垂直和倾斜断层围陷波的谱元法数值模拟及其波场特征对比

摘要/Abstract

摘要： 低速断层破碎带内传播的断层围陷波是断层内部信息的重要载体,研究其波场特征是反,演断层内部结构的关键。前人对围陷波的模拟主要针对垂直断层,但实际断层大部分是倾斜的。本文利用谱元法数值模拟地震波在垂直和倾斜断层区域的传播,并分别单独改变断层破碎带或断层两盘速度差异等参数,对比分析地震动在时域和频域发生的变化,研究这些参数对波场特征的影响。对比研究表明,当存在一定宽度的低速破碎带时,倾斜断层对近断层区域波场的影响和垂直断层相比在幅值分布上有比较显著的差异,尤其是当断层两盘同时还存在速度差异时;在倾斜和垂直断层破碎带上方,均能产生断层围陷波,其幅值特征差异不大,但在跨断层平面上的质点极化方式可能会存在差异:垂直断层围陷波质点极化方向表现为单一,而倾斜断层可能会出现多个方向。这些模拟结果有助于反演真实断层破碎带结构,也能够加深对近断层的强地面运动特征的认识。

关键词: 断层围陷波, 波场特征, 谱元法数值模拟, 倾斜断层

Abstract: Fault zone trapped waves (FZT Ws) mainly travel along the low velocity cracked fault zone (FZ) and contain significant information about its internal structure, so their wave field characteristics are very important for FZ structure inversion. Previous resear-ches mostly simulated the FZTWs on the vertical fault structures and would bias from the real FZ that were normally inclined. In this paper, we implemented simulations on selected models with a vertical or inclined FZ and compared their wave fields in both time and fre-quency domains. The results show that wave field on the surface has significant different amplitude distribution across both sides of the vertical and inclined faults when low velocity fault zone exist and especially when the two fault walls have velocity contrasts. In addi-tion, the results also indicate that the trapped waves can be created above the FZ for both the vertical and inclined fault with similar amplitude characteristics. However, their polar izations on the cross fault plane would be variant. The polarities trend to be single direc tion for vertical fault but fork to multiple directions for inclined fault. The simulation re-sults can help to invert real FZ structures, and also enhance the knowledge on near fault strong ground motions. .

Key words: Fault zone trapped waves, Spectral element method, Inclined fault, Wave field characteristics

中图分类号:

P315.7

徐洪伟, 王伟君. 垂直和倾斜断层围陷波的谱元法数值模拟及其波场特征对比[J]. 地震, 2014, 34(3): 27-39.

XU Hong-wei, WANG Wei-jun. Simulation and Wave Field Comparison of V ertical and Inclined Fault Trapped Waves by Spectral Element Method[J]. EARTHQUAKE, 2014, 34(3): 27-39.

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