Abstract: As a part of the EMSLAB project,the principal purpose of the study is to provide the constraints on electrical structures of the lithosphere and asthenosphere beneath Juan de Fuca plate and its vicinity.We have carried out two-dimensional modelling of the magnetotelluric data provided by EMSLAB group. One-dimensional method has been used in inversion,and then finite clement method used in two-dimensional modelling. The known superficial features are determined at various stages of the modelling. In order to confirm the uniqueness of the model,we have changed some important parameters of the model and assessed the increase of misfit.The model with best-fitting data shows that the lithosphere of the Juan de Fuca plate is a resistive layer with a thickness of about 40km,which is thinner than that of the older plate. The thickness of the asthenosphere is about 60km,underlain by less resistive layer overlapping a conductive half space.

Key words: Juan de Fuca plate, Rotation of impedance tensor, Inversion by layer model, 2-D modelling, Electricity layer

摘要： 本研究做为电磁感应国际合作研究项目—EMSLAB计划的一部分,主要目的在于确定东太平洋年轻的海洋板块——JuandeFuca板块及其周围地区岩石圈和软流圈的电性结构。在对海底观测的大地电磁资料定性和定量分析的基础上,进行了二维数学模拟。在二维模型中,海洋地形和已知的表层构造被确定。通过改变模型的重要参数,评价响应函数和观测资料之间偏差的增加,检验模型的可靠性。结果表明,JuandeFuca板块深部存在两个导电层,一个在40km,另一个在200km左右。这里岩石圈比其它较老板块的岩石圈薄。

关键词: Juan de Fuca板块, 阻抗旋转, 层状模型反演, 二维模拟导电层和电阻层