Seismic traveltime tomography using earthquakes in study domain and stations at teleseismic distances

Teleseismic tomography is an important technique to investigate the 3-D crust and mantle structures of the Earth. Although teleseismic tomography has been successfully applied to image subsurface structures of tectonic zones with the relatively well distribution of stations, it is difficult to study the crust and mantle structures in some tectonic zones with a scarcity of seismic stations. In order to perform teleseismic tomography in such zones, we conducted a teleseismic tomography method by employing a new observation system. We transform the traditional observation system into the new one based on the reciprocity theorem. The traditional observation system of teleseismic tomography relies on seismic waves excited by teleseismic earthquakes around the study area and seismic signals recorded by stations in the study area. While the new observation system is that regional earthquakes inside the study area excite seismic waves and stations outside the study area at teleseismic distances record seismic signals. The article mainly contains three parts. First, we introduce the main principles and the processes of the application of the new teleseismic tomography method. Second, we analyze three influencing factors, which are ray coverage, picking error and source uncertainty. Third, we apply the new teleseismic tomography method to the Japan subduction zone by the inversion of real seismic traveltime data, and obtain the upper mantle velocity structure of the subduction zone. This real data tomography demonstrates the effectiveness of the developed method in this article.