Simulating the near-field pulse-like ground motions of the Imperial Valley, California, earthquake
Simulating the near-field pulse-like ground motions of the Imperial Valley, California, earthquake
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模拟加利福尼亚州因皮里尔谷地震的近场脉冲状地面运动
DOI：
10.1016/j.soildyn.2020.106347
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发表时间：
2020-11-01
影响因子：
4
通讯作者：
Chen, Xueliang
中科院分区：
文献类型：
--
作者：
Luo, Quanbo;Dai, Feng;Chen, Xueliang
近场长周期脉冲型地震动可能会引起大型结构在自振频率处的共振，从而导致结构的严重破坏。为了研究震源大速度脉冲的来源和特征，本研究从位于Imperial Valley M-w 6.5地震近场的32个强震仪中识别出14个具有速度脉冲的台站。采用四阶精度的有限差分法，通过运动学方法模拟了脉冲状地震动。结果表明，断层面北方部分的滑动粗糙体比起源于震源区的粗糙体对大速度脉冲的贡献更大。断层正向分量的双侧脉冲和断层平行分量的单侧脉冲分别主要受断层破裂方向和断层滑动方向的控制。与拟速度反应谱相比，位移反应谱能更好地反映长周期脉冲型地震动对大型结构的共振效应。最大地震动的位置与大粗糙面的地表投影区域相吻合，各水平分量的振幅和衰减率随距断层距离的增加而变化。断层两侧地震动峰值的差异表明，断层正向分量比平行分量对断层倾角更为敏感。通过对模拟的速度时程、反应谱和地震动与实测数据的拟合，再现了1 Hz以下的脉冲状地震动。利用1994年美国帝王谷地震、1994年北岭M-w 6.7地震和1999年集集M-w 7.6地震的脉冲记录，比较了地震震级对速度大脉冲峰值和分布的影响，结果表明，大脉冲峰值和分布具有较好的一致性。近场脉冲型地震动的模拟结果有助于阐明脉冲型地震动的机制。
Long-period pulse-like ground motions in the near-field are likely to induce severe damage to large structures due to resonance at the natural frequencies of engineered construction. To investigate the origin and characteristics of large velocity pulses from the seismic source, this study identifies 14 stations with velocity pulses from 32 strong-motion seismographs located in the near-field of the Imperial Valley M-w 6.5 earthquake. The pulse-like ground motions are simulated by a kinematic approach using a fourth-order accurate finite-difference method. The results show that the slip asperity in the northern part of the fault plane contributes more to large velocity pulses than the asperity that originates in the hypocentral zone. The two-sided pulses on the fault-normal component and the one-sided pulses on the fault-parallel component are mainly regulated by the fault rupture and slip directions, respectively. Compared with the pseudo-velocity response spectrum, the displacement response spectrum better captures the resonance effect of long-period pulse-like ground motion on large structures. The location of the maximum ground motion coincides with the surface projection area of the large asperity, and the amplitude and the attenuation rate of each horizontal component vary with increasing distance from the fault. The difference in the ground motion peaks on both sides of the fault implies that the fault-normal component is more sensitive to the fault dip angle than the fault-parallel component. We reproduce the pulse-like ground motions up to 1 Hz by fitting the simulated velocity time histories, response spectrum and ground motions to observed data. Using the pulse records of the Imperial Valley earthquake, the 1994 Northridge M-w 6.7 earthquake, and the 1999 Chi-Chi M-w 7.6 earthquake, we compare the effects of earthquake magnitude on peak value and distribution of large velocity pulses, in which a reasonable consistency can be observed. Our simulated results of near-field pulse-like ground motions are beneficial to clarify the pulse mechanism.