川西—藏东大地电磁资料的阻抗张量畸变分解

IMPEDANCE TENSOR DISTORTION DECOMPOSITION OF MAGNETOTELLURIC DATA FROM WEST SICHUAN-EAST XIZANG

根据Swift和Bahr的分解结果 ,得到准三维 二维模型的区域构造和各个畸变因子 ,应用于川西—藏东MT剖面资料的分析 ,结果表明 :该地区的构造特点为浅部比较简单 ,深部相对复杂 ;以雅安为界 ,东部构造比西部构造简单 ,而且比较稳定 ;构造主轴方位基本在近南北向 ,其偏差很少超过 30°;分解参数对几条大的断裂有较好的显示 ;测线 1横穿 3个主要构造单元 ,并被几条大断裂切割 ,构造最复杂 ;测线 2接近 3D 2D模型 ;测线 3具有较强的静位移畸变 .

We have obtained the regional structure of a quasi-3D/2D model and distortion factors from the result of Swift and Bahr's decomposition in analysis of magnetotelluric data of West Sichuan-East xizang sounding profiles. The result shows that the structure of the region along these profiles is simple in the shallow part and relatively complex in the deep part. Taking the Ya'an line as a boundary, we find that the structure in the eastern part is simpler and more stable than that in the western part. The orientation of major structural axis is basically in nearly S-N direction and its deviations are Seldom more than 30°. The decomposed parameters can well express several major faults. The first sounding line runs across 3 major tectonic units and several major faults, so the structure is most complex. The second sounding line is close to a 3D/2D model,and the third sounding line exhibits stronger static displacement distortion.