Open AccessElastic full‐waveform inversion for earthquake source parameters
Author(s) -
Wu Yafei,
McMechan George A.
Publication year - 1996
Publication title -
geophysical journal international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0956-540X
DOI - 10.1111/j.1365-246x.1996.tb01535.x
Subject(s) - amplitude , extrapolation , superposition principle , maxima and minima , a priori and a posteriori , geology , seismogram , smoothing , inverse problem , inversion (geology) , spurious relationship , jacobian matrix and determinant , mathematical analysis , geodesy , earthquake location , geometry , mathematics , seismology , physics , optics , induced seismicity , philosophy , statistics , epistemology , tectonics
2‐D full‐waveform inversion of double‐couple earthquake sources is implemented. Temporally and spatially extended sources are represented by superposition of double‐couples. The source parameters solved for are the spatial location, origin time, amplitude and orientation of each double‐couple. The velocity and density distribution and source time function are assumed to be known a priori but may be arbitrarily complicated. The non‐linear inverse problem is solved by iterative linear approximation. The Jacobian matrix elements for source depth and rupture angle are computed by wavefield extrapolation forward in time, while those for origin time and amplitude are computed analytically. A smoothing technique that results in faster convergence and avoids local minima associated with cycle skipping is applied at each iteration. A spatial sampling interval, between discrete sources, of one‐quarter wavelength of the dominant shear wave is optimal for inversion if high uniqueness of the result is desired. The presence of a fault is inferred from the spatial continuity of the rupture solution, rather than being imposed a priori. The method is illustrated by successful application to three synthetic source models: a single double‐couple, a single extended rupture and a double extended rupture. The resolutions of the source depth and origin time are higher, and their posterior covariances are lower than those of the amplitude and rupture angle at each source point. Source depth, origin time and amplitude are primarily determined by the data; the rupture angle is more strongly influenced by the a priori information.