Eikonal equation-based earthquake location

Abstract

Fault is one of the most common manifestations of tectonic activities. The occurrence of earthquake accompanying sudden slip along the fault, sometimes causing catastrophic result to human society. Besides, faults also contribute significantly to landscape modification and resources mining. In order to get comprehensive understanding of faults, it is crucial to firstly gain perception of the geological structure for the whole area. Since earthquake location is necessary for any subsequent research on the seismic event, earthquake relocation methods play indispensable role because of its accuracy and efficiency. In fact, relocation methods can be applied to many other science disciplines and industries as well, such as petroleum resource exploration and nuclear weapon tests, since it provides much more information besides geological structures, such as events occurence time and historical sequence. However, many of the popular approaches used in seismic studies requires accurate seismic wave data, especially for the ray pathing, or comparatively sufficient understanding of the subsurface structure material properties based on the previous studies. We developed a new earthquake relocation method based on Eikonal equation, which efficiently bridges the gap between the background velocity model and the evolution of seismic wave front.The main parts of this thesis include brief introduction of earthquake location methods, introduction of mathematic principles of earthquake relocation, introduction and explanation of Eikonal-Equation based earthquake location method and its application in both synthetic and realistic catalog data. We also use fast marching method by grid searching and traveltime adjoint tomography method to improve the accuracy and correctness of the earthquake location.