大地电磁测深“降维逼近法”二维反演

本文提出了一种新的二维MT反演方法－－“降维逼近法”。该方法将每次二维反演迭代分解为二维正演和每个测点的精确一维反演两个过程。因此，在算法过程中避免了偏导数矩阵求解和大型反演方程组求逆两大难题，同时，每次迭代只需一次二维正演，从而加快了反演速度，模型试验表明，该方法是一种稳定收敛、实用有较为精确的方法。降维逼近法反演的最大横向分辨率等同于MT测点点距，纵向分辨率最大限度地体现了观测数据所能反映的构造分辨率。在MT固有的等值性范围内，降维逼近法能较好地恢复地下电性构造的形态。理论和实践都表明，该反演方法比同步阵列大地电磁测深（SAMT）和连续电磁剖面法（CEMP）等MT方法的效果更佳。

2-D inversion of magnetotelluric (MT) sounding data by dimension-descending approaching method.

The paper presented a new 2 D MT inversion method-dimension descending method,which divided each 2 D inversion iteration into two process:a 2 D forward problem and precise 1 D inversion for each survey point,avoiding two difficult problems in calculating process: solving the partial derivative matrix and calculating the inverse of large scale set of inversion equations and speeding up the inversion because of only one 2 D forward calculating for each iteration.The model tests show that the method is a stable convergent,practical and more precise method.Its maximum horizontal resolution is equal to the distance between adjacent MT survey points while vertical resolution can maximally reflect the structural resolution that the survey data can do.The method can better restore the geo electric structural attitude in a scope of MT intrinsic equivalence.The theory and the practice show that the inversion method has better results than synchronized array MT sounding (SAMT) and continuous electromagnetic profiling(CEMP).