Application Of Geomagnetism Gradient Sounding To Deep Structure Explotation

Studing area across the Bayan Har block and South China block, in the Tibetan Plateau of eastern edge Songpan-Garze orogenic belt, the Long men Shan and complexity of the coupling region Longmen Mountains foreland basin, and is an important component of China continental tectonic units section. At present, for exploration Long men tectonic belt,which is mainly perpendicular to the goal. In order to compensating for the Long men Shan exploration study defects, we select the parallel distributed in the Long men Shan implemented Gong ga Mountain-Du jiang yan(L70) survey line.The paper infers the geomagnetic gradient sounding forward and inversion theory derivation, and make the magnetic gradient sounding of forward and inversion the numerical simulation comparative analysis, getting the adaptive regularization inversion than bostick inversion is more close to the real model. Based on the theoretical model and actual data analysis verity the geomagnetic gradient sounding can be used for calibration magnetotelluric sounding data, and we have completed 2D nonlinear conjugate gradient inversion and structural analysis based on the geomagnetic gradient calibration magnetotelluric sounding data.This paper relies on "Longmen Shan structural belt deep geological survey project", by the adoption of geomagnetic gradient sounding(GDS) combined with a long period magnetotelluric(LMT), and use the Longmen Shan across the Gongga Mountain-Dujiangyan line 2D inversion processing of the data and structure of the resolution, combined with many across the Longmen Shan tectonic belt of the great research of electromagnetic section preliminary, then sets up along the Longmen Shan tectonic belt in the central south the section sells crust-mantle electrical structure model. For the first time, from southwest to northeast fine we divided the Longmen Shan tectonic belt in the southern section of the electrical structure of Luding crust-mantle block, high resistance of longmen south section of the "T" type of crust-mantle high resistance block, lower the stopband Dachuan crust-mantle, Longmen Shan middle crust-mantle high resistance and the northern section of Longmen Shan crust-mantle high resistance block. In addition, also found that the middle Longmen Shan crust-mantle to the shape of a high resistance to conical, down into the mantle wedge. The "Empty earthquake zone" crust-mantle longitudinal electrical structure is: by the mountains crust-mantle low stopband and serdang high resistance block. Dachuan crust-mantle is low stopband for two high resistance block between resistivity of cascade band, serdang high resistance of quasi 3D electrical structure is irregular elliptic ball high resistance, ellipsoid north east short axis, south west axial length, and the wedge shaped wedging in the Songpan-Garze plot, where is a circle around the relatively low resistance gradient zone. In addition, according to research "Empty earthquake zone" underground structure characteristics, the paper concluded that "the Lushan earthquake", is likely to be affected by the Tibetan Plateau eastern edge squeeze more likely to cause earthquakes.Through summary analysis of structural deformation in the Longmen Shan tectonic belt and its adjacent area, crust-mantle electrical structure, magmatic origin, the depth of the source and formation age, the relationship between their variation patterns are summarized. Various environmental conditions, lead different tectonic dynamic evolution model. From early indosinian intracontinental collision- fold-slippage orogenic movement began, Songpan-Garze slippage belt to the south and south west migration to push the embryonic form the Longmen Shan; Yanshan movement caused local melting of crust-mantle material flows to the surface in the large areas of the molten rock mass invasion and overflow, thus forming the shell flange acidic granite rock mass and dike; During Himalayan, Songpan-Garze slippage belt moved to the Longmen Shan nappe orogeny, eventually formed a now strike-slip thrust- in Longmen Shan nappe tectonic belt.