鲜水河断裂带关键地段构造应力场数值模拟研究
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摘要
鲜水河断裂带是我国西部最大的走滑断裂带之一,地表形迹上显著的错断水系、错断阶地、断层陡崖、边坡脊及断塞塘等地貌现象和近15mm/a的滑动速率使之成为全国乃至全球近代以来最为活跃的断裂之一。
本文是在收集鲜水河地区已有地质资料的基础上,依据遥感解译和野外调查成果,分别选取乾宁盆地、虾拉沱盆地和康定新城建立平面和三维有限元模型,综合震源机制解和地应力资料反演左旋左阶断裂带的构造应力场特征,探讨乾宁盆地、虾拉沱盆地的形成机理,为该地区构造应力场综合分析提供定量结果,同时为典型地貌构造—拉分盆地区地壳稳定性评价提供依据。取得的认识有：
(1)在乾宁盆地和虾拉沱盆地中部表现为贯通的低应力区,这种在走滑断裂带内的低应力环境,对盆地的形成具有重要的控制作用；次二级断裂左旋右阶形成的岩桥区内,均表现为高应力区,区内岩体遭受挤压,形成推挤构造。
(2)断裂单元两侧应力特征呈四象限分布,两端顺时针方向—侧为挤压区,逆时针方向一侧为张拉区,这种沿断裂面不同地段倾滑性质的变化,对断裂的枢纽运动具有一定的控制作用,地貌上常表现为断裂两盘沉积和剥蚀正、负两个区域。
(3)区内主应力矢量场总体为NE—SW向压应力,在乾宁盆地区转变为NE—SW向的拉应力,印证了左旋左阶羽列断层反扭作用造成的水平拉伸效应,表现为近东西向连接乾宁断裂和雅拉河断裂带的具有张扭性质的中古断裂,与实际构造特征吻合。
(4)构造应力作用下,地势较低的河谷及等高线变化梯度大的区域往往形成高应力区,随着地层深度的增大,主应力的变化受地形起伏的影响逐渐减弱。
Xian Shuihe fault belt is one of the largest fault belts in the west of China, which becomes one of the most active fault zones in the country as well as the whole world, as a result of the significant geomorphic phenomena,such as broken river fault, dislocation terraces, fault, cliff,slope spinal and 1,acting on the surface and the 15mm/a slip rate.
This article is on the basis of the Xian Shuihe region related geological data and interpretation of remote sensing and field survey results, selects the Qianning basin, Xia latuo Basin and Kangding new city to establish planar and three-dimensional finite element model focal mechanism solutions, considers Retrieval of L-left order stress and the tectonic stress of the fault zone besides the formation mechanism of Qianning basin, Xia latuo Basin and finally provides quantitative results of the comprehensive analysis and the stability evaluation of the crust in the typical landscape structures-pull-apart basins. Knowledge acquired is as follows:
(1) The significant low stress area in the low-stress environment of the fault belt in Qianning basin and Xia Latuo basin has an important controlling role in the formation of the basin. When the local rocks are crushed, the rock bridge area in the secondary fault belt characterized by high stress area often forms the pushing construction.
(2) Both sides of fracture unit's stress show a characteristic distribution in four quadrants. The clockwise side is compression zone, and the counterclockwise side is tension zone. The changing of the dip-slip along the different fracture surface sections has a certain control action for the hub of the fault belt. It is usually characterized by two landscapes: deposition and erosion fracture, and positive and negative erosion.
(3) The local principal stress vector field is NE-SW compressive stress, and it changes into NE-SW direction in Qianning Basin, which confirms anti-torsion tension effect due to anti-torsion in Yu-order L-left bar fault. The trans-tensional nature of the Middle fracture east-west connected between the Qianning fault and the Yarra River fault is consistent with the actual structural characteristics.
(4) In the tectonic stress, high stress area tends to be formed in low-lying valley and contour gradients. With the increasing depth of the stratum, the changes impacted by principal stress are gradually weakened.
本文是在收集鲜水河地区已有地质资料的基础上,依据遥感解译和野外调查成果,分别选取乾宁盆地、虾拉沱盆地和康定新城建立平面和三维有限元模型,综合震源机制解和地应力资料反演左旋左阶断裂带的构造应力场特征,探讨乾宁盆地、虾拉沱盆地的形成机理,为该地区构造应力场综合分析提供定量结果,同时为典型地貌构造—拉分盆地区地壳稳定性评价提供依据。取得的认识有：
(1)在乾宁盆地和虾拉沱盆地中部表现为贯通的低应力区,这种在走滑断裂带内的低应力环境,对盆地的形成具有重要的控制作用；次二级断裂左旋右阶形成的岩桥区内,均表现为高应力区,区内岩体遭受挤压,形成推挤构造。
(2)断裂单元两侧应力特征呈四象限分布,两端顺时针方向—侧为挤压区,逆时针方向一侧为张拉区,这种沿断裂面不同地段倾滑性质的变化,对断裂的枢纽运动具有一定的控制作用,地貌上常表现为断裂两盘沉积和剥蚀正、负两个区域。
(3)区内主应力矢量场总体为NE—SW向压应力,在乾宁盆地区转变为NE—SW向的拉应力,印证了左旋左阶羽列断层反扭作用造成的水平拉伸效应,表现为近东西向连接乾宁断裂和雅拉河断裂带的具有张扭性质的中古断裂,与实际构造特征吻合。
(4)构造应力作用下,地势较低的河谷及等高线变化梯度大的区域往往形成高应力区,随着地层深度的增大,主应力的变化受地形起伏的影响逐渐减弱。
Xian Shuihe fault belt is one of the largest fault belts in the west of China, which becomes one of the most active fault zones in the country as well as the whole world, as a result of the significant geomorphic phenomena,such as broken river fault, dislocation terraces, fault, cliff,slope spinal and 1,acting on the surface and the 15mm/a slip rate.
