给定观测精度下的点(线)源模型重力与磁力垂向识别能力研究

Research on the vertical recognition ability of gravity and magnetic data of point(line)source model with given survey accuracy

重、磁勘探具有效率高、成本低、工作范围广等优点,已在地球物理勘探中得到了广泛应用.前人大多在不考虑重、磁勘探观测精度的条件下进行了垂向识别能力的研究,但在考虑重、磁观测精度条件下,重力(重力异常、重力张量)与磁力(磁力异常、磁力三分量、磁力张量)对孤立异常的垂向识别能力如何则需要进行深入的理论研究.本文从重、磁场正演理论出发,以球体(点源模型)和无限延伸水平圆柱体(线源模型)为例,考虑给定观测精度条件下,以重力和磁力幅值大小与观测精度的关系来研究垂向识别能力,从而消除了背景场的影响,提高了研究结果的可靠度.通过研究表明,对于孤立异常,重力张量在浅部一定深度内比重力异常的垂向识别能力强,该深度与重力异常和重力张量观测精度的比值成正比;垂直磁化磁力张量在浅部一定深度内比化极磁力异常的垂向识别能力强,该深度与磁力异常与磁力张量观测精度的比值成正比;磁力在浅部一定深度内比重力的垂向识别能力强,该深度与地质体的磁化强度和剩余密度比值、重力观测精度和磁力观测精度比值成正比.通过重力和磁力垂向识别能力的研究将为重、磁勘探的实际应用起到指导作用.

Gravity and magnetic exploration have been widely used in geophysical exploration because of the advantages of high efficiency,low cost and wide working range.Most researches on the vertical recognition ability of gravity and magnetic data were considered without survey accuracy.Hence,theoretical research on gravity anomalies,magnetic anomalies and tensor vertical detection ability of isolated anomaly are still necessary with the given gravity and magnetic survey accuracy.The research on vertical recognition ability is based on forward theory of the gravity and magnetic field to study the relationship between amplitude and survey accuracy with given survey accuracy to eliminate the influence of the background field,which improves the reliability of the research results.The study shows that for isolated anomalies,the gravity tensor has a stronger vertical recognition ability than gravity anomalies at a certain shallow depth.This depth is proportional to the ratio of the gravity anomaly survey accuracy to the gravity tensor survey accuracy.The vertical magnetization magnetic tensor has a stronger vertical recognition ability than the polar magnetic anomalies at a certain shallow depth.This depth is proportional to the ratio of the polar magnetic anomalies survey accuracy to the vertical magnetization magnetic tensor survey accuracy.The magnetic field has a stronger vertical recognition ability than gravity at a certain shallow depth.This depth is proportional to the ratio of magnetization to residual density,gravity survey accuracy to magnetic survey accuracy.This result will guide the practical application of gravity and magnetic exploration.