台站间距d的分布对地震动空间相干函数的影响

The influence of the distribution of station distance d on the ground motion's coherence function

对地震动空间相干函数进行拟合时,常常遇到台站间距离d偏少的问题。对不同距离台站对的不足对相干函数模型拟合参数的影响进行了对比分析。选取了SMART-1台阵第45号地震的水平分量加速度作为分析数据,计算了d等于200 m,1 000 m和2 000 m等3个台站间距的空间相干系数,并对3个距离的所有计算值进行了拟合,得到了第一组拟合参数;另外又增加计算了d等于400 m,800 m和1 200 m等3个台站间距的空间相干系数,并对所有6个距离的计算值进行了拟合,得到了第二组拟合参数。结果表明,第二组拟合参数的离散性优于第一组拟合参数,且根据第二组拟合参数计算得到的相干系数曲线更合理。因此建议,当采用统计方法获得地震动空间相干函数时,应尽量多地考虑不同距离台站对的强震记录。

When fitting the coherence function of ground motion,we often encounter the problem that the distance d between stations is too litter. This paper mainly studied how the discrepancy of the distance d between stations exerts influence on the fitting parameters of the coherence function model. Taking the No. 45 earthquake’s horizontal component acceleration as the analysis object,the author calculates the value of lagged coherency when d is 200 m,1 000 m,and 2 000 m,all the calculated values of the three distances were fitted and the first set of fitting parameters was obtained. Similarly,the calculated values of all six distances were fitted and the second set of fitting parameters was obtained. The results show that the dispersion of the second set of fitting parameters is superior to the first set of fitting parameters and the coherence coefficient curve calculated based on the second set of fitting parameters is more reasonable. Therefore,when statistical methods are used to obtain coherent functions,the strong motion records at different stations should be considered as much as possible.