MT探测居里面深度的可行性研究

居里面是地球内部铁磁性物质向顺磁性物质转换的界面，在温度略低于居里点时物质磁化率会快速升高，这被称为Hopkinsin峰.对于地球内部而言Hopkinsin峰是只有几百米至几公里厚的薄层，由于其与居里温度的关系，因此其底界面的深度可以作为居里面深度的估计.传统的居里面深度探测方法包括谱分析方法、等层模型方法和温度－深度剖面法.这些方法是人们研究地球内部热结构和居里面深度的重要手段，但是谱分析和等层模型的结果均有一些固有的缺点，如横向分辨率太低等；而地热方程的结果则受地表因素影响十分严重，并且地球内部的热源分布也不是十分清楚，这导致了其结果是不可靠的.本文提出用MT方法探测居里面深度，通过对几种简单一维模型进行的正反演数值试验，论证了该方法的可行性.结果表明，用MT方法研究居里面性质，不但可以得到居里面深度，还可以得到居里面顶部Hopkinsin峰所对应介质的电学和磁学性质，但必须同时反演岩层的电阻率和磁导率，才能获得较为可靠的居里面深度估计.

Study on the feasibility of using the MT method to map the depth of Curie interface

Curie-surface is a temperature dependent interface in the earth where the iron-magnetic mineral is realized to be lost its ferromagnetism. Modern physical experiments indicate that the magnetic susceptibility of rocks will be increased by several tens to hundreds times when the temperature is just below the Curie point. The conventional methods used in mapping the depth of temperature approaching to the Curie point are the spectral analysis and equivalent layer model based on geomagnetic data. But both of them have some inherent limitations. In the present study the feasibility of using the MT method to map the depth of Curie-surface was numerically investigated on the 1D earth model. The results show that the thickness of the abnormal magnetic layer can not be determined accurately; however, the depth to the layer and its electrical and magnetic properties are well resolved. This study hence provides a potential application for the classical magnetotelluric method.