This article is on the basis of the Xian Shuihe region related geological data and interpretation of remote sensing and field survey results, selects the Qianning basin, Xia latuo Basin and Kangding new city to establish planar and three-dimensional finite element model focal mechanism solutions, considers Retrieval of L-left order stress and the tectonic stress of the fault zone besides the formation mechanism of Qianning basin, Xia latuo Basin and finally provides quantitative results of the comprehensive analysis and the stability evaluation of the crust in the typical landscape structures-pull-apart basins. Knowledge acquired is as follows:
(1) The significant low stress area in the low-stress environment of the fault belt in Qianning basin and Xia Latuo basin has an important controlling role in the formation of the basin. When the local rocks are crushed, the rock bridge area in the secondary fault belt characterized by high stress area often forms the pushing construction.
(2) Both sides of fracture unit's stress show a characteristic distribution in four quadrants. The clockwise side is compression zone, and the counterclockwise side is tension zone. The changing of the dip-slip along the different fracture surface sections has a certain control action for the hub of the fault belt. It is usually characterized by two landscapes: deposition and erosion fracture, and positive and negative erosion.
(3) The local principal stress vector field is NE-SW compressive stress, and it changes into NE-SW direction in Qianning Basin, which confirms anti-torsion tension effect due to anti-torsion in Yu-order L-left bar fault. The trans-tensional nature of the Middle fracture east-west connected between the Qianning fault and the Yarra River fault is consistent with the actual structural characteristics.
(4) In the tectonic stress, high stress area tends to be formed in low-lying valley and contour gradients. With the increasing depth of the stratum, the changes impacted by principal stress are gradually weakened.
引文
[1]C.R.艾伦等著.活动构造学[M].成都：四川科学技术出版社,1989.四川省地震局译
[2]马宗晋,李裕彻,朱世龙.近年来我国地震地质工作的进展与展望[J].中国地震,1988,4(2)
[3]郭增建,秦保燕,李孟銮.用震源机制资料讨论中国境内现代的构造运动[M].成都：中国地球物理学会1963年学术讨论会文集,科学出版社
[4]林宝钦.三维构造应力场的平面处理[J].地质科学,1975,(4)
[5]吕戈培,廖华.鲜水河断裂形变场、重力场、磁场动态演化特征与地震[J].四川地震,2011,(3)：11-16
[6]孙竹凤,范天佑.汶川地震主震断层构造应力场数值分析[J].北京理工大学学报,2010,30(3)：253-257
[7]商琳.构造应力场研究进展[J].内江科技,2010,(7)：23-24
[8]李天袑,杜其方等鲜水河断裂带及强震危险性评估[M]成都：成都地图出版社,1998.
[9]钱洪,C.R.艾伦等.全新世以来鲜水河断裂的活动特征[J].中国地震,1988,4(2)：9-17
[10]钱洪.中美联合考察鲜水河断裂概述[J].国际地震动态,1987,(10)：9-10
[11]杨永林,苏琴.鲜水河断裂带现今活动特征研究[J].大地测量与地球动力学,2007,27(6)：22-27
[12]王敏,沈正康等.GPS连续监测鲜水河断裂形变场动态演化[J].中国科学,2008,38(5)：575-581
[13]桂焜长,顾国华.鲜水河断裂带的现今水平形变及构造动态[J].地震地质,1992,14(1)：61-66
[14]唐文清,刘宇平等.鲜水河断裂及两侧地块的GPS监测[J].西南交通大学学报,2005,40(3)：313-317
[15]钱洪.鲜水河断裂反“多”字型地裂缝带的成因机制[J].地震地质,1983,5(3)：9-17
[16]方颖,江在森等.汶川Ms8.0地震前后鲜水河断裂南段的变形特征[J].大地侧量与地球动力学,2010,30(3)：75-79
[17]张东宁,许忠淮.青藏高原现代构造应力状态及构造运动的三维粘弹性数值模[J].中国地震,1994,(4)：136-143
[18]龙德雄,邓天岗.鲜水河断裂带地震活动及其现代构造应力场的有限单元分析[J].地 震研究,1985,8(4)：505-514
[19]白武明,腾春凯,王新华.鲜水河断裂带多断层相互作用流变断裂力学分析[J].地球物理学报,1990,33(3)：308-317
[20]洪汉净,刘辉,郑秀珍.鲜水河断裂带的地震模拟[J].四川地震,2006,(4)：5-10
[21]唐荣昌,韩渭宾.四川活动断裂与地震[M].北京：地震出版社,1993.
