基于实测记录分析场地因素对海底地震动特性影响

At present, the analysis based on the measured records on the seabed has found that there are obvious differences in the ground motion characteristics between the seabed and the land, but it is difficult to further determine the influencing factors of the seabed ground motion characteristics. On the basis of previous studies, compare the differences in the ground motion characteristics between adjacent seabed stations in the same earthquake and analyze the reasons for the differences. Taking the records of 8 strong earthquakes monitored by 6 seabed strong motion stations in the K - NET seismic network in Japan and their adjacent land stations with different site conditions as the research objects, by analyzing the peak acceleration of the strong earthquake records, the horizontal amplification factor spectrum, the ratio spectrum of the vertical and horizontal response spectra, etc., compare and analyze the characteristics of the ground motion of different seabed stations and the differences in the ground motion characteristics between the seabed stations and the adjacent land stations with different site conditions. The research findings are: (1) There are obvious differences in the vertical ground motion between the seabed and the land; (2) There are also relatively large differences and obvious regularities in the ground motion characteristics between different seabed stations, and the site factors such as the seabed site conditions and topography have a relatively large impact on the seabed ground motion characteristics; (3) The characteristic period of the seabed horizontal ground motion response spectrum is relatively large, and the spectral characteristics are between those of the medium - hard soil and soft soil sites on the land.

目前基于海底实测记录的分析发现海底与陆地地震动特性存在明显差异,但难以进一步确定海底地震动特性的影响因素。在以往研究的基础上对比同次地震中相邻海底台站间地震动特性的差异,并分析造成差异的原因。以日本K-NET地震台网中6个海底强震台站及其相邻不同场地条件陆地台站监测的8次强震记录为研究对象,通过分析强震记录的峰值加速度、水平放大系数谱、竖向与水平反应谱的比谱等,对比分析不同海底台站地震动的特性,以及海底台站与相邻不同场地条件陆地台站地震动特性的差别。研究发现:(1)海底与陆地竖向地震动存在明显差异;(2)不同海底台站间地震动特性亦存在较大差异和明显的规律性,海底场地条件、地形等场地因素对海底地震动特性的影响较大;(3)海底水平向地震动反应谱的特征周期较大,谱特性介于陆地中硬土与软土场地间。