Research And Application Of Edge Detection And Joint Inversion Method With Gravity And Magnetic Data

Gravity and magnetic exploration plays an important role in the interpretation of the distribution,location,attitude and geological implications of geological bodies with different density and magnetic susceptibility in the subsurface.At the same time,gravity and magnetic exploration has become an irreplaceable and important method for geophysical exploration because of its characteristics of low cost,high efficiency,wide coverage,and unconstrained measurement process.In gravity and magnetic surveying,the measured gravity and magnetic data are superimposed anomalies caused by geological bodies with different depths and scales in the subsurface.In order to achieve the division of structures,the location delineation of the anomalous and the extraction of physical characteristics.On the one hand,the edge detection of the gravity and magnetic anomaly data highlights the boundary of each geological body to achieve rapid structural division and delimitation of the anomaly.On the other hand,physical properties and position information of the anomalous underground body are obtained through physical property inversion calculation.In this thesis,the development status of gravity and magnetic data edge detection methods are firstly reviewed in detail.The total horizontal derivative method,vertical derivative method,total gradient modulus method,tilt angle method and Theta map method are analyzed,especially the advantages and disadvantages.Secondly,in order to determine the features of the homogenous target,this thesis also studies the gravity-magnetic joint inversion.Comparing the domestic and overseas research status,the model calculation and analysis of the structural coupling method based on the cross-gradient function are performed.In order to further improve the reliability of joint inversion of gravity and magnetic data,this thesis improves the conventional structure coupling method based on cross-gradient function,and proposes a cross-gradient structure coupling method based on edge detection method.The model test result has a higher vertical resolution than that of smooth separate inversion.Finally,this paper inverts the gravity and magnetic data of the Qiabuqia town in Qinghai Gonghe Basin.There are hot dry rocks with specific gravitational characteristics in Gonghe area,and there are more faults and other structures at the same time.Firstly,the edge detection method is used to analyze and demarcate the regions with homologous.For the two delineated areas,the dry hot rock was delineated by the method proposed in the paper and verified in the known area.The results show that this method can effectively improve the inversion accuracy and has certain practical significance for the development of geothermal geological resources.