Presenting a model of earthquake wave velocity changes (V_(P_n )) based on genetic algorithm(Case study - Iran)

Earthquake is one of the most dangerous natural disasters of the present age, which has always shown its importance objectively. An earthquake is a natural disaster that, depending on its magnitude, can cause massive catastrophes in a short time. The purpose of this paper is to extract and present a model for earthquake wave velocity changes (V_(P_n )) using Genetic Algorithm(GA). The data used in this study were received from the National Seismological Center of the Institute of Geophysics, University of Tehran. In this study, three provinces of Kermanshah, East Azerbaijan and Kerman were selected. Earthquake event characteristics of each of these three provinces in the period between 2006 to the end of 2018 and with a focal depth of up to 30 km and magnitude between 4 to 8 were selected.In order to use the Genetic Algorithm(GA), first the data received from the National Seismological Center for these three provinces were merged, which was estimated at 1863 earthquake events. After extracting the relevant data, the earthquake wave velocity (V_(P_n )) was calculated. Then, ignoring about 25% of this data, a mathematical model for earthquake velocity was extracted. Finally, the obtained formula was applied to the initial ignored data (25%), which had similar results. To model the changes in wave velocity according to distance changes, a mathematical relation was considered as an exponential function and the unknown parameters of the model were determined using a Genetic Algorithm(GA). To find a suitable model between distance and speed, the following relation is considered for it.V(x)=a+be^(-kx)In this regard, a, b and k are constant coefficients and x is the distance from the earthquake site in terms of one thousand kilometers. In the above equation, the coefficients must be determined so that the output of this model with the recorded data has the least amount of error. For this purpose, the Genetic Algorithm(GA) optimization method is used. For this purpose, the error between the model output and the actual data was considered as the objective function of the optimization problem and the optimization variables were determined with the aim of minimizing this objective function.The output of the model for training and test data showed that the proposed model has acceptable accuracy for modeling the velocity of longitudinal waves. This model can be used to determine the arrival time of waves of an earthquake to different points. It is also possible to estimate the location of the earthquake by recording the occurrence of the earthquake at several different points and using the provided relationship. In this paper, the average speed of propagation of longitudinal waves of the earthquake in terms of distance from the location of the earthquake was investigated. For this purpose, three different earthquakes in three different parts of Iran are considered And the time of arrival of these waves and their recording in different stations were extracted from the information of the Institute of Geophysics, University of Tehran And having the distance of stations and the difference of wave transmission time, the average speed of the waves was calculated. The same general behavior was observed in all cases and that is to increase the speed of earthquake waves by propagating and traveling at a distance of 7.74 km / s for all three test cases. To model changes in wave velocity in terms of distance changes, A mathematical relation is considered as an exponential function and unknown parameters of the model were determined using genetic algorithm.