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Thursday, March 16 • 4:00pm - 5:30pm
Poster: Studying the Lithosphere–Asthenosphere Boundary beneath the Western United States by High-Resolution Seismic Filtering based on Non-Convex Regularization of Radon Transform

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The lithosphere-asthenosphere boundary (LAB) separates the rigid, cold lithosphere characterized by a conductive thermal regime from the underlying hot, convecting mantle asthenosphere. The LAB is also a rheological discontinuity that marks differential motion between tectonic plates and the underlying mantle, hence, studying this boundary will help us to understand plate motions, tectonics, and mantle convection. Ps and Sp phases that convert at the LAB are powerful tools to estimate the depth and the velocity gradient of the LAB, however, it is always been a challenge to study the LAB by Ps receiver functions due to interference of the primary conversions with strong crustal reverberations. In this study, we proposed a novel method to filter the crustal reverberations and to enhance the LAB signals based on non-convex regularization of Radon Transform. The Radon transfer sums signals exhibiting linear, parabolic or hyperbolic moveout in the original domain (t-Δ domain) to a single event in the new domain (Radon domain). Consequently in the Radon domain, the target signals can be isolated easily from the noise. To further enhance the spatial resolution in the Radon domain and decrease the computational cost, a pre-processing method was developed in our group based on the linear random transform in the frequency domain implemented with compressive sensing theory. The compressive sensing approach helps in recovering the sparsest solutions in the radon domain to underdetermined inverse problems. Instead of least square minimization, a non-convex minimization (Lp regularization with 0<p<1) is used to regularize the inverse problem. Our results show that at most only three iterations are needed for the non-convex minimization algorithm to reach the desired level of sparsity. Since non-convex regularized Radon Transform offers a benefit for signal isolation in Radon domain, this method can be a powerful tool to remove crustal multiples from Ps receiver functions and enable us to obtain better LAB images. Here, we show some results by applying this method to Ps receiver functions from broad-band seismic stations in USArray. For both synthetic and USArray receiver functions, the results clearly demonstrate that non-convex regularized Radon Transform can provide a superior reconstructed LAB image by filtering out the signals from crustal reverberations. We further propose to apply this method to reconstruct the common conversion point (CCP) stacked Ps and Sp receiver function images of the LAB beneath the western United States.

Speakers

Thursday March 16, 2017 4:00pm - 5:30pm
Exhibit Hall BRC