逆断层地震作用下三维沉积盆地地震动谱元法模拟

巴振宁; 赵靖轩; 吴孟桃; 梁建文; 塔拉

doi:10.3969/j.issn.2096-7780.2020.10.002

逆断层地震作用下三维沉积盆地地震动谱元法模拟

doi: 10.3969/j.issn.2096-7780.2020.10.002

巴振宁^{1, 2, ,},
赵靖轩¹,
吴孟桃^{1, 2},
梁建文^{1, 2},
塔拉³

1.
天津大学土木系，天津 300354
2.
滨海土木工程结构与安全教育部重点实验室，天津 300350
3.
中国地震局第一监测中心，天津 300171

基金项目: 国家自然科学基金项目（51778413）资助。

详细信息

通讯作者:
巴振宁（1980-），男，教授，主要从事大尺度复杂场地地震动模拟研究。E-mail：bazhenning_001@163.com

中图分类号: P315.9
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- 文章访问数: 400
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出版历程
- 收稿日期: 2020-09-04
- 修回日期: 2020-09-14
- 网络出版日期: 2020-11-09
- 刊出日期: 2020-11-09

Spectral element method simulation of three-dimensional sedimentary basin under reverse-fault earthquakes

Zhenning Ba^{1, 2
, ,},
Jingxuan Zhao¹,
Mengtao Wu^{1, 2},
Jianwen Liang^{1, 2},
La Ta³

1.
Department of Civil Engineering，Tianjin University，Tianjin 300354，China
2.
Key Laboratory of Coast Civil Structure Safety of the Ministry of Education，Tianjin 300350，China
3.
The First Monitoring and Application Center，China Earthquake Administration，Tianjin 300171，China

摘要

摘要: 近断层地震动对近场区域会造成严重的地震灾害，尤其区域内存在沉积地形时会进一步加重灾害。目前，针对释放能量更大、破坏力更强的逆冲断层地震作用下沉积盆地的地震动响应研究还未见报道。本文即采用谱元法，研究了动力学逆断层地震作用下的三维沉积盆地的动力响应。文中以椭球形沉积盆地为例，对其逆断层地震动响应特性进行了分析，并探讨了改变内外介质波速比和沉积厚度时沉积盆地内部观测点地震动时程和峰值变化规律。研究表明：①沉积内外介质波速比对沉积盆地的地震动影响显著，当沉积内部介质波速比降低时，盆地内部地表的峰值响应增大，地震动持续时间明显延长，尤其是位于盆地中心加速度峰值放大2.08倍，持时延长1.97倍；②沉积盆地厚度同样对其地震动响应产生影响，当沉积厚度增加时盆地中心位置地震动响应减小，加速度峰值缩小约0.64倍，而盆地边缘区域的地震动响应明显增大，峰值放大约1.35倍。
- 谱元法 /
- 动力学逆断层 /
- 三维沉积盆地 /
- 近断层地震动
Abstract: Near-fault ground motion can cause serious earthquake disaster in the near-field area, especially when there is sedimentary topography in the area. At present, there are no reports on the ground motion response of sedimentary basins under the action of thrust faults which release more energy and have more destructive force. In this paper, spectral element method is used to establish the overall physical model of the dynamic source containing the reverse fault and the three-dimensional sedimentary basin. The dynamic response of the three-dimensional sedimentary basin under the dynamic reverse fault seismic action is studied. Taking an ellipsoid sedimentary basin as an example, this paper analyzes the characteristics of the ground motion response of its reverse faults, and discusses the time-history and peak variation of the ground motion at the observation points in the sedimentary basin under different wave velocity ratios and thickness of the sedimentary medium. The results show that: ① The wave velocity ratio of medium inside and outside the sedimentary basin has a significant influence on ground motion in the sedimentary basin. When the wave velocity ratio of medium inside the sedimentary basin decreases, the peak response on the surface inside the basin increases, and the duration of ground motion significantly extends. In particular, the peak acceleration in the center of the basin magnifies by 2.08 times, and the duration extends by 1.97 times; ② The thickness of a sedimentary basin also has an impact on its ground motion response. When the sedimentary thickness increases, the ground motion response at the center of the basin decreases by 0.64 times, while the ground motion response at the edge of the basin increases significantly, by about 1.35 times.
- spectral element method /
- dynamic inverse fault /
- three-dimensional sedimentary basin /
- near-fault ground motion

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图 1 沉积盆地整体物理模型

Figure 1. Overall physical model of sedimentary basin

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图 2 整体模型网格划分示意图

Figure 2. Overall model grid division diagram

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图 3 模型内部剖面网格划分示意图

Figure 3. Section grid diagram inside the model

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图 4 断层面上成核区位置及大小

Figure 4. The location and size of the core area on fault surface

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图 5 动力学逆断层作用下各个观测点对应加速度时程曲线

Figure 5. The time-histories of acceleration corresponding to observation point under the action of dynamic inverse fault

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图 6 三维速度波场快照图

Figure 6. Snapshots of the three-dimensional velocity wave field

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图 7 不同沉积内外介质波速比下，地表观测点加速度时程曲线

Figure 7. The time-histories of acceleration at surface observation points under different wave velocity ratios of basin medium

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图 8 不同沉积厚度下，地表观测点加速度时程曲线

Figure 8. The time-histories of acceleration at surface observation points under different basin thicknesses

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表 1 计算模型介质参数

Table 1. Properties of the simulation model

介质密度ρ/（kg•m⁻³）		剪切波速v_S/（m•s⁻¹）		压缩波速v_P/（m•s⁻¹）		品质因子Q		深度/km	厚度/km
基岩	沉积盆地	基岩	沉积盆地	基岩	沉积盆地	基岩	沉积盆地	深度/km	厚度/km
2600	2 000	2 000	500	3600	900	600	30	3	3
2600		2 000		3600		600		3	6
3000		3200		5000		900		24	30

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表 2 观测点位置

Table 2. Location of observation point

坐标名称	坐标位置（x，y，z）
P1	（0，2 km，30 km）
P2（盆地边缘）	（0，0 km，30 km）
P3（盆地1/4处）	（0，−3 km，30 km）
P4 (盆地中心)	（0，−6 km，30 km）
P5（盆地1/4处）	（0，−9 km，30 km）
P6（盆地边缘）	（0，−12 km，30 km）

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表 3 断层上的摩擦和应力参数

Table 3. Friction and stress parameters on the fault

断层参数	断层面上核心区	断层面上除核心区以外的部分
粘聚力C，（MPa）	0.2	0.2
静摩擦系数，μ_s	0.6	0.6
动摩擦因数，μ_d	0.2	0.2
滑移弱化距离，δ₀ （m）	0.5	0.5
初始法向应力，σ₀ （MPa）	−0.0026667×h_d	−0.0026667×h_d
初始切向应力，τ₀ （MPa）	C＋σ₀（0.0057＋μ_s）	0.55σ₀
注：表3中h_d为沿断层面倾向的距离

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