2021年9月16日四川泸县MS6.0地震强地面运动特征分析

The strong ground motion characteristics of MS6.0 Luxian,Sichuan,earthquake on 16 September 2021

  • 摘要: 2021年9月16日4时33分在四川省泸州市泸县发生MS6.0地震,震中附近的强震动观测台网获取了1 320组三分向加速度记录,对有效记录进行常规处理后计算出地震动相关参数,并利用克里金插值方法得到峰值加速度PGA、峰值速度PGV和拟加速度反应谱的空间分布图。结果显示,极震区与中远场的长轴方向有较大差异,地震动表现出沿断裂走向衰减较慢的特性。通过与常用衰减关系预测值进行对比,分析了PGA和多个周期的拟加速度反应谱随距离的衰减特性,结果显示此次地震的PGA相比衰减关系预测值偏小,拟加速度反应谱相比各经验预测值呈现周期越大衰减变慢的特点,体现出川东南地区特有的衰减规律。最后分析了本次地震获得的最大加速度记录,进一步验证了局部地形和场地对地震动有显著影响。

     

    Abstract: At 04:33 on September 16, 2021, a MS6.0 earthquake occurred in Luxian, Luzhou city, Sichuan Province. Based on the 1 320 sets of three-dimensional acceleration recordings from the strong motion network nearby the epicenter, we calculated the ground motion related parameters after routine processing of the recordings. With the Kriging interpolation method, we obtained the spatial distribution maps of PGA, PGV and pseudo-acceleration response spectrum. The results show that there are great differences in the direction of the major axis between the meizoseismal area and the mid-far field, which reflects the characteristics of slow attenuation along the fault strike. By comparing the calculated data with the commonly used attenuation relationship prediction values, we analyzed the attenuation characteristics of PGA and pseudo-acceleration response spectrum of multiple periods with distance. It shows that the PGA value of this earthquake is generally smaller than the predicted value by the attenuation relationship. And the pseudo-acceleration response spectrum shows that the larger the period, the slower the attenuation by comparing with the empirical predicted values. This reflects the local attenuation characteristics of the southeastern Sichuan. We also analyzed the maximum acceleration record obtained from this earthquake. Finally we verified that the local topography and site have significant impact on ground motion.

     

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