The Earthquake Location And Seismic Tomography Based On The Waveform Inversion

Earthquake location and seismic tomography are fundamental and important seis-mic inverse problems.With the rapid development of computing power and numerical algorithm in recent years,it becomes more and more popular to invert the earth's inte-rior structure by the direct simulation of seismic wave propagation.Compared to the ray-based inversion methods,the waveform inversion methods avoid the high-frequency assumption.This means that it is possible to obtain high-resolution inversion results from the new methods,making the waveform inversion methods a key research direction in seismology.This thesis discusses the techniques to solve the problems of high computational cost,small convergence domain,and low location accuracy of the traditional waveform-based earthquake location method.Under the₂measure,we discuss the optimal selection of origin time and stations during iterations to greatly expand the convergence domain.We also propose the auxiliary function method to locate the earthquake efficiently and globally.We successfully applied the Wasserstein metric from Optimal Transport theory to the earthquake location problem,which significantly improves the convexity of the objective optimization function and reduces the impact of noise.The Wasserstein-Fisher-Rao metric from unbalanced Optimal Transport theory is further applied to the earthquake location problem,which overcomes the degeneracy of the objective optimization function near the optimal solution.Finally,we present a local earthquake tomography to illuminate the crustal and up-permost mantle structure beneath the southern Puna plateau.The imaging results provide essential evidence to the delamination hypothesis of the southern Puna plateau.It helps us to understand the occurrence and evolution of this lithosphere delamination deeply.