基于广义反演法的不同位置地震引起盆地放大效应的研究——以仙台盆地为例

Basin amplification effect caused by earthquakes at different locations based on the generalized inversion method: a case study of Sendai Basin

摘要:

基于强震观测记录,采用广义反演法和HVSR法分析日本仙台盆地48个强震台站以及场地v_S30和盆地深度对放大效应的影响。研究表明,相比于广义反演法,HVSR法能够较好地给出场地主频,但会明显低估放大效应的幅值；处于盆地外不同位置的浅源地震引起的盆地放大效应差异明显,仙台盆地南部海域地震引起的放大效应最大,盆地北部陆地地震引起的放大效应最小;盆地南部和东部地震引起的S波的放大效应与v_S30的相关性较强,北部地震的放大效应与v_S30基本不相关;盆地S波的放大效应与盆地深度在0.5~5 Hz频段内的相关性较强,在0.25~0.5 Hz和5~10 Hz频段内基本不相关。

Abstract:

Based on the strong motion records, the amplification effects of 48 stations in Sendai Basin, Japan, were analyzed by using the generalized inversion and HVSR methods. Then, the impacts of site v_S30 and basin depth on the amplification effect were analyzed. Results show that compared with the generalized inversion method, the HVSR method can provide the main frequency of a site, but it underestimates the amplitude of the amplification effect. The amplification effects of the basin induced by shallow earthquakes in different locations outside the basin considerably vary. The amplification effect caused by ocean earthquakes in the southern part of Sendai Basin is the largest, whereas that caused by land earthquakes in the northern part of Sendai Basin is the smallest. The amplification effect of S-wave caused by earthquakes in the southern and eastern parts of the basin shows a strong correlation with v_S30, whereas that in the northern part shows little correlation with v_S30. The amplification effect of the S-wave in the basin is strongly correlated with the depth of the basin in the frequency band of 0.5-5 Hz but is basically irrelevant in the frequency band of 0.25-0.5 and 5-10 Hz.