最强脉冲方向分量的周期特性及其影响因素分析

以NGA-West2强震数据库中的243组脉冲型地震记录为数据基础,按照我国场地分类标准对其进行分类,探讨场地条件、断层类型及断层距等对最强脉冲方向分量脉冲周期(T_P)随震级(M_W)变化规律的影响。结果表明:(1)最强脉冲方向分量与垂直断层走向分量的T_P具有强线性相关性,场地条件对二者周期相关性的影响不大;(2)场地土层的剪切波速越大,T_P随M_W增大的速率越快;(3)Ⅲ类场地的T_P值大于Ⅰ,Ⅱ类场地;(4)最强脉冲方向分量T_P随M_W的增大速率要快于垂直或平行断层走向分量;(5)在Ⅰ,Ⅱ类场地条件下,非走滑断层的T_P随M_W的增大速率快于走滑断层,这一规律在Ⅲ类场地条件下正好相反;(6)3类场地非近断层区域的T_P随M_W的增大速率快于近断层区域。建议在使用脉冲周期与震级关系的统计模型时应考虑场地条件、断层类型、断层距及不同国家场地分类标准差异性的影响。

Analysis on the Period Characteristics of the Strongest Pulse Direction Component and Its Influence Factors

Based on the 243 sets of pulse-like seismic records in the NGA-West2 strong earthquake database,we classified the selected seismic records according to the site classification standards of China,and discussed the influences of site conditions,fault types and fault distance on the variation of pulse period T_Pin the strongest pulse direction with magnitudeM_W.The results show that:(1)The T_Pin the strongest pulse direction has a strong linear correlation with the T_Pin vertical fault strike direction,and the site conditions have little effect on the correlation between the two component pulse periods.(2)The greater the shear wave velocity of foundation ground,the faster the T_Pincreases with the increasing of M_W.(3)The predicted value of the pulse period of the class III site is greater than that of the class I site and class II site.(4)T_Pof the strongest pulse direction component increases faster with the increasing of M_Wthan that of the vertical or parallel fault strike component.(5)Under the conditions of class I and II sites,the T_Pof non-strike-slip faults increases with the increasing of magnitude faster than that of strike-slip faults.This rule is exactly the opposite under the conditions of class III site.(6)The T_Pof class I,II and III sites in non-near-fault area increases with the increasing of M_Wfaster than that in near-fault area.It is recommended that we should consider the effects of site conditions,fault types,fault distance and differences of site classification standards in different countries when using a statistical model of the relationship between pulse period and magnitude.