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Parametric Analysis of a Nonlinear Least Squares Optimization-based Anelastic Full Waveform Inversion Method

Aysegul Askan, Volkan Akcelik, Jacobo Bielak, & Omar Ghattas

In Preparation 2007, SCEC Contribution #1132

In a recent article, we described an inverse anelastic wave propagation method for determining the crustal velocity and attenuation properties of basins in earthquake-prone regions. We formulated the inverse problem as a constrained nonlinear least squares optimization problem in which the constraints are the partial (PDE) and the ordinary (ODE) differential equations describing anelastic wave propagation from source to receivers. In this paper, we present additional details of the solution technique and we conduct a parametric study to investigate the influence of a number of parameters on the inversion method including the form of regularization function, the value of the regularization parameter, receiver density, preconditioning, noise level of the data, and the multilevel continuation technique. We study the effects of these parameters on both the cost and quality of the inversion. The influence of these parameters is demonstrated through synthetic inversions for the shear wave velocity distribution in a two-dimensional anelastic medium, with the intrinsic attenuation expressed as a function of the seismic velocity. For the target shear wave velocity profile, we use a cross section of the shear wave velocity distribution for a sedimentary soil medium within the Los Angeles basin obtained from the Southern California Earthquake Center (SCEC) Community Velocity Model.

Askan, A., Akcelik, V., Bielak, J., & Ghattas, O. (2007). Parametric Analysis of a Nonlinear Least Squares Optimization-based Anelastic Full Waveform Inversion Method. Geophysical Journal International, (in preparation).