Time-domain Airborne Electromagnetic Data Analysis And Research In Tau-domain

AEM (Airborne Electromagnetic, referred AEM) is an airborne geophysicalsurvey methods based on the law of electromagnetic, by aircraft carriers. It has aflight fast speed, covering a large area, high efficiency, low cost, and many other goodadvantages, especially in mountainous terrain is more complex, such as no man’s land.But there are also some disadvantages, such as by different electromagnetic emissioncurrent waveform data are not receiving the same time characteristic; follow-up tablemethod Conductivity depth imaging class does not have the versatility; due to largevolumes of data processing and interpretation of the slow pace of other issues.In this paper, based on the classical theory of knowledge airborne electromagneticmethod, decomposed time-domain airborne electromagnetic data in Tau domain; andbased on this analysis, calculated the conductive limit and resistive limit in a varietyof earth model electromagnetic data, and analyzed the influencing factors; researchedthe Tau domain analysis applications in airborne electromagnetic; designed to achievethe Tau domain electromagnetic data analysis software platform, the content andconclusions of this paper are as follows:First, starting from the Maxwell equations, given an arbitrary emission currentone-dimensional forward modeling; using singular value decomposition of theairborne electromagnetic data illustrate the significance of Tau domain decompositionparameters A and; describes the Tau domain decomposition eigen-vectors, Finally,a variety of airborne electromagnetic data were analyzed in Tau domain. By analyzingthe results: With the increasing conductivity of the earth’s electromagnetic fields inthe data, Tau decomposed coefficient A’s larger value to the distribution direction ofmovement and reduced the amplitude of the energy dispersion.Secondly, based on Tau domain analysis, gave the concept of conductive limit andresistive limit from frequency domain and time domain, studied the conductive limit and resistive limit in a variety of earth model electromagnetic data; analyzed theinfluencing factors conductive limit and resistive limit. It got the results by analyzingthat conductive limit only is relation with the geometry of the target body, not to theconductivity of the target body; resistive limit is not relation with the target body,instead increased with increasing conductivity, while it independent of the geometryof the body, this rule provides a theoretical basis for the fast approximate inversion.Again, study Tau domain analysis applications in electromagnetic exploration.Use Tau domain decomposition removing the influence of emission current toelectromagnetic data. Use Tau domain decomposition of eigen-vectors to analyze theeffects of emission current pulse waveform to detection capability of the system has acertain significance for the rational design of the emission current. By analyzing theresults are that with increasing width of the transmitted waveform, eigen-vectorsdirection of the overall value to the larger Tau, indicating when the emission currentpulse width increases, the enhanced support for large conductivity anomaly resolutioncapability, so that the actual exploration can be designed to the emission current pulsewidth corresponding to the target body according to the conductivity, therebyenhancing the effectiveness of the airborne electromagnetic exploration.Finally, design and implement the software platform of electromagnetic dataanalysis in Tau domain. Finish it according to a modular C++and Matlab mixedprogramming, and based on GUI, making electromagnetic data analysis in Taudomain easier to operate. Through the platform of the measured data analysis in Taudomain, the results showed consistent between survey line cross-sectional imagingand decomposition coefficients A, the use of conductive and resistive limits imagingcan reduce the interference of the power line to determine the exact location of theabnormal body.