The indepth magnetotelluric experiment on the Tibetan Plateau and its implications

Abstract

This dissertation focus on the application of the magnetotelluric method to tectonic studies on the Tibetan Plateau. The framework of this thesis composes three parts. The first part concentrates on magnetotelluric data inversion in the presence of strong topographic or bathymetric distortions. A new approach is described to invert magnetotelluric data with strong topographic distortions and a few examples are shown to demonstrate the capability of this algorithm. The second part of this dissertation illustrates how magnetotelluric data can be used to constrain the nature of the conductive middle crustal zone in southern Tibet. Seismic bright spots have been identified in the middle crust of southern Tibet, but the nature of these bright spots can not be resolved by seismic data alone. Using minimum conductance derived from magnetotelluric data, important thickness constraints are developed for the middle crustal conductive zone. Combining these constraints with other geophysical data, the seismic bright spots in southern Tibet may be best explained by a thin layer of aqueous fluid overlaying a thick partially molten system. Study of the electrical structures in central Tibet is presented in part three. High regional conductance is observed in central Tibet and the best candidate for the high conductance is partial melt. The dissertation ends with main conclusions from these studies.