Inversion interpretation of CSAMT single-component data

Abstract

CSAMT always use MT to calculate the Cagniard resistivity which is the ratio of electric field component and magnetic field component. CSAMT field source is known and the electric field component and the magnetic field component have a certain relationship with the underground resistivity. Therefore the single-component date including magnetic field component or electric field component can be used to extract the apparent resistivity. In order to improve the influence of noise to data interpretation, the paper put forward that the single-component of CSAMT is used to calculate the apparent resistivity through analyzing the data quality of magnetic field component and electric field component. The generalized inverse matrix inversion method is used and the layer number equals to time channel. The method overcomes the problem that the layer number is low, and the fitting inversion of the apparent resistivity curve in the whole field is realized. The detection of the result of seeper mine-out area in Datong show that the single-component detection and interpretation method is effective. Keywords—CSAMT; inversion interpretation; single- component date I. INTRODUCTION Controlled Source Audio-frequency Magnetotellurics (CSAMT for short) has been applied in geological survey, metal minerals, geothermal, hydro-geology, environmental geology, coal geology and other exploration . The ratio of the electric field component and the magnetic field component is used to define the apparent resistivity of the CSAMT. Although the ratio of apparent resistivity may be offset by the same interference, it is likely that quality of the measured magnetic field and electric field are different and the interference effects are also different because the polarization direction of electromagnetic interference is different, the environment and geological conditions are different (such as the earth's electric field component can't be observed or the quality is not high). However, CSAMT emission current is known, and the single component electric field and magnetic field can be separated so that the interaction between the single component and the magnetic field is avoided. The single-component apparent resistivity of CSAMT is derived through uniform earth far zone. In order to get the apparent resistivity that has hierarchical capabilities and is whole region, iterative algorithm is widely used