基于强震记录的大阪盆地S波和次生波放大效应研究

Study on the amplification effect of S wave and basin induced wave of Osaka basin based on strong motion records

文中基于大阪盆地强震记录,分离S波和盆地次生波,采用传统谱比法和最小二乘法统计分析二者的放大与盆地深度的关系。研究表明:(1)大阪盆地S波放大和盆地深度在短周期部分(0.1~0.5 s)相关性较强,长周期部分(1.0~3.0 s)则基本不相关;盆地次生波在短周期和长周期均表现很强的深度相关性;(2)在短周期部分,大阪盆地内S波的放大明显大于次生波的放大,在长周期部分,次生波的放大随着盆地深度增加逐渐接近S波放大,当盆地深度大于1200 m,次生波的放大高于S波的放大。(3)不同位置震源引起的盆地内S波和次生波放大差异较为明显。盆地外浅源地震引起的长周期次生波放大与深度相关性很弱,盆地下方地震、盆地外深源地震以及远震引起的长周期次生波则与深度相关性较强。

In this paper,based on the strong motion records in Osaka basin,the S wave and basin induced wave are separated,and the relationships between amplification factor and basin depth of the S wave and basin induced wave are analyzed by using the traditional spectral ratio method and the least square method.The results show that:(1)The S wave amplification in the Osaka basin shows a high correlation with the basin depth in the short period(0.1-0.5 s),but little correlation in the long period(1-3 s).However,the basin induced wave shows strong correlation both in short and long period.(2)The amplification of S wave in short period is obviously larger than basin induced wave.In long period,the amplification of basin induced wave gradually approaches that of S wave with the increase of basin depth.As the basin depth greater than 1200 m,the amplification of basin induced wave is larger than that of S wave.(3)The amplifications of S wave and basin induced wave caused by seismic sources at different locations are significantly different.The amplification of long period basin induced wave caused by shallow earthquakes outside the basin is weakly correlated with the basin depth,whereas that caused by earthquakes below the basin,deep earthquakes outside the basin and distant earthquakes are significantly correlated with it.