多辐射场源地空瞬变电磁法多分量全域视电阻率定义

本文针对多辐射场源地空瞬变电磁法理论,建立了相应的多分量全域视电阻率定义方法.分析了利用磁场强度进行多辐射场源地空系统全域视电阻率定义的优点,针对磁场强度的各个分量,提出了各自的全域视电阻率算法,实现了多分量、全时域、全空域视电阻率计算,并分析了偏移距对全域视电阻率的影响.通过调整源的相对位置及电流方向等参数,多辐射源瞬变电磁地空系统不仅可以加强不同分量信号强度,削弱随机干扰,还可更好地分辨地下异常体的位置.通过对所设计模型的处理,证实了多辐射场源地空系统多分量全域视电阻率算法的有效性,也验证了多辐射场源地空系统的优势.

Multi-component full field apparent resistivity definition of multi-source ground-airborne transient electromagnetic method with galvanic sources

Multi-source ground-airborne transient electromagnetic method with galvanic sources has such advantages as strengthening signal intensity, weakening random disturbance, better identifying the position of geological abnormity, etc. However, so far its interpretation method has not been established yet, which restricts the development of this method. This paper chooses the most widely used interpretation parameter-apparent resistivity in our research and builds up multi-component full field apparent resistivity algorithm for multi-source ground-airborne transient electromagnetic method with galvanic sources, which provides an effective and practical interpretation tool for this method.This paper analyzes the advantages of magnetic field intensity in multi-source ground-airborne transient electromagnetic interpretation and puts forward multi-source and multi-component full field apparent resistivity algorithm for each component on the basis of inverse function theorem and iterative method. The results of theoretical models show that the first and last part of the apparent resistivity curve can reach the resistivity of the first and the last layer, respectively. Thus, multi-component, full time and full space apparent resistivity definition is achieved.The results of layered models show that:(1)Full field apparent resistivity can tell the underground electric change smoothly, completely and gradually.(2)When the resistivity of layered model changes, the differentiation of full field apparent resistivity is obvious, which can easily and intuitively identify electric layer.(3)With the change of offset, the difference among apparent resistivity curves of each component is small and they all reflect subsurface structure well.(4)As receiver altitude, offset and time are considered simultaneously in our calculation, full field apparent resistivity can achieve full space and full time apparent resistivity calculation. The results of three dimensional model with a low-resistivity anomaly show that:(1)By changing spatial location and current direction of the galvanic sources, signal intensity of different components can be strengthened or weakened.(2)Full field apparent resistivity sections of each component can all match well with the designed complex model.This paper focuses on multi-component full field apparent resistivity calculation of multi-source ground-airborne transient electromagnetic method with galvanic sources. Full field apparent resistivity algorithm, which is based on inverse function theorem and iterative method, realizes multi-component, full time and full space apparent resistivity calculation and can completely, smoothly and gradually tell the subsurface electrical variations. By changing the spatial location and current direction of galvanic sources, the results of three dimensional model confirm that multi-source ground-airborne transient electromagnetic method with galvanic sources surely can strengthen signal intensity and improve signal-to-noise ratio. Besides, the effectiveness of multi-component full field apparent resistivity algorithm with magnetic field intensity for multi-source ground-airborne transient electromagnetic method with galvanic sources is also verified.