基于山东省场地的沂沭断裂带地震动高频消减作用

High frequency reduction effect of ground motion in Yi-Shu fault zone based on sites of Shandong

摘要:

郯庐断裂带是中国东部一条地震活动频繁的断裂带,发生过多次4.0级以上的地震,沂沭断裂带位于郯庐断裂带中段,曾发生过震级大于6.0级的地震.为了解场地条件对沂沭断裂带地震动的影响,探讨缺乏地震数据区域的地震动估计方法,以沂沭断裂带的地震动波形数据为基础,通过对数据傅里叶谱分析,研究了山东省内场地对沂沭断裂带地震动的高频消减作用,获得了场地高频消减参数Kappa,分析了Kappa与场地平均剪切波速V_S30之间的关系,探讨了Kappa对PGA及反应谱（S_a）等地震动参数的影响.研究表明:作为一种表征场地条件的参数,Kappa具有区域性差异,且随着相应的V_S30的增大而减小；震级相同时,Kappa只对PGA及反应谱的数值大小产生影响,而不影响二者随距离的衰减趋势.本文所得的高频消减参数可以为研究山东省场地对沂沭断裂带地震所受场地效应及模拟该断裂带地震动并分析其特点提供参考.

Abstract:

Located in the east of China, Tancheng-Lujiang fault zone is a region with frequent seismic events. Earthquakes above 4.0 occur multiple times there, most of which concentrate in its middle and northern segments. Yi-Shu fault zone is located in the middle of Tancheng-Lujiang fault zone, where earthquakes above 6.0 have occurred. To study the influence of sites on the ground motion of the Yi-Shu fault zone and explore groud motion estimating method for regions lack of seismic data, the ground motion wave form of Yi-Shu fault zone is analyzed by Fourier spectrum, and the high frequency reduction effect of sites in Shandong on Yi-Shu fault zone ground motion is studied. The high frequency reduction parameter Kappa is obtained, whose relationship with the site average shear wave velocity V_S30 is subsequently discussed. Kappa’s influence on seismic parameters such as PGA and response spectrum S_a is also investigated. Results show that as a parameter characterizing site conditions, Kappa exhibits regional differences, which decrease with the increase of corresponding V_S30. Under the same earthquake magnitude, Kappa only affects the numerical value of PGA and response spectrum, while their respective decay trends remained unaffected. The high frequency reduction parameter Kappa attains in this study can provide reference for research on the site effect in Shandong for earthquakes of Yi-Shu fault zone, as well as the simulation of the Yi-Shu fault zone ground motion and the analysis of its characteristics.