3D first-arrival traveltime tomography with linearized eikonal equation and shaping regularization
Yang Guoquan1,2, Ding Pengcheng1,2, Li Zhenchun1,2, Zhang Kai1,2, Wang Chong1,2
1. School of Geosciences, China University of Petroleum(East China), Qingdao, Shandong 266580, China;
2. Function Laboratory of Marine Geo-resource Evaluation and Exploration Technology, National Marine Laboratory, Qingdao, Shandong 266071, China
Abstract：First-arrival traveltime tomography is an important tool for estimating near-surface long-wavenumber seismic velocities.However,conventional algorithms utilized for traveltime tomography usually encounter problems when handling large 3D seismic data.For instance the raytracing has low computational efficiency and instability when strong velocity contrast exists in velocity models,and conventional regularization algorithms lie in their low iterative convergence rate caused by the insufficient control on models estimated by Tikhonov's regularization,which could be detrimental for large 3D scale problems,when only very few iterations are affordable.Therefore,on the basis of linearized eikonal equation,we propose a new algorithm to calculate the Fréchet derivative matrix with the upwind differences scheme without using cumbersome raytracing.Additionally,we incorporate a shaping regularization into conjugate gradient algorithm to iteratively minimize the data misfit.Finally,numerical experiments on 3D models demonstrate that the proposed algorithm has higher accuracy and faster convergence compared with the conventional algorithms.
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