【作者】 冉云；

【导师】 刘鸿福；

【作者基本信息】 太原理工大学 ， 地球探测与信息技术， 2010， 硕士

【摘要】 瞬变电磁法是一种利用电磁感应原理预测地下目标地质体的地球物理方法。因其具有受地形影响小、探测深度较大、穿透高阻能力强、工效高等特点,成为中浅层探测的重要方法之一。而对于瞬变电磁法观测数据的预处理及测区垂向电性层的划分,由于地质条件的复杂性,现有的方法中还存在一些有待探讨的问题。近年来在信号分析与处理领域,出现了较为先进的号称“数学显微镜”的小波分析数据处理方法。它是针对非平稳信号的处理方法,能够分辨正常信号中夹带的瞬态反常现象并展示其成分,比较适合于动态、瞬态的信号处理。而在瞬变电磁法工作中,得到的就是动态、瞬态的信号,因此引入小波分析对信号进行处理,可以提高瞬变电磁法解释精度。瞬变电磁法对地下低阻体的探测,具有较好的效果,而对目标体为高阻体的探测,尤其是对高阻体电性层的划分,研究程度不高,本文对此以采集的观测数据为基础,采用小波分析对原始数据进行滤波处理,并根据瞬变电磁场的晚期响应规律对感应电压衰减曲线再次进行斜率组合滤波,在保证数据原始变化趋势的前提下,得到了较为平滑的感应电压衰减曲线;最后根据信号预处理的效果,分析认为在单测点上,经过滤波后的曲线晚期段,第一个变幅较大突变点后的采集点数据应予以舍弃,不宜作为正常磁场响应参与反演解释。瞬变电磁观测数据的反演解释,通常采用视电阻率ρτ(t)曲线,而对视纵向电导参数sτ(t)曲线的反演用得较少,且主要用于低阻体的解释。本文选择目标体为高阻体,运用视纵向电导参数sτ(t)曲线对实测数据进行了较为详细的实际处理解读,并对横向、纵向的分辨率做了对比,得出运用两种曲线在横向、纵向上进行电性分辨的优势及局限性。通过实验,表明了视纵向电导测深曲线在对地层垂向电性层的划分中是可行的,详细研究曲线的细微变化特征在解决实际问题中具有一定的现实意义。更多还原

【Abstract】 Transient electromagnetic method, as a geophysical method, detects geological underground targets by electromagnetic induction. Refer to properties of less effect caused by terrain, greater depth of detection, stronger ability for penetrating the high impedance layer and higher work efficiency, it become one of the important methods for mid-shallow exploration. But for the preprocessing of transient electromagnetic data and corresponding vertical electrical layering, there remain some questions need to discuss due to complexity of geologic setting.The wavelet analysis, which was known as‘mathematical microscope’, emerged in the field of signal analysis and processing in recent years. It aims at non-stationary processing, so it is applicable to detect and show the components of transient anomalies entrained in normal signal, especially for dynamic and transient signal processing. Because of the signal obtained from transient electromagnetic method is exactly dynamic and transient, it becomes feasible to apply wavelet analysis for signal processing, in order to achieve the purpose of improving interpretation accuracy. Transient electromagnetic method is more applicable to detect a conductor underground, while for high resistivity bodies, especially to differentiate vertical electrical layer in such section, corresponding research has not attract enough attention. In this paper, wavelet transform is used for filtering data which was derived from detecting in the field, and then slope filtering applied to induced voltage attenuation curve according to late response law of transient electromagnetic. And in the premise of ensuring data original trend, smoother induced voltage attenuation curve can be obtained. At last, based on the effect of signal preprocessing, it believe that in the primary data, the corresponding data after the first variational point which has major amplitude on the curve should be abandon rather than participation as a normal response to the magnetic field inversion and interpretation.Apparent resistivity curveρτ(t) is commonly used in the transient electromagnetic data inversion and interpretation, but apparent vertical conductance parameter curve sτ(t) is seldom used, it mainly be applied to interpretation for conductor. In this paper, apparent vertical conductance parameter curve sτ(t) is used to deal with data in detail interpretation and processing, on account of the given target which is a high resistivity body. Then vertical with horizontal resolution comparison is followed. Finally, it discusses advantages and limitations of horizontal and vertical electrical resolution by using the two curves. The experiment shows that it is feasible to use apparent vertical conductance curve divides vertical strata electrical layer, and it has important practical significance for studying curve subtle changes in case of solving practical problems.更多还原