地震地质 ›› 2019, Vol. 41 ›› Issue (6): 1497-1510.DOI: 10.3969/j.issn.0253-4967.2019.06.012

• 研究论文 • 上一篇    下一篇

汶川地震热异常与构造应力关联的数值模拟

朱传华, 单新建, 张国宏, 焦中虎, 张迎峰, 李彦川, 乔鑫   

  1. 中国地震局地质研究所, 地震动力学国家重点实验室, 北京 100029
  • 收稿日期:2019-04-23 修回日期:2019-07-07 出版日期:2019-12-20 发布日期:2020-03-10
  • 通讯作者: 单新建,男,1966年生,研究员,主要从事地壳形变观测与动力学研究,E-mail:xjshan@163.com
  • 作者简介:朱传华,男,1989年生,2017年于中国石油大学(华东)获地质资源与地质工程专业博士学位,主要从事热流固耦合的数值模拟研究,E-mail:zhu_chuanhua@163.com。
  • 基金资助:
    国家自然科学基金(41631073,41701409)、重大自然灾害监测预警与防范重点研发项目(2018YFC1503602)和中国地震实验场专项(2018CSES0205)共同资助

TWO DIMENSIONAL MODEL ON RELATION BETWEEN THERMAL ANOMALY BEFORE WENCHUAN EARTHQUAKE AND TECTONIC STRESS

ZHU Chuan-hua, SHAN Xin-jian, ZHANG Guo-hong, JIAO Zhong-hu, ZHANG Ying-feng, LI Yan-chuan, QIAO Xin   

  1. State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, China
  • Received:2019-04-23 Revised:2019-07-07 Online:2019-12-20 Published:2020-03-10

摘要: 地震孕育的过程中,在一定时空范围内会出现热异常现象,该异常可能与构造活动存在密切联系,能否利用与构造活动相关的物理过程解释该热异常现象,目前尚未取得共识。为进一步揭示构造应力与地震热异常的关系,文中基于二维多孔介质热流固(THM)耦合模型,模拟了汶川地震前由于断层应力释放引发的热异常演化特征,发现流体对流和岩体应力致热效应导致的热异常现象在空间分布、时间演化、异常量级上皆与观测数据有较好的一致性。结果显示:汶川地震前,受断层应力释放的影响,热异常现象主要出现在断裂带及其相邻的上盘区域,沿断层走向呈带状分布,以增温异常为主,断裂带区域可发生短时降温;断裂带区域热异常受流体对流和应力致热作用联合控制,增温强度先增大后减小,通常可产生高于1K量级的空气增温;非断裂带区域的增温强度主要取决于流体对流作用的强弱,在地震前逐渐增强,对渗透率的响应显著,通常当渗透率≥ 10-13m2时,才能出现1K量级的空气增温异常。文中分析认为,地震前断层应力释放引起的流体热对流浅地表存在蠕滑现象,蠕滑速率为4和应力致热作用可以解释地震前的热异常现象。

关键词: 地震前, 汶川地震, 孔弹性模拟, 应力致热

Abstract: It has been reported that there is thermal anomaly within a certain time and space preceding an earthquake, and previous research has indicated potential associations between the thermal anomaly and earthquake faults, but it is still controversial whether physical processes associated with seismic faults can produce observable heat.Based on rock experiments, some scholars believe that the convective and stress-induced heat associated with fault stress changes may be the cause of those anomalies. Then, did the thermal anomaly before the Wenchuan earthquake induced by the fault stress change?It remains to be tested by numerical simulations on the distribution and intensity of thermal anomalies. For example, is the area of thermal anomaly caused by the fault stress changes before the earthquake the same as the observation?Is the intensity the same?To clarify the above questions, a two-dimensional thermo-hydro-mechanical(THM)finite element model was conducted in this study to simulate the spatial and temporal variations of thermal anomalies caused by the underground fluid convection and rock stress change due to the tectonic stress release on fault before earthquake. Results showed that the simulated thermal anomalies could be consistent with the observed in magnitude and spatio-temporal distribution. Before the Wenchuan earthquake, deformation-related thermal anomalies occurred mainly in the fault zone and its adjacent hanging wall, which are usually abnormal temperature rise, and occasionally abnormal cooling, occurring in the fault zone after the peak temperature rise. In the fault zone, the thermal anomaly is usually greater than the order of 1K of the equivalent air temperature and is controlled by the combined effect of fluid convection and stress change. The temperature increases first and then decreases before the earthquake. In the hanging wall, it's weaker than that of the fault zone, mainly depending on the convection of the fluid. The temperature gradually increases before the earthquake and is dramatically affected by the permeability. Usually, only when the permeability is larger than 10-13m2, can the air temperature rise higher than 1K occur. The results of this study support the view that fluid convection and stress change caused by fault slip before the earthquake can produce observable air temperature anomalies.

Key words: pre-earthquake, Wenchuan earthquake, poroelastic model, stress induced warming

中图分类号: