Application Of Genetic Algorithm In Inversion Of Focal Mechanism

The focal mechanism solution is one of the nonlinear problems often encountered in seismology.There are many inversion calculation methods related to it.As a newly developed stochastic nonlinear global search algorithm,genetic algorithm is widely used in various geophysical problems.Genetic algorithm is an evolutionary algorithm that simulates biological evolution,species selection,and population genetics.By selecting crossover mutations,the population will be steadily developed in the best direction to achieve survival of the fittest and survival of the fittest.The paper first uses the classical energy ratio method and the AIC algorithm to pick the first pick of the field acquisition data,and obtains the complete P wave arrival data.Then,the crustal velocity structure model was established.[Adjusting the sequence of establishing the velocity structure model and rapid absolute positioning] Using the fast absolute positioning method,the approximate position of the earthquake source was obtained,and the position of the earthquake source was determined using double-difference fine positioning.Finally,the genetic algorithm was used to invert the focal mechanism solution,and the focal mechanism solutions “beach diagram” and “double-couple map” were obtained to obtain focal mechanism parameters.The table of the two focal planes is used to create the table with the orientation,inclination,sliding angle,and the azimuth and inclination of the N axis,P axis,and T axis to represent the focal mechanism parameters.The research area of this paper is the Changning Shale Gas Development Demonstration Zone in the Sichuan Basin,which is located on the southern edge of the Sichuan Basin and has rich mineral resources.In recent years,this area belongs to the national key area for exploration and development of shale gas.The article relies on the scientific research project “Research on the correlation between shale gas development and earthquake induced in the shale gas field of Changning shale gas field” of the Southwest Oil & Gas Field Branch of CNPC.It collects seismic data through field seismic monitoring equipment,analyzes regional seismic events,and uses genetic algorithms to study and obtain The focal mechanism solution and source parameters of the microseism in the study area.