Abstract: Based on the observation data from 52 MT stations, this paper deals with the change of lateral electric property in crust-upper mantle in partial region of Northwest China. According to the depth of upper interface of the first low resistivity layer in upper mantle, the interesting region can be devided to four kinds of areas: shallow(depth of 55-90km), medium-shallow(90-110km), medium-deep(110-160km) and deep(160-250km).The electric property at depth associated with 6 great earthquake cases is discussed also. The results indicate that the area with steep gradient zone of the top of upper mantle, the area with evident change of lateral electric property in crust, and the area with particularly thickened low resistivity layer in crust may be considered as potential earthquake areas.

Key words: Northwest China, Megnetotelluric sounding, Crust, Upper mantle, Resistivity layer, Earthquake

摘要： 由50余个测点的大地电磁测深资料,讨论了该区的地壳-上地幔电性横向变化特征。按照上地幔第一低阻层顶面埋深,将测区划分为四类地区:浅埋深(55-90公里)、中浅埋深(90-110公里)、中深埋深(110-160公里)和深埋深(160-250公里)。讨论了本区六次大震例的深部电性背景。指出了上地幔顶部的梯度带地区、地壳内电性横向变化剧烈的地区和地壳内存在局部特殊增厚的低阻层地区将可以作为潜在震源区的深部电性判据之一。

关键词: 中国西北地区, 大地电磁测深, 地壳, 上地幔, 电阻层, 地震