袁明明,李小军,王玉石. 2024. 基于KiK-net强震动记录的加速度反应谱规律性偏差. 地震学报,46(5):1−16. DOI: 10.11939/jass.20230010
引用本文: 袁明明,李小军,王玉石. 2024. 基于KiK-net强震动记录的加速度反应谱规律性偏差. 地震学报,46(5):1−16. DOI: 10.11939/jass.20230010
Yuan M M,Li X J,Wang Y S. 2024. Regular deviations of spectral accelerations based on strong-motion records from KiK-net. Acta Seismologica Sinica46(5):1−16. DOI: 10.11939/jass.20230010
Citation: Yuan M M,Li X J,Wang Y S. 2024. Regular deviations of spectral accelerations based on strong-motion records from KiK-net. Acta Seismologica Sinica46(5):1−16. DOI: 10.11939/jass.20230010

基于KiK-net强震动记录的加速度反应谱规律性偏差

Regular deviations of spectral accelerations based on strong-motion records from KiK-net

  • 摘要: 地震动特性受到地震震源、地震波传播介质和局部场地条件等因素的综合影响,地震动反应谱虽然具有统计意义上的共性特征,但其具体形状又各不相同,特别是部分加速度反应谱与统计平均值间存在显著的规律性偏差。本文基于日本KiK-net台网获取的8万余条强震动记录,建立了考虑地震震级和震中距影响的地面峰值加速度归一化加速度反应谱,并以预测值+0.5倍方差为界将加速度反应谱分为有、无反应谱规律性偏差的两组。通过有反应谱规律性偏差的反应谱(观测值)与无反应谱规律性偏差的反应谱预测值之间的差值,析出了反应谱的规律性偏差,验证了反应谱规律性偏差形状与高斯曲线高度吻合,并可用加速度反应谱规律性偏差的中心周期、相对高度和相对宽度等参数进行表征。基于2万余条有反应谱规律性偏差记录的统计分析显示,加速度反应谱规律性偏差主要受控于剪切波速、覆盖层厚度等局部场地条件表征参数,受地震震级、震中距 \mathrm、 地震动强度等参数的影响相对较小。利用多元线性回归建立了加速度反应谱规律性偏差表征参数的经验统计关系,并提出了有加速度反应谱规律性偏差的场地相关加速度反应谱确定方法。虽有待改进,但本文提出的反应谱规律性偏差概念将有助于改进场地相关地震动反应谱的确定方法,以期为工程抗震设计提供更加合理的场地相关地震动输入。

     

    Abstract:
    The main factors that affect ground motion include the earthquake source, the medium and path of seismic wave propagation and the local site condition. Although the spectral accelerations of ground motion have common characteristics in statistical sense, the specific shape of each acceleration record is unique, and some spectral accelerations have significant regular deviations from the statistical mean values. These deviations often appear in the form of a single-peak superimposed on the average spectral accelerations, which might be related to the earthquake parameters, such as earthquake magnitudes and epicenter distances, and the site parameters, such as shear wave velocity and overburden thickness, and strong motion intensity.
    In this paper, based on the statistical analyses of 85 976 sets of horizontal acceleration records obtained by Japanese KiK-net network, the statistical relationship of the PGA (peak ground acceleration) normalized spectral accelerations with magnitude and epicenter distance was obtained. Using +0.5 time of variances as the separatrix, the acceleration records were divided into two categories, that is, the records with or without egular deviations of spectral accelerations. By calculating the differences between the spectral accelerations of records with regular deviations and the predicted spectral accelerations without regular deviations, the regular deviations of the spectral accelerations were separated out, and the shapes of the regular deviations were verified to be highly consistent with the Gaussian curve. The regular deviations of spectral accelerations could be characterized by the central period, the relative height and the relative width of the fitted Gaussian curves.
    Based on the statistical analyses of 25 229 acceleration records with regular deviations of spectral accelerations obtained by Japanese KiK-net network, the correlations between the characteristic parameters of regular deviations and earthquake parameters, local site conditions, and ground motion intensity were discussed. The results indicated that:
    1) The central periods of regular deviations in logarithmic coordinates were slightly increased with earthquake magnitudes in linear coordinates, slightly increased with epicenter distances in logarithmic coordinates, significantly increased with overburden thickness with shear wave velocity up to 1 km/s, and significantly decreased with 30 m average shear wave velocity vS30, while their trend with strong motion intensity (i.e. PGA) was not obvious. It could be concluded that the central periods of regular deviations were mainly controlled by the local site conditions, and also affected by earthquake magnitudes and epicenter distances.
    2) The relative heights of regular deviations in logarithmic coordinates significantly increased with vS30, and slightly increased with overburden thickness with shear wave velocity up to 1 km/s, while their trend with earthquake magnitudes, epicenter distances or PGA was not obvious. It could be concluded that the relative heights of regular deviations were mainly determined by the local site conditions, while the influences of earthquake magnitudes, epicenter distances, and strong motion intensity were not significant.
    3) The relative widths of regular deviations in logarithmic coordinates significantly increased with vS30, and decreased with earthquake magnitudes, epicenter distances, and overburden thickness with shear wave velocity up to 1 km/s, while the influences of strong motion intensity were not significant. It could be concluded that the relative widths of regular deviations were mainly influenced by the local site conditions and earthquake parameters.
    Selecting average shear wave velocity, cover layer thickness, earthquake magnitude, and epicenter distance as independent variables, empirical statistical relationships to predict the parameters of the regular deviations of spectral accelerations, including the central period, the relative height and the relative width, were given by the multiple linear regression method, which could lead to the following prediction procedure of spectral accelerations considering regular deviations:
    1) Considering the influence of earthquake magnitudes, epicenter distances and local site conditions, determine the site related spectral accelerations without regular deviations by the attenuation relationships (ground motion prediction equations) for spectral acceleration.
    2) Considering the influence of average shear wave velocity, cover layer thickness, earthquake magnitude, and epicenter distance, determine the central period, the relative height and the relative width of regular deviations by the empirical statistical relationships given in this paper.
    3) Determine the regular deviation curve of spectral accelerations by the Gaussian function using independent variables including the central period, the relative height and the relative width.
    4) Superimpose the regular deviation curves of spectral accelerations on the site-related spectral accelerations without regular deviations, and then obtain the site-related spectral accelerations with regular deviations.
    The comparison between the observed spectral accelerations and their predicted values of typical acceleration records with regular deviations showed that the proposed procedure gave a more accurate prediction of spectral accelerations, which could reflect the unique single-peak regular deviations from the statistical mean values of spectral accelerations. Even though, further research was needed on how to determine the criteria for discriminating the strong motion records with/without regular deviations of spectral accelerations based on the parameters of earthquakes, local site conditions and strong motion field.

     

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