【作者】 余友；

【导师】 何继善；

【作者基本信息】 中南大学 ， 地球探测与信息技术， 2012， 博士

【摘要】 大地电磁测深(MT)和可控源大地电磁测深(CSAMT)是近几十年发展起来的电磁勘查方法,以其探测深度大而受到青睐。MT测深和CSAMT测深视电阻率曲线,其左支(前支)振荡地趋近于上部层电阻率,振荡的右端(低频端)有一个振幅最大的振荡峰值(但比非均匀大地视电阻率曲线的最大绝对值小很多),过去人们大多称它为“假极值”。也可以(如A.A.Kaufman和G.V.Keller)称之为“极值”并注意到其中含有的部分地电信息。“假极值”含有关于地电断面的比较信息,假极值不假!故本文将这一振幅最大峰值称为“小极值”。本研究是国家自然科学基金重大仪器专项广域电磁法研究的一部分,论文以大地电磁测深和可控源电磁测深的理论公式为基础,以二层、三层及四层断面为例,编程计算了一系列不同断面类型、不同地电参数的视电阻率曲线。通过正演模拟,比较、分析了上述小极值的出现频率、曲线特征、幅度大小与断面参数的关系,发现小极值的这些特征含有关于地电断面参数的比较丰富的信息。对于简单的地电构造(如二层断面),根据视电阻率曲线的左支(前支)渐近线和小极值特征,能够提取到关于断面参数的全部信息。对于比较复杂的地电构造(如三层甚至更多层断面),根据视电阻率曲线的左支(前支)渐近线和小极值特征,能够提取到关于断面上部的部分参数信息,为提取全部断面信息提供有力的约束条件,提高解释的准确性和稳定性。给出了提取上述信息的具体方法。本文关于“假极值不假”,应该称之为“小极值”的观点,关于小极值特征含有地电断面丰富信息的观点以及提取断面信息的具体方法,是一种新的尝试。充分利用MT和CSAMT测深视电阻率曲线左支(前支)和小极值特征,在电磁法勘探的野外工作和室内解释中具有非常重要的实用价值和经济意义。对于简单的地电构造(如二层断面),能够在少观测(或不观测)视电阻率曲线低频段的条件下,获得断面的全部参数信息,大大减少野外观测和室内解释的工作量,节省时间和成本,提高工作效率和经济效益。对于较为复杂的地电构造(如三层或更多层断面),能够在缺少视电阻率曲线低频特征的前提下,利用视电阻率曲线左支(前支)和小极值特征,较可靠地获得断面上部的若干信息,为获取断面全部信息提供有力的约束条件,减少推断解释的未知因素,提高解释的准确性和稳定性,节省时间,提高效率。最后通过实例与前人作出的解释和钻井控制的地质断面相比得出利用极值特征作出的解释效果理想。更多还原

【Abstract】 Magnetotelluric sounding (MT) and controlled source magnetotelluric sounding (CSAMT) electromagnetic exploration methods developed in recent decades, with its probing depth favored. MT sounding and CSAMT sounding apparent resistivity curve, the left branch (anterior branch) oscillation close to the upper layer resistivity (than the non-uniform earth, as the right end of the (low-frequency oscillation end) with a maximum amplitude of the oscillation peak the maximum absolute value of the resistivity curve is much smaller), in the past most people call it "false extrema.(Such as AAKaufman and GVKeller) called "extreme" and can also notice containing partially electrical information. The "false extrema contain comparative information about the geoelectric section not fake, false extrema In this paper, it is that the amplitude of the largest peak called "small extremal.This study is part of a study of the major instrument special WAN electromagnetic method of the National Natural Science Foundation of paper magnetotelluric sounding and controlled source electromagnetic sounding theory formula-based, two-story, three-and four-cross section, for example, programmed to calculate a range of different cross-section types, the apparent resistivity curves of different electrical parameters. By forward modeling, comparing, analyzing the relationship between the frequency of occurrence of the extremum curve characteristics, the magnitude of the margin, and section parameters and found that these characteristics of the small extremum contains information about the parameters of the geoelectric section. Simple ground structure (such as the two-story section), the asymptote (former support) and small extremal characterized under the left branch of the apparent resistivity curve, able to extract all the information about the profile parameters. Complex ground structure (such as three or more layer cross-section), according to the left branch of the apparent resistivity curve (former support) asymptote and small extremal characteristics, able to extract some parameters on the upper part of sectional provide strong constraints to extract all the cross-section information, to improve the accuracy and stability of interpretation. Specific methods of extraction of the above information is given.This article about the false extrema false, it should be called "extreme" point of view, about the characteristics of small extremal contains the geoelectric section rich view of the information and the specific method to extract the cross-section information, a new attempt.Make full use of the MT and CSAMT sounding apparent resistivity curve left branch (anterior branch) and small extremal characteristics, has a very important practical value and economic significance in the the electromagnetic exploration field work and the indoor explain. For simple electrically configured (e.g. Layer sectional), it is possible in a small observation (or observation) under conditions of low band of apparent resistivity curves obtained all the parameter information of the cross-sectional, greatly reducing the workload of the field observation and laboratory interpretation save time and cost, and improve work efficiency and economic benefits. For more complex ground structure (such as three or more layers sectional), in the absence of apparent resistivity the curve low frequency characteristics premise, the apparent resistivity curve left branch (anterior branch) and small extremal characteristics, more reliable and access to a number of cross-section upper information, provide strong constraints to obtain cross-section all information, reduce the unknown factors of inference and interpretation, and to improve the accuracy and stability of interpretation, save time and improve efficiency. Finally, compared to the explanations given by example with the previous geological cross-section and drilling control come to the satisfactory results of the explanations given by the extreme value characteristics.更多还原