Study On 2D Gravity Gradient Tensor And Seismic Simultaneous Joint Inversion

The gravitational gradient tensor has a higher resolution relative to the gravitational data,and contains multiple components that can provide more abundant source information.Seismic exploration has high longitudinal resolution and good stratification ability.Under the condition of igneous rock and gypsum rock,the quality of seismic data is poor and the identification of abnormal body is difficult.The density and velocity of the igneous rock and the salt rock are obviously different from those of the surrounding rock.According to the joint inversion of the gravity data and the seismic data,the density and velocity of the anomalous body can be distinguished,which can better reflect the underground structure,Abnormal bodyAt present,there are several problems in the simultaneous inversion of the heavy earthquake in China.First,the velocity density relationship,the joint inversion is based on the physical model of the rock.The empirical formula is used to determine the fixed density and velocity relationship,which can not reflect the true situation of underground geological;Second,the joint synchronization of heavy earthquake inversion is inversion of geological interface,few attribute parameters inversion.Based on the above problem,this paper uses the cross gradient function to couple the velocity and density,and restrain it according to the similarity of the structure.The objective function is constructed and the Lagrangian multiplier inversion method is used to carry out the gravitational gradient tensor and seismic joint inversion,Get the speed and density of underground media.Firstly,the grid is divided into rectangular size and the target area is subdivided.Then,the time domain finite difference is used to carry out the seismic forward modeling and the analytic method to carry out gravity gradient tensor forward.Finally,the cross gradient function is chosen as the objective function The objective function and the constraint condition are transformed into a minimum extremum problem of linear equality constraint,and the Lagrangian multiplier is used to solve the problem.The inversion algorithm is tested by the model trial.The results show that the effect of joint inversion is better than that of single inversion.The gravity and seismic data of the Okinawa Trough area are selected,and the combined inversion algorithm is applied to the actual data.Combined with the geological knowledge and logging data,the distribution of the igneous rock is deduced to verify the practicability and effectiveness of the method.