Spherical-earth Fréchet sensitivity kernels

Tarje Nissen-Meyer (1) , F. A. Dahlen (1) , Alexandre Fournier (2)

1 Department of Geosciences [Princeton]
2 LGIT - Laboratoire de Géophysique Interne et Tectonophysique

We outline a method that enables the efficient computation of exact Fréchet sensitivity kernels for a non-gravitating 3-D spherical earth model. The crux of the method is a 2-D weak formulation for determining the 3-D elastodynamic response of the earth model to both a moment-tensor and a point-force source. The sources are decomposed into their monopole, dipole and quadrupole constituents, with known azimuthal radiation patterns. The full 3-D response and, therefore, the 3-D waveform sensitivity kernel for an arbitrary source–receiver geometry, can be reconstructed from a series of six independent 2-D solutions, which may be obtained using a spectral-element or other mesh-based numerical method on a 2-D, planar, semicircular domain. This divide-and-conquer, 3-D to 2-D reduction strategy can be used to compute sensitivity kernels for any seismic phase, including grazing and diffracted waves, at relatively low computational cost.

Mots clés: Fréchet derivatives; global seismology; normal modes; numerical techniques; perturbation methods; seismic-wave propagation

Domaines: Planète et Univers [physics]

Tarje Nissen-Meyer, F. A. Dahlen, Alexandre Fournier. Spherical-earth Fréchet sensitivity kernels. Geophysical Journal International, 2007, 168 (3), pp.1051 à 1066. ⟨10.1111/j.1365-246X.2006.03123.x⟩. ⟨insu-00347499⟩