土耳其地震强震区近地表剪切波速对地震地面运动的影响及对我国设计谱特征参数修订的启示

    Influence of near-surface shear wave velocity on seismic ground motion in Turkey Earthquake and the enlightenment on revision of seismic design response spectrum characteristic parameters in China

    • 摘要: 2023年2 月6 日土耳其Mw7.8级强烈地震为典型的浅源走滑型地震,造成大规模地表破裂,近断层区域出现超预期的强烈地震动,导致大量房屋倒塌。基于土耳其地震断裂两侧60 km范围内的强地震动记录,系统开展近断层强地震动峰值、频谱、持时的空间分布特征研究,深入剖析场地表层30 m范围内平均剪切波速(VS30)对强地震动特性的影响规律,全面开展近断层实际地震反应谱与我国抗震设计反应谱的对比分析,重点探讨强地震动反应谱特征参数与我国规范设计取值的差异。结果表明:1)土耳其地震近断层区域以Ⅰ1类和Ⅱ类场地为主,峰值加速度大于0.40 g以及放大系数超过3的强烈地面运动主要分布在距离断裂30 km范围内,且普遍为脉冲型地震动;2)峰值加速度放大系数随VS30衰减的拟合结果与经验关系非常接近,而能量持时随VS30的变化规律不明显;3)反应谱特征周期均随VS30的增大而减小,动力放大系数随VS30的增大而增大,80%的反应谱特征周期及45%的动力放大系数均超过我国规范取值;4)类似此次土耳其地震若发生在我国9度设防地区,Ⅰ1类场地-设计地震分组为第一组在周期0.38~1.90 s、Ⅱ类场地-设计地震分组为第一组的设计谱在周期0.65~2.00 s,均未能满足抗震设防的需要。宜适当提高设计反应谱平台高度和增加平台段宽度以适应高烈度地震作用。

       

      Abstract: The February 6, 2023, Mw7.8 Turkey strong earthquake was a typical strike slip shallow source earthquake, caused large-scale surface ruptures. Unexpected strong ground motions caused a large number of buildings collapsed in the near-fault area. Based on strong motion records on both sides within 60 km from Kahramanmaras-Antakya fault, spatial distribution characteristics of peak value, frequency spectrum and duration time of strong ground motions were systematically researched, and the influence law of the average shear-wave velocity of the upper 30 m soil layers (VS30) on strong ground motion were discussed. By comparing actual response spectrums of near-fault records with Chinese design response spectrums, the differences between characteristic parameters were analyzed. The results show that: 1) The near-fault areas of the Turkey earthquake are predominantly composed of Site Class I1 and Site Class II. The strongest ground motions with peak ground accelerations (PGA) more than 0.40 g and amplification factors exceeds 3 are concentrated in a 30 km region of hanging wall and generally belong to pulse-type. 2) The fitting results of PGA amplification factor with VS30 are close to the empirical relationship, whereas the variation rules of energy durations with VS30 is not significant. 3) The characteristic period of response spectrum decreases with the increase of VS30. The amplification factor of response spectrum increases with the increase of VS30. There are 80% characteristic periods and 45% amplification factors of actual response spectrums are larger than the values specified in Chinese codes. 4) If this earthquake occurs in Chinese earthquake fortification intensity IX area, design response spectrum of site-class I1 and design earthquake-1st group during 0.38~1.90 s, as well as site-class Ⅱ and design earthquake-1st group during 0.65~2.00 s, will totally fail to meet the requirements for seismic fortification. This study suggests that the height and the width of design spectrum platform should be raised to fit high intensity ground motion.

       

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