汶川地震前后龙门山地区区域构造应力场演化的数值模拟
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摘要
以龙门山地区为研究对象,采用数值模拟方法,通过模拟强震发生前后以及发生时的构造应力场特征,得到了龙门山地区构造应力场变化规律。结果表明,龙门山地区在汶川地震到地震时到地震后的最大主应力和剪应力的数值和方向均发生了改变,最大主应力方向整体上由NEE变为SEE,但在不同地区这种变化表现有所差异。剪应力在震前和震时均有局部区域出现了集中,特别是在映秀附近;但在地震后,区域内剪应力相对均匀分布,而且与地震前相比,剪应力在龙门山前山断裂和龙门山中央断裂分布的值明显减小,在后山断裂附近分布的剪应力数值增大。同时地震后剪应力在龙门山中央断裂上集中的区域逐渐向东北方向移动。应力场变化规律与地震时的地表形变规律和震后余震的分布规律一致。
This paper examines the tectonic stress field in the Longmenshan region where the Wenchuan 8.0 earthquake occurred in 2008.The evolution of tectonic stress field before-,during-and after-earthquake is studied with numerical modelling.It is found that from the time before main shock to the time after main shock,the regional stress field experienced complex change process.The magnitudes and orientations of principal stresses and shear stresses changed a great deal.The changes coincide well with the deformation caused by the earthquake and the distribution of the after-shocks.
This paper examines the tectonic stress field in the Longmenshan region where the Wenchuan 8.0 earthquake occurred in 2008.The evolution of tectonic stress field before-,during-and after-earthquake is studied with numerical modelling.It is found that from the time before main shock to the time after main shock,the regional stress field experienced complex change process.The magnitudes and orientations of principal stresses and shear stresses changed a great deal.The changes coincide well with the deformation caused by the earthquake and the distribution of the after-shocks.
引文
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[2]陈国光,计凤桔,周荣军,等.龙门山断裂带晚第四纪活动性分段的初步研究[J].地震地质,2007,29(3):657～673.Chen Guoguang,Ji Fengju,Zhou Rongjun,et al.Primary researchof activity segmentation of Longmenshan fault zone since late-Qua-ternary.Seismology and Geology,2007,29(3):657～673.
[3]邓起东,陈社发,赵小麟.龙门山及其邻区的构造和地震活动及动力学[J].地震地质,1994,26(2):389～403.Deng Qidong,Chen Shefa,Zhao Xiaolin.Tectonics,seismicityand dynamics of Longmenshan Mountains and its adjacent regions.Seismology and Geology,1994,26(2)389～403.
[4]蒋靖祥,尹光华,许凤柱.昆仑山口西8.1级地震前库尔勒测区相对应力场变化[J].地震,2003,23(3):89～96.Jiang Jingxiang,Yin Guanghua,Xu Fengzhu.Relative stress fieldchange of Kuerle region before 8.1 earthquake in western KunlunPass.Earthquake,2003,23(3):89～96.
[5]李勇,周荣军,Densmore AL,等.青藏高原东缘大陆动力学过程与地质响应[M].北京:地质出版社,2006,1～134.Li Yong,Zhou Rongjun,Densmore A.L,et al.The Eastern Mar-gin of Continental Dynamics Process and Geological Response.Beijing:Geological Publishing House,2006,1～134.
[6]龙海英,高国英,聂晓红.1997～1998年伽师强震群震源区应力场特征[J].西北地震学报,2007,29(2):145～149.Long Haiying,Gao Guoying,Nie Xiaohong.Characteristics ofstress field in the focal region of Jiashi strong earthquake swarmfrom 1997 to 1998.Northwestern Seismological Journal,2007,29(2):145～149.
[7]唐荣昌,韩渭宾.四川活动断裂与地震[M].北京:地震出版社,1993.Tang Rongchang,Han Weibing(Eds).Active Faults and Earth-quakes in Sichuan Province.Beijing:Seismological Press,1993.
[8]屠泓为,万秀红,高歌,等.1977～2006年新疆伽师地震断层性质及应力场变化原因初探[J].地球物理学进展,2008,23(4):1038～1044.Tu Hongwei,Wan Xiuhong,Gao Ge,et al.Research of the reasonfor variations of the earthquake fault characters and the stress fieldin the Jiashi region of Xingjing from 1977 to 2006.Progress in Ge-ophysics,2008,23(4):1038～1044.
[9]王凯英,马瑾,顾国华.1996年川滇地区发生的一次应力转向事件[J].地学前缘,2003,10(特刊):233～239.Wang Kaiying,Ma Jin,Gu Guohua.Rotation of stress axis in Si-chuan-Yunnan region in 1996.Earth Science Frontiers,2003,10:233～239.
[10]王勤彩,陈章立,郑斯华.汶川大地震余震序列震源机制的空间分段特征[J].科学通报,2008,53(16):2348～2354.Wang Qincai,Chen Zhangli,Zheng Sihua.Wenchuanearthquake aftershock sequence focal mechanism of space seg-mentation.Chinese science bulletin,2008,53(16):2348～2354.
[11]谢富仁,陈群策,崔效锋,等.中国大陆地壳应力环境研究[M].北京:地质出版社,2003.Xie Furen,Chen Qunce,Cui Xiaofeng,et al.Research of Main-land China Crustal Stress Environment.Beijing:Geological Pub-lishing House,2003.
[12]殷跃平,潘桂棠、刘宇平,等.汶川地震地质与滑坡灾害概论[M].北京:地质出版社,2009.Yin Yueping,Pan Guitang,Liu Yuping,et al.Geology andLandslide Disaster of the Wenchuan Earthquake.Beijing:Geo-logical Publishing House,2009.
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