| 青藏高原东北缘断层系统的大地震迁移概率及断层滑动速度的分段特征 |
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| 引用本文： | 孙云强,罗纲,尹力,石耀霖.青藏高原东北缘断层系统的大地震迁移概率及断层滑动速度的分段特征[J].地球物理学报,2019,62(5):1663-1679. |
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| 作者姓名： | 孙云强 罗纲 尹力 石耀霖 |
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| 作者单位： | 1. 中国科学院计算地球动力学重点实验室, 中国科学院大学地球与行星科学学院, 北京 100049;2. 武汉大学测绘学院, 武汉 430079 |
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| 基金项目： | 国家自然科学基金（41574085，41590865，U1839027）及中国地震科学实验场专项（2019CSES0112）资助. |
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| 摘 要： | 青藏高原东北缘是青藏高原隆升、生长及变形前缘.区域地震活动频繁,且地震在其主要断层带之间时空迁移.为了研究区域大地震在主要断层带之间的迁移规律与概率,以及主要断层带大地震破裂的时空分布特征,本文建立了青藏高原东北缘地区的三维黏弹塑性有限元模型,模拟了区域断层系统的地震循环,得到了人工合成的万年时间尺度的地震目录.根据模拟的地震目录,并结合古地震数据,计算分析了大地震(MW≥7)在研究区各个主要断层带之间的迁移概率,探讨了黏度、高程、统计时间长度等因素对大地震在各主要断层带之间的迁移概率和大地震在各主要断层带上的发生概率的影响,并且初步调查了海原断层带和香山天景山断层带的大地震破裂时空分布特征.研究结果显示:继区域最近两次大地震(1920年海原断层带上的M8.5海原大地震和1927年香山天景山断层带上的M8古浪大地震)之后,下一次大地震(MW≥7)发生在海原断层上的概率最大,约为51%～81%;其次是在香山天景山断层上,概率约为9%～37%.模型结果显示,不同的青藏高原中下地壳上地幔黏度大小,对大地震在各个断层带之间的迁移规律和迁移概率的影响较小;而研究区的高程载荷对地震迁移则有显著的影响:高程载荷易于使得海原断层地震活动减弱及香山天景山断层的地震活动增强.研究结果也显示了青藏高原东北缘地区主要断层带的地震活动与断层滑动速率分布的分段性显著;大地震在断层带上的破裂位置并不固定,呈现不均匀性;并暗示了断层几何形状对地震活动、断层滑动速率分布与大地震破裂位置的控制作用.
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| 关 键 词： | 青藏高原东北缘 黏弹塑性有限元模型 地震循环 地震迁移 海原断层 香山天景山断层 |
| 收稿时间： | 2018-03-26 |
Migration probability of big earthquakes and segmentation of slip rates on the fault system in northeastern Tibetan Plateau |
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| SUN YunQiang,LUO Gang,YIN Li,SHI YaoLin.Migration probability of big earthquakes and segmentation of slip rates on the fault system in northeastern Tibetan Plateau[J].Chinese Journal of Geophysics,2019,62(5):1663-1679. |
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| Authors: | SUN YunQiang LUO Gang YIN Li SHI YaoLin |
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| Institution: | 1. Key Laboratory of Computational Geodynamics of Chinese Academy of Sciences, College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China;2. School of Geodesy and Geomatics, Wuhan University, Wuhan 430079, China |
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| Abstract: | The northeastern Tibetan Plateau is the leading edge of uplift, growth and deformation of Tibetan Plateau. Earthquakes occur frequently here, showing the spatio-temporal migration between major fault zones. In order to study such migration and the spatio-temporal distribution of rupture zones caused by big earthquakes, we build a three-dimensional visco-elasto-plastic finite-element model to simulate earthquake cycles and seismicity (synthetic seismic catalog) in northeastern Tibetan Plateau. Based on the model results and paleoseismic data, we analyze migration of big earthquakes (MW ≥ 7) on the major faults in this region, and investigate the effects of different viscosity values of mid-lower crust/upper mantle and topographic loading on earthquake migration and seismic activities on the Haiyuan and Xiangshan-Tianjingshan faults. The model results show that following the 1920 M8.5 Haiyuan earthquake and the 1927 M8.0 Gulang earthquake, the next big event (MW ≥ 7) in northeastern Tibetan Plateau would be most likely to occur on the Haiyuan fault (51%~81%), and secondly, Xiangshan-Tianjingshan fault (9%~37%). We find that the viscosity of the mid-lower crust/upper mantle in northeastern Tibetan Plateau has little effect on the patterns of earthquake migration, but the topographic loading has a significant impact on regional earthquake migration. We also find that earthquakes are characterized by obvious segmentation on major faults in northeastern Tibetan Plateau, and the ruptured zones by big earthquakes are uneven on every fault. The model results also indicate the important effects of fault geometries on seismic activity, fault slip and seismic rupture zones. |
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| Keywords: | Northeastern Tibetan Plateau Visco-elasto-plastic finite-element model Earthquake cycle Earthquake migration Haiyuan fault Xiangshan-Tianjingshan fault |
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