Research On The Influence Of Distance Between Stations On Fitting Parameters In Coherency Function Model Of Spatial Variation Of Seismic Ground Motion And Methods For Improvement

Nowadays,the main method for describing spatital variation is the coherency function,scholars from native and abroad put forward a large number of coherency function models,which has two main parameters,one is 1)which means frequency and d which represents distance between stations,among them,distance between stations for spatial variation of seismic ground motions researching generally ranges from tens of meters to several kilometers,the range and number of selection for distance between stations d produces an effect on fitting results.for example,for different distance between stations,fitting parameters can be obtained separately according to hypothetical coherency functions,similarly,unified fitting parameters for coherency coefficient of all distance between stations can also be obtained.while the fitting curve(parameters)of a certain distance between stations and of all distance between stations obtained by unified regression is not march,which with large deviation to some distance between stations.This paper put forwards a method for modificantion in order to reduce the deviation.the main work and achievements for researching is as follows:Firstly,taking acceleration record of four earthquake which of event5,event39,event43,event45,calculating coherency coefficient of 12 different distance between stations d ranged from 200 m to 3000 m,selecting Loh coherency function model,fitting based on calculating results of 12 different distance between stations.It can be found after comparation that the fitting results of a certain distance between stations and of all stations has obvrous deviation which will be larger or smaller while the distance between stations longer or shorter.Secondly,putting forward a method of second regression for parameters of different distance between stations.analyzing MES,RMSE,SEE,R-square of modificantion models and select which given in the paper(which shown in chart4-22).Selecting Loh coherency function model for verificantion study,the results shows that,the compliance of fitting curve calculated from modified parameters with which of certain distance beween stations obvriously improved,the method put forward in this paper can greatly increase the fitting accuracy.the result of fitting parameters modificantion based on Loh coherency function model will be given in the end of paper.