【作者】 刘剑；

【导师】 席振铢；

【作者基本信息】 中南大学 ， 地球探测与信息技术， 2009， 硕士

【摘要】 论文根据瞬变电磁法三分量研究和应用状况,提出了研究三分量响应的意义。论文主要研究了大定源和中心回线装置下薄板导体的三分量响应规律,组合薄板导体的三分量响应规律,导电覆盖层下薄板导体的三分量响应规律以及地形对三分量响应的影响。论文从频率域电磁场各分量表达式出发,推导出时间域均匀半空间表面上垂直磁偶极子源及水平电偶极子源瞬变场的三分量表达式。利用本征电流等效方法模拟计算了薄板导体的三分量响应,组合薄板导体的三分量响应,导电覆盖层下薄板导体的三分量响应以及不同地形条件下薄板的三分量响应。通过模拟计算结果表明,利用X分量可以大致确定板状体的中心,Y分量可以判断板的倾向,Z分量有利于发现异常,也能判断板的倾向,但不如Y分量对倾向反应敏感。对不同装置条件下组合导电板状体的三分量响应,中心回线装置的横向分辨能力要优于大定源装置;对于大定源装置,当P/h＜3时,三分量响应曲线与单个板时的响应曲线形态相似,当P/h≥3时,三个分量的曲线都出现了“双峰”;对于中心回线装置,P/h＜2时难以分辨出组合板,P/h≥2时则能够分辨出组合板。论文通过模拟计算,得出了即使覆盖层与目标体的纵向电导相等（即S₂/S₁=1）时,中心回线装置下X分量和Y分量对目标体也有反映,但在大定源装置条件下三分量响应均没有异常的结论。但是,当S₂/S₁≥5时,三分量响应特征都能清晰地反映目标体。关于地形对三分量响应的影响,模拟计算结果表明,山脊和山谷地形主要影响三分量响应的幅度,对曲线形态影响不大,而山坡地形对三分量响应影响较大,响应特征复杂。此外,垂直分量相对水平分量受地形影响较小,大定源装置相对中心回线装置受地形影响较小。更多还原

【Abstract】 With the study of the TEM response of three-component, this paper proposed the importance of its application in Geophysical prospecting. This paper mainly studied the TEM response of three-component in four conditions: （1） the response for plate in two commonly used configurations, central loop configuration and large fixed source loop configuration; （2）the response for multi-plates model; （3） the response for plates target with conductor overburden on its top;（4） the response for plates with topography.According to the field expressions of all the electromagnetic components in frequency domain, it derives the mathematical expression of the three-component response on the surface in homogeneous half-space in time domain, for both the vertical magnetic dipole source transient field and the horizontal electronic dipole field. The eigencurrent equivalent simulation principle is introduced to calculate the TEM response of three-component for the various models.Results show that: （1）the X-component response roughly determines the projection position of the plate’s center on the ground, the Y-component response reflects the dip direction which does better than The Z-component response, while the Z-component response obviously imply the anomaly. （2） For multi-plates model in the two configurations, the central loop configuration has higher resolution than the large fixed source loop configuration in detecting transverse multi-model. For the latter, when P/h<3, the response curve is similar as the single plate model, when P/h>3, all the three response curves demonstrated double peaks; while for the former, when P/h>2 the multi-model can be prospected. （3）when the ratio factors of the longitudinal conductance between the target （S₂） and the overburden （S₁）equals （S₂/S₁ ）, the X-component and the Y-component response reflect the target under the central loop configuration, while under the large fixed source loop configuration there is no reflection. When S₂ /S₁≥5 , the reflection is obvious. （4） The topography influence on the response of three-component is that: hill and valley terrain mainly affects the response amplitude, with little influence on the response curve shape. However, for step topography, the response amplitude and shape will be changed significantly, it becomes more complex. The vertical component is less affected by terrain than the horizontal component, and large fixed source loop configuration is less affected by terrain than central loop configuration.更多还原