The Study Of Ground-Motion Prediction Equations In China Using The Hybrid Empirical Method

China is one of the most seismically active regions in the world,so the establishment of prediction equations of strong ground motion parameters applicable to different structural areas in China is of great significance for the work of earthquake protection and disaster reduction.At present,there is a lack of strong earthquake observations in most regions of our country,and the establishment of strong ground motion prediction equation is mainly deduced by the indirect method based on intensity attenuation data,which lacks a clear physical basis.In this paper,the active tectonic area represented by Sichuan-Yunnan region and the stable tectonic area represented by southeast China are selected.Based on the strong earthquake observations and small to medium earthquake data,various seismological methods are used to constrain the effects caused by focal and medium.At last,the prediction models of horizontal strong ground motion which are suitable for different structural regions in our country are established by the hybrid empirical method.The main researches of this paper are as follows:1.Strong ground motion records and moment magnitudes of all events are collected for both Sichuan-Yunnan region and southeast of China.By combining the hypoDD double difference relocating method and genetic algorithm,the location of fault place and distance information are determined by minimizing the distances from the relocated aftershocks to the fault plane.Based on the drilling date,site category information of stations and the modified site estimation model based on elevation gradient,the VS30 of all stations were estimated,and finally the strong earthquake data sets in both SichuanYunnan region and southeast of China were established respectively.2.The inelastic attenuation coefficient of Sichuan-Yunnan region is determined by the empirical method and the random vibration simulation method based on the regional Q value respectively.The geometric attenuation and inelastic attenuation models of the southeast of China are established by using the joint inversion method based on small to moderate seismic records.The stress drops of all earthquakes in the two regions are determined by the method of matching the simulated to observed response spectral shapes over a wide frequency range and the stress parameter models of both regions are established respectively.Through the residual analysis between the source,site and distance terms of the model and the observed data,the model adjustment coefficients of both regions are determined.Finally,the ground motion prediction equations of the two regions are established respectively using the hybrid empirical method.The model can estimate PGA,PGV and 5%damped PSA of the earthquakes for Mw 3.0～9.0 and RRup=0～400 km,and the standard deviation of the model residuals has been calculated quantitatively.3.The comparative analysis results show that the strong ground motion prediction equation established in this paper is in good agreement with the actual observations in Sichuan-Yunnan region,especially the simulation of the attenuation characteristics of strong ground motion parameters with distance is more reliable.The residual difference between the predicted values and the observed values is small,too.But the attenuation rate of the observed data in the far field with distance is obviously slower than the simulation results.The ground motion prediction model for southeast China established in this paper has also well simulated the actual attenuation characteristics of regional strong ground motion parameters with distance.Compared with other prediction models in this region,the error between the predicted value of our model and the observations of strong ground motion parameters in southeast China is the smallest,and the results are the most reliable.However,as the strong ground motion data in southeast of China are very limited,the effectiveness of the new model needs to be further tested.