Inversion Of Geophysical Parameters Using Multi-Agent Genetic Algorithm

Most of geophysical inversion belong to the optimazition of multi-stream cost function.However,conventional inversion methods such as generalized linear inversion and so on are based on linear theory or quasi-linear theory,which results in sensitive to initial model and local extreme and multi-extreme.The conventional methods can hardly meet the requirment for more complex subsurface conditions and sophisticated processing.So an important route to improve the status is to introduce newer and more outstanding ideas and algorithms in geophysical domain.In this paper, we use some new cutting-edge interdisciplinary research to improve on the simple genetic algorithm, developed the multi-agent genetic algorithm for geophysical inversion.Based on analysis of prevailing requests of geophysical inversion and drawbacks of inversion methods today in this paper,the author first introduces multi-agent genetic algorithm in geophysical inversion field which is applied successfully in other optimal fields,considering the global searching and rapid convergence.This algorithm involves several operators,including the initial population,neighborhood competition operator, neighborhood orthogonal crossover operator, mutation operator and self-learning operator.With the standard test functions to test the algorithm, and then,I study the feasibility of the multi-agent genetic algorithm to solve magnetotelluric inversion and seismic impedance inversion, carring out a large number of theoretical model testing, and inversion results are analyzed.Focused on the research of multi-agent genetic algorithm in finding a solution to the geophysical inversion problems,this paper consists of four parts as follow.The first part reviews the study status of inversion problems briefly,and shows the significance,the train of thought,the major content,and the innovation of this project's rearch.The second part gives the review of the proposed non-linear inversion,the development and classification ,the advantages and limitations ,non-linear inversion method.And discussing the characteristics of nonlinear,non-unisequeness,and multi-stream to the gephysical inversion problems.The third part and the fourth part are the main work of this paper.In the third part,the author proposed a realizing scheme for geophysical inversion problems with nonliear and multi-stream properties,based on the fundaments of multi-agent genetic algorithm and the key step of the method,such as eighborhood competition operator, neighborhood orthogonal crossover operator.In the forth part,I use the standard test functions to test the algorithm.And then,appling the algorithm to the MT and seismic acoustic impedance inversion.Results show that multi-agent genetic algorithm is a statable and effective nonliear inversion method with global convergence.Multi-agent genetic algorithm not only has many advantages of some nonlinear optimization algorithm , such as the initial model selected from the restrictions, can easily be integrated with other optimization algorithms (joint or mixed) or parallel computation can be achieved, so that improve the calculation speed.This fully shows the method of practical value.The theoretical model of geophysical data inversion results of forward and efficiency, also shows that multi-agent genetic algorithm for solving geophysical inverse problem of great potential.