wave approximation to compute synthetic seismograms of teleseismic body waves in a 3-D regional model. Geophysical Journal International, 2021, Geophysical Journal International, 224 (3), pp.2060-2076. ⟨10.1093/gji/ggaa570⟩. ⟨hal-03021049⟩