基于磁异常的边界特征增强方法对比研究

基于磁异常进行场源边界识别(如断裂划分)是磁法勘探解释工作的重要内容.由于受到斜磁化、场源埋深、异常叠加以及噪声等多种因素的影响,基于磁异常直接进行场源的边界识别往往难以准确识别出场源体的边界,所以,人们研究了各种场源边界特征增强的方法技术,以便于进行场源边界的识别工作.近年来,国内外出现了很多新的边界特征增强方法,但有些方法的边界特征增强效果与已有方法相近,有的方法效果有待深化检验,存在验证方法的理论模型过于简单,未全面细致地分析出它们的优缺点等问题.针对上述情况,本文运用多种复杂、贴近实际的理论模型,深入对比分析了包括解析信号模法和倾斜角法等在内的15种具有代表性的边界增强方法,分析了它们在不同磁化方向、不同场源埋深、不同场源形态、异常叠加和噪声干扰等多种因素影响下的边界增强效果,重点归纳总结出它们的优缺点和适用条件,以为实际应用时的方法选择提供参考.通过模型实验,我们认为解析信号模垂向导数法、总水平导数法、解析信号模倾斜角法是在多种因素影响下,适用性较强、应用效果较好的三种方法.

Comparative study on methods of edge enhancement of magnetic anomalies

Edge detection is a common means in magnetic data processing and interpretation, and can be used to locate geological boundaries such as contacts and faults. However, it is usually hard to accurately detect the edge location of a geological body by using magnetic anomalies directly due to the oblique magnetization and buried-depth of the source. To overcome this difficulty, researchers have developed various methods for edge enhancement in recent years. Nevertheless, little research was been done to systematically analyze the strengths and weaknesses of these different kinds of methods.#br#In order to choose appropriate methods that can be applied to interpretation of real data, we need to compare several potential methods and evaluate their effectiveness and application conditions. To achieve this aim, we first choose and compare 15 representative methods for edge enhancement, including analytic signal amplitude, tilt angle, and total horizontal derivative, which are either popular in practical application in the past or just proposed recently. Then, we analyze and summarize the fundamental principle and feasibility of each method. And finally we obtain the advantages and disadvantages of these methods through six synthetic model tests, from which we draw some conclusions as that (1) the methods that use high order derivatives have more powerful data resolution but are also more sensitive to noise, (2) all the chosen methods are affected by oblique magnetization of the source but several among these methods, including analytic signal amplitude, are less sensitive to the magnetization, and (3) those methods with depth normalization included are less susceptive to the buried-depth of the source, however they will very likely produce false values which may disturb edge detection.#br#The comprehensive comparison of these methods in our research shows that vertical derivative of analytic signal amplitude, total horizontal derivative, and tilt angle of analytical signal amplitude are the best three methods in practical application.