Selection of VS30 Empirical Estimation Model for Sites Consideration of Geological Condition Dependent-A Case of Xinjiang Area
Earthquakes occurs in Xinjiang area frequently with high intensity and serious damage,that calls for seismic hazard analys-is in this area certainly.The site effect is an important factor affecting the result of seismic hazard analysis.Different site conditions give different contributions on site amplification on earthquake ground motions.As we have known,VS30 is one of the important parameters used commonly to characterize site condition.In some cases,however,the drilling depth can not reach 30 m due to limited funds or oth-er reasons so that the true value of VS30 cannot be obtained directly,which traises a popular research issue that how to choose a reason-able VS30 empirical estimation model.In this regard,a total of 1307 engineering boreholes in Xinjiang area have been collected.The boreholes are classified into six types based on their site surface geological age extracted from geological map.For five empirical mod-els used commonly at present,both the correlation coefficient testing and logarithmic distribution testing methods are used to evaluate which model is the most suitable one for each type of geological unit.The results show that the correlation coefficient testing method is ineffective,but the kurtosis and skewness coefficients under the lognormal distribution testing method is capable of selecting the most suitable model for each geological unit.Finally,the VS30 values of all engineering boreholes are calculated with selected empirical mod-els,and the spatial distribution of VS30 values in Xinjiang are obtained by Kriging interpolation,which can provide valuable site informa-tion for potential users of VS30 in this area.The method proposed in this study can also provide the technical base for selection of VS30 empirical estimation models in other regions of China.
Earthquake hazardGeological ageVS30Correlation coefficientLognormal test
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