基于强震动记录确定的场地卓越周期

本文介绍了3种根据场地强震动记录获取场地卓越周期的方法: ① 地表记录的傅里叶谱分析法； ② 地表水平/垂直傅里叶谱比法； ③ 地表/地下傅里叶谱比法. 基于日本强震动观测台网KiK-net中两个基岩台站和两个Ⅲ类场地台站获取的数百条强震动记录， 分别使用上述3种方法确定场地的卓越周期， 并对比分析各种方法的优缺点及其适用情况. 结果表明: 对于基岩场地， 由于记录信息复杂， 局部场地条件对地震动影响较小， 地震动自身特性突出， 导致3种方法所得到的结果均比较分散； 对于土层场地， 场地条件影响比较显著， 3种方法基本都可以得到一个较为准确的数值； 但对于某些场地， 地表水平/垂直傅里叶谱比法所得结果存在不确定性， 相比之下， 地表/地下傅里叶谱比法则能给出一个更为准确的场地卓越周期值. 

Determination of site dominant period based on strong motion records

In this paper, we introduce three methods for determining dominant period based on the strong motion records, they are ① the Fourier spectral analysis method of surface records； ② horizontal/vertical Fourier spectral ratio method； ③ surface/underground Fourier spectral ratio method. Several hundred strong motion records from two bedrock stations and two stations on site class Ⅲ in the KiK-net strong motion observation network in Japan are used to analyze the site dominant period. It is concluded that， on the bedrock site， the dominant frequency obtained from the three methods are scattered due to the hard rock site condition which has little effect on the ground motion. On the soil site， the overlying soil has great effect on the ground motion， and accurate values of dominant period can be obtained from the three methods. The dominant frequency from the surface/underground Fourier spectral ratio method is more accurate than that from the surface horizontal/vertical Fourier spectral ratio method whose result is uncertain on some soil sites.