【作者】 孟银生；

【导师】 姚长利；

【作者基本信息】 中国地质大学（北京） ， 地球探测与信息技术， 2010， 硕士

【摘要】 可控源音频大地电磁法(CSAMT)是在大地电磁法(MT)和音频大地电磁法(AMT)基础上发展起来的一种人工发射源电磁测深方法。MT利用电离层场源激发的电磁波作为入射信号,AMT利用雷电激发的电磁波作为入射信号,二者不需要庞大的发射源设备,施工设备比较轻便。由于激发源的问题,MT和AMT观测信号弱且采集数据时叠加时间较长,同时不能很好压制工业和来自空中的电性干扰,从而促使有较强抗干扰能力的、采用人工场源通过改变频率来进行测深的地球物理方法的出现。1971年在加拿大多伦多大学,这种抗干扰较好且叠加速度较快的勘探方法(即CSAMT)应运而生。CSAMT的应用范围很广,在对矿山、地热、水资源、油气等的勘探工作中都可以发挥作用,并取得了良好的效果。然而MT法中原本就有的静态位移问题(也称静态效应)在CSAMT中同样存在,是困扰CSAMT处理和解释的几大难题之一严重影响着勘探结果的可信度。因此,对CSAMT资料进行静态校正就成了处理解释的不可缺少的步骤。要进行静位移校正需要先弄清楚静位移现象产生的物理和数学本质。由于在近地表存在小规模的电性不均匀体使得地下介质中的电流分布产生畸变,从而使得地面电场观测值出现一个向上或者向下曲线形态保持不变的移动,而相位曲线和磁场曲线不变,进而导致视电阻率曲线沿着电阻率轴线也产生了形态不变的向上或者向下位移。本文根据麦克斯韦方程组结合边界条件,分析了静位移的产生机制,并编制程序进行静位移的正演、静位移的识别以及静位移校正的研究。要进行静位移校正,首先要能正确识别数据中是否含有静位移效应(需区分异常数据和静位移效应),然后根据实际情况选择合理的校正方法对数据进行静校正。国内外文献资料表明,目前静校正方法主要有空间滤波法、中值滤波法、曲线平移法、相位法、磁场数据推算法、小波分析法等。本论文通过模型实验证明中值滤波法和曲线平移法得到的静位移校正结果较为理想。大部分时候静位移对我们的勘探工作是有害的,需要对静位移进行校正,以消除静位移效应的干扰。同时,静位移现象亦是一种对浅层导致电性不均匀地质体的一种勘探方法,在此仅作理论探讨。静位移现象的实际资料处理,选择某铜矿附近的CSAMT实测数据,其中有某地段静位移现象比较严重。通过静位移校正处理,有效地消除了静位移效应(该区为地表低阻引起的静态位移),避免了将某些静位移效应解释为深大断裂产生的异常。更多还原

【Abstract】 Controlled source audio frequency magnetotelluric method (CSAMT) developed on the basis of the magnetotelluric method (MT) and audio frequency magnetotelluric method (AMT) is an artificial emission source electromagnetic sounding method.MT field source using the ionosphere as the incident electromagnetic wave excitation signal, AMT make use of lightning as the incoming electromagnetic wave excitation signal, the two do not need a large emission source equipment, the equipment more portable. As the excitation source is weak, MT and AMT observations are small too. Collecting data need long superimposed time, while not suppress the industrial electricity and electrical interference from the air, thus contributing to find a geophysical methods that has strong anti-jamming capability, which using controlled source and by changing the frequency for sounding. University of Toronto in Canada in 1971, this interference better and faster exploration stacking methods (namely CSAMT) came into being.CSAMT has a wide range of applications, in the mining, geothermal, water, oil and gas exploration work in a role to play, and have achieved good results. However, MT originally had a static displacement problem (also called static effects) also exists in CSAMT, it became one of several major problems in CSAMT processing and interpretation, seriously affecting the credibility of the exploration results. Therefore, the static correction in CSAMT data processing and interpretation has become an indispensable step.Static shift correction needs to be clear the physical nature of the phenomenon that produced static displacement. As there is the small-scale electrical heterogeneity near-surface, the current distribution underground media distorted, making the ground field observations curve displaced up or down with the same shape, while the phase curve of the same, leading to apparent resistivity curves change in same form of upward or downward displacement along the resistivity axis. This combination of Maxwell’s equations under the boundary conditions, analysis of the static displacement mechanism for the generation and use program demonstrates static shift forward, static shift identification and the correction of static displacement. The static displacement correction should firstly to correctly identify whether it contains static displacement data (abnormal data and the static effect should be distinguished), then choose the reasonable correction method to correct the data. Domestic and foreign literature data indicate that static shift correction methods are curves translation, spatial filtering, median filtering, the phase method, the magnetic field measured data calculate the resistivity, wavelet analysis method. The paper show by model median filtering and curves translation correction is the ideal result.Most of the time, static displacement in our exploration work is harmful. The static correction to eliminate the interference of the static displacement is needed. In some cases, such as theory researching, Static displacement may also be an better exploration method in exploring the non-uniform electric properties of shallow geological, in which only a theoretical study.In practical CSAMT data processing, select the CSAMT data near a copper mine, including the phenomenon of static shift of a lot more serious. Static correction eliminate the static effect effectively (low resistivity caused the static displacement in the area), avoids some of the static shift effect interpreted as resulting from abnormal deep faults.更多还原