【作者】 韩自豪；

【导师】 魏文博；

【作者基本信息】 中国地质大学（北京） ， 地球探测与信息技术， 2009， 博士

【摘要】 瞬变电磁法是寻找各种矿产资源及为工程、环境、水文地质服务的一种重要物探方法。目前瞬变电磁勘探主要应用二次磁场垂直分量,但当前多数瞬变电磁仪器均可实现三分量同时采集,由于缺少水平分量的解释理论及程序,水平分量数据无法进行解释,导致了巨大的、也是不必要的信息浪费。多分量、多种方法联合反演可以尽可能多的利用已知信息,得到最真实的地电断面,水平分量的研究可以为多分量联合反演提供一定的基础,最低限度也可以利用水平分量的特征点对地下三维体的形态给出定性的描述,为三维反演提供约束条件,提高反演速度。为此,论文针对磁性发射源瞬变电磁感应的水平分量进行了较为系统的研究,取得以下几个方面的研究成果:通过均匀半空间磁偶源瞬变电磁场各磁场分量的解析表达式,说明二次磁场水平分量比垂直分量对低阻体反映更敏感;计算分析了矩形发射回线中激励场的分布情况,指出地质体与发射源、接收线圈的位置关系影响观测结果,水平分量观测中要注意避开无激励角及无响应角;对传统的“烟圈”理论提出新的假设,认为在均匀半空间及水平层状介质中“烟圈”以与发射框“同形共轴”形态向下传播,推导出矩形“烟圈”各磁场分量响应的计算公式,并利用该公式计算了导电均匀半空间瞬变电磁场的水平分量,分析了响应特征,为生产中水平分量异常特征的认识和解释提供了依据。对瞬变电磁时域有限差分正演模拟,推导了各边界上Mur吸收边界条件,利用磁偶源在均匀半空间的瞬变电磁场解析表达式,将场源化为初始条件,模拟了均匀半空间及三维低阻体在均匀半空间的瞬变磁场水平分量,以图件展示了磁场水平分量在地下的扩散规律。资料显示,在低阻体中,瞬变电磁场传播速度变慢,因而对低阻体有更高的分辨率;直角坐标系下两个正交方向的水平分量对三维异常地质体有不同的分辨率和异常反映,平面图上,利用平行于三维体走向的分量对三维异常体横向边界识别更容易。实际生产中,对于大回线源工作装置,可以利用“烟圈”理论或FDTD三维正演模拟,得出均匀半空间或水平层状介质的标准响应,与实测结果相减得到类似于中心回线装置的水平分量“纯异常场”,方便资料的认识与解译。最后结合前述成果,对一个测区的瞬变电磁资料进行了三分量综合解释,比单一的垂直分量解释得到了更多的、更可靠的地质信息,为地质任务的完成提供了更充分依据。更多还原

【Abstract】 After the development of several decades, transient electromagnetic (TEM) method has become an important geophysical exploration method in finding mineral resources, as well as in engineering, environmental and hydrological services. In real TEM exploration, vertical-component of transient electromagnetic field is usually adopted. Most of the modern TEM equipment can acquire 3-component data synchronously, because of the absence of the interpretation theory and software, the horizontal data cannot be used, vast useful information is wasted unnecessarily. Multi-component, multi-method inversion can apply the known information as much as possible. The most true geoelectric section can be expected if multi-component, multi-method inversion is applied. The horizontal-component study can be useful to multi-component inversion, at least we can get some qualitative description of the 3-D objects under the surface, we can speedup the 3-D inversion by using the constraint conditions got from the horizontal-component study. In this dissertation, the study was focused on the horizontal-component responses of the magnetic sources TEM. The main results of the study are as below:It can be known that the horizontal-component is more sensitive to the conductive objects than the vertical-component from the respective expressions for the components. The exciting-field distribution of the rectangle transmitter loop was calculated and analyzed. The locations relation among the target object, the transmitter source and the receiver coil has important influence on the observed results. The non-exciting-angle and non-response-angle positions must be avoided when horizontal-component data are observed. A new hypothesis was introduced to the traditional“smoke ring”theory, that the“smoke ring”would diffuse downwards with the same shape of the transmitter loop and co-axial with the loop in uniform half-space or horizontally stratified medium. The formulas for calculating the magnetic field response with rectangle“smoke ring”were provided. The horizontal-component response was calculated using the formulas forementioned, this may be the foundation to the horizontal-component interpretation. When conduct time domain finite difference method (FDTD) program, the Mur boundary conditions were used to every truncation side, and the exciting source was transformed into initial conditions by using the accurate expressions of the components of TEM field in uniform half-space. The horizontal-component responses were simulated for half-space and for a 3-D conductive object in half-space. The figures tell us how the horizontal-component fields propagate under the surface of the earth. The results show that: the TEM wave travel slower in conductive objects than in resistive objects, so the TEM method has higher resolution for conductive objects exploration; for the same 3-D object, the two horizontal components have different resolutions and different anomalous characteristics, the component parallel to the long side of the 3-D object has clearer show to the transverse boundary.For fixed-loop source TEM, the pure anomalous data can be obtained using the data observed in field detract the standard response data which can be computed by applying“smoke ring”theory or conducting FDTD program. The pure anomalous data is easily to be interpreted. At last, a real case was demonstrated. The 3-component data was used to get more useful geological information. The results show the horizontal-component is helpful for the accomplishment of the geological task.更多还原