Mento Carlo Inversion of the 1D velocity and anisotropic model in the Juan de Fuca plate

Tian Feng, Thomas Bodin, & Lingsen Meng

Submitted August 15, 2016, SCEC Contribution #6845, 2016 SCEC Annual Meeting Poster #230

In this study, we demonstrate the advantage of the Monte Carlo method in solving 1D velocity models. In order to obtain accurate models, both velocity and anisotropy need to be accounted for in the inversion. However, the unknown number of layers of isotropic and anisotropic velocity separated by discontinuities makes it challenging to set up the model parameters. The number of parameters could also alter during the Monte Carlo search process, which controls the speed and resolution of inversion. The core of the Markov Chain Mento Calro (MCMC) inversion method is based on the Bayesian Law: p(m|d) = p(d|m) × p(m). In this work, we derive the velocity and anisotropic models from Rayleigh wave dispersion curves using the MCMC method. We conducted intensive synthetic tests to verify the accuracy of this method. We then apply this method to the Rayleigh dispersion curves observed at the Juan de Fuca Plate and obtain anisotropic 1D velocity models with reasonably high resolution. In comparison with SKS splitting observations, the overall mean spitting times predicted by the 1D model based on Rayleigh waves are smaller and the fast axis more concentrated. This phenomenon can be explained by the difference of path effects between the SKS waves and Rayleigh waves: The SKS phase samples the whole depth range from the core-mantle boundary to the receiver station. On the other hand, Rayleigh waves are mainly sensitive to the crustal and upper mantle structures beneath the receiver station. In our future work, similar analysis will be extended to other regions to potentially separate the contributions of shallow and deep anisotropy in the SKS splitting observations.

Key Words
Mento Carlo, anisotropy, Juan de Fuca Plate

Feng, T., Bodin, T., & Meng, L. (2016, 08). Mento Carlo Inversion of the 1D velocity and anisotropic model in the Juan de Fuca plate . Poster Presentation at 2016 SCEC Annual Meeting.

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