Simulation of long-period ground motion in the Osaka sedimentary basin: performance estimation and the basin structure effects
Simulation of long-period ground motion in the Osaka sedimentary basin: performance estimation and the basin structure effects
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DOI：
10.1111/j.1365-246x.2010.04556.x
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发表时间：
2010-05
影响因子：
2.8
通讯作者：
A. Iwaki;T. Iwata
中科院分区：
文献类型：
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作者：
A. Iwaki;T. Iwata
基于两种类型的长周期地面运动特征，我们评估了日本西部大阪沉积盆地三维地下速度结构模型在长周期地面运动（3-20 s）模拟中的适用性：(1)特定地震引起的强地面运动；(2)不同方位地震获得的特定地点、与事件无关的水平-垂直频谱比（HV）特征。对于第一种类型，我们在速度波形和伪速度响应谱方面比较了观测到的和合成的地面运动；然后，我们提出了一个客观的指标来评估从一个站点到下一个站点的拟合优度。模拟结果令人满意地再现了许多站点观测到的地面运动；然而，该模型需要改进，以再现一些站点的地面运动。对于第二种类型，我们首先证明了可以从不同方位角的强震观测记录的尾数据部分获得特定地点的HV特征。然后，我们证明了从不同方位角地震的三维地面运动模拟（3DHV）中获得的hv也具有特定地点的稳定值。将合成的3DHV与观测到的HV进行了比较，结果表明，三维盆地速度结构模型能够在±1 s内再现多个站点的HV峰值周期。然而，部分台站的3DHV峰值周期比观测到的HV峰值周期有系统地延长1.5 s以上，这与地面运动模拟拟合优度评分较差的台站相对应。并将3DHV与基本瑞利波的理论椭圆度（1DHV）进行了比较。3DHV和1DHV在某些位点的峰值时段不一致，说明3DHV受位点周围结构横向异质性的影响。我们发现了特定地区3DHV和1DHV峰值差异的系统偏倚特征。影响3DHV的空间范围与基岩构造的复杂程度和3DHV的支配期有关。
SUMMARY We assessed the applicability of the 3-D subsurface velocity structure model of the Osaka sedimentary basin in western Japan for simulations of long-period ground motion (3–20 s) based on two types of long-period ground motion characteristics: (1) strong ground motion from a specific earthquake and (2) site-specific, event-independent horizontal-to-vertical spectral ratio (HV) characteristics obtained from earthquakes with various azimuths. For the first type, we compared the observed and synthetic ground motions in terms of velocity waveforms and pseudo-velocity response spectra; we then proposed an objective index to evaluate the goodness-of-fit from one site to the next. The simulation satisfactorily reproduced the observed ground motion at many stations; however, the model needs improvement for reproducing the ground motion at some stations. For the second type, we first demonstrated that site-specific HV characteristics can be obtained from the coda portion of strong motion observation records for earthquakes with various azimuths. We then demonstrated that the HVs obtained from 3-D ground motion simulations for earthquakes with various azimuths (3DHV) also have sitespecific stable values. The synthetic 3DHV was compared with the observed HV, and the 3-D basin velocity structure model was demonstrated as able to reproduce the HV peak periods within ±1 s at many stations. However, at some stations, the peak periods of the 3DHV were systematically longer than those of the observed HV by more than 1.5 s, which corresponded to the stations of poor goodness-of-fit scores in the ground motion simulation. 3DHV was also compared with the theoretical ellipticity of the fundamental Rayleigh wave (1DHV). The peak periods of 3DHV and 1DHV were inconsistent with each other at some sites, which implies that 3DHV is affected by the lateral heterogeneity of the structure around the site. We found the systematically biased characteristics of the discrepancy in 3DHV and 1DHV peaks in specific regions. The spatial extent of the area that affects 3DHV is related to the complexity in the bedrock structure and the dominant period of 3DHV.