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作者:: 罗桂纯¹; 2; 李小军²; 3; 傅磊²; 王玉石²; (1.北京市地震局,北京 100080; 2.中国地震局地球物理研究所,北京 100081; 3.北京工业大学,北京 100124)

Author(s):: LUO Guichun¹; 2; LI Xiaojun²; 3; FU Lei²; Wang Yushi²; (1.Earthquake Administration of Beijing Municipality,Beijing 100080,China)(2.Institute of Geophysics,China Earthquake Administration,Beijing 100081,China)(3.Beijing University of Technology,Beijing 100124,China)

Keywords:: Fourier specturm; velocity response spectrum; HVSR spectral ratio; site effect; predominant frequency; nonlinearity

摘要:: 针对汶川地震近断层的众多量大面广的Ⅱ类场地,选用理县木卡台作为研究对象,采用主震、余震和地脉动记录,基于傅里叶谱HVSR谱比和速度反应谱HVSR谱比结果,研究场地反应的非线性特征。结果表明:主震、余震、地脉动的速度反应谱HVSR谱比曲线平滑,峰值突出,清楚地给出了场地的卓越频率; 场地地震反应随着PGA的变化出现明显的非线性反应,随着PGA的增大,小于100 gal余震、100～200 gal余震、200～300 gal余震以及主震的记录中场地卓越频率有向低频偏移的趋势。

Abstract:: SC Ⅱ stations do have an overall majority near the fault.We select the mainshock,aftershocks,and microtremors strong-motion observation data of the Wenchuan earthquake recorded by the Lixianmuka station.This paper calculates the HVSR spectral ratio of the Fourier amplitude spectrum and velocity response spectrum,and analyzes the nonlinearity of site effect.Research shows the predominant frequency from the HVSR spectral ratio of velocity response spectrum is much more prominent.The result shows that the site response appears obvious nonlinearity when PGA in different scale.The predominant frequency of the site is gradually decreasing along with the PGA of >100 gal aftershocks,100-200 gal aftershocks,200-300 gal aftershocks,and the mainshock.