不同震级下安丘—莒县断裂速度脉冲分布研究

Velocity pulse distributions along the Anqiu-Juxian fault during earthquakes of varying magnitudes

安丘—莒县断裂是沂沭断裂带中时代最新、地震危险性最大的断裂。有限差分法具有差分离散容易、计算效率高的特点。利用有限差分法建立安丘—莒县断裂M_(W)7.0、M_(W)6.5、M_(W)6.0三个震级下的运动学震源模型,模拟不同设定震级下的地震情景。通过脉冲识别方法识别区域内虚拟观测点的模拟结果,得到速度脉冲分布。结果表明:(1)强速度脉冲主要出现在断层在地表的投影区域附近,对于近断层区域的长周期建筑,考虑速度脉冲的影响尤为重要。(2)震级通过影响地震动的幅值影响速度脉冲的分布范围。文章中的长周期地震动需要满足峰值速度大于20 cm/s的条件,才能识别出速度脉冲。(3)脉冲周期的最小值出现在断层与地表的交线附近,震级越大,区域内的脉冲周期越高。研究成果能够有效用于长周期结构的抗震分析,为安丘—莒县断裂附近区域重大工程的建设和地震危险性分析提供参考。

As the latest active fault in the Yishui fault zone,the Anqiu-Juxian fault has the highest seismic risk in the area.The finite difference method can easily separate differences and offers high computation efficiency.In this study,we used the finite difference method to establish the kinematic source model of the Anqiu-Juxian fault during M_(W)7.0,M_(W)6.5,and M_(W)6.0 earthquakes and simulated scenario earthquakes of setting magnitudes.We identified the simulation results at virtual observation points in the study area through pulse identification and then obtained the velocity pulse distributions.The following three results were obtained:(1)Strong velocity pulses appear near the projection area of the fault on the surface,and it is crucial to consider the influence of velocity pulses on near-fault long-period buildings.(2)Magnitude affects the velocity-pulse distribution ranges by influencing the ground-motion amplitude.In this work,velocity pulses can only be identified when the peak velocity of long-period ground motion exceeds 20 cm/s.(3)The minimum value of the pulse period appears near the intersection between the fault and the surface,and the larger the magnitude,the longer the pulse period in the area.These results can be used for the seismic analysis of long-period structures and serve as a valuable reference for the seismic-hazard analysis of construction megaprojects in the vicinity of the Anqiu-Juxian fault.