[22]唐荣昌,钱洪等.道孚6.9级地震的地质构造背景与发震构造条件分析[J].地震地质,1984,6(2)：33-40
[23]闻学泽等.鲜水河全新世断裂带的分段性、几何特性及其地震构造意义[J].地震学报,1989,11(4)：360-370
[24]董玉善.川西地区地应力测量[J].四川地震,1983,(2).
[25]闻学泽.鲜水河断裂带未来三十年内地震复发的条件概率[J].中国地震,1990,6(2)：8-16
[26]Turcotte D.L and Schubert G.Geodynamics:applications of continuum physics to geological problems[M].John Wiley, New York,1982
[27]Carl Bowin, Scheer E and Smith W.Depth estimates from ratios of gravity, geoid and gradient anomalies[J]. Geophys-ics,1986,51(1):123-136
[28]Allen C.R, Lou Z.L, Qian H,et al. Field study of a highly active fault zone:The Xianshuihe fault of southwestern China [J]. Geol Soc Am Bull.1991,103(9):1178-1199.
[29]Savage J G, Prescott W H.Asthenosphe rjc readjustment and the earthquake cycle[J].J Gephys Res,1978,83:3369-3376
[30]Scholz C H. The Mechanics of Earthquakes and Faulting[J].2nd ed.Cambridge,New York,2002.471.
[31]Duba A G, Hugh Corey, Duba A G. The Brittle—Ductile Transition in Rocks:the Heard volume, Washington, D.C[J]. American Geophysical Union,1990.243
[32]王敏,沈正康,牛之俊等.现今中国大陆地壳运动与活动块体模型[J].中国科学(D辑),2003,33：21-32
[33]刘本培.虾拉沱地震断层蠕动的观测与研究[J].地壳形变与地震,1985,5(4)：357—365
[34]王椿镛,吴建平,楼海等.青藏高原东部壳幔速度结构和地幔变形场的研究[J].地学前缘,2006,13(5)：349-359.
[35]Tse S T, Rice J R. Crustal earthquake instability in relation to the depth variation of frictional slip properties[J]. Geophys. Res,1986,91(B9):9452-9472
[36]Kato N.Seismic cycle on a strike-slip fault with rate-and state-dependent strength in an elastic layer overlying a viscoelastic half-space. [J]. Earth, Planets Space,2002,54(11): 1077-1083
[2]马宗晋,李裕彻,朱世龙.近年来我国地震地质工作的进展与展望[J].中国地震,1988,4(2)
[3]郭增建,秦保燕,李孟銮.用震源机制资料讨论中国境内现代的构造运动[M].成都：中国地球物理学会1963年学术讨论会文集,科学出版社
[4]林宝钦.三维构造应力场的平面处理[J].地质科学,1975,(4)
[5]吕戈培,廖华.鲜水河断裂形变场、重力场、磁场动态演化特征与地震[J].四川地震,2011,(3)：11-16
[6]孙竹凤,范天佑.汶川地震主震断层构造应力场数值分析[J].北京理工大学学报,2010,30(3)：253-257
[7]商琳.构造应力场研究进展[J].内江科技,2010,(7)：23-24
[8]李天袑,杜其方等鲜水河断裂带及强震危险性评估[M]成都：成都地图出版社,1998.
[9]钱洪,C.R.艾伦等.全新世以来鲜水河断裂的活动特征[J].中国地震,1988,4(2)：9-17
[10]钱洪.中美联合考察鲜水河断裂概述[J].国际地震动态,1987,(10)：9-10
[11]杨永林,苏琴.鲜水河断裂带现今活动特征研究[J].大地测量与地球动力学,2007,27(6)：22-27
[12]王敏,沈正康等.GPS连续监测鲜水河断裂形变场动态演化[J].中国科学,2008,38(5)：575-581
[13]桂焜长,顾国华.鲜水河断裂带的现今水平形变及构造动态[J].地震地质,1992,14(1)：61-66
[14]唐文清,刘宇平等.鲜水河断裂及两侧地块的GPS监测[J].西南交通大学学报,2005,40(3)：313-317
[15]钱洪.鲜水河断裂反“多”字型地裂缝带的成因机制[J].地震地质,1983,5(3)：9-17
[16]方颖,江在森等.汶川Ms8.0地震前后鲜水河断裂南段的变形特征[J].大地侧量与地球动力学,2010,30(3)：75-79
[17]张东宁,许忠淮.青藏高原现代构造应力状态及构造运动的三维粘弹性数值模[J].中国地震,1994,(4)：136-143
[18]龙德雄,邓天岗.鲜水河断裂带地震活动及其现代构造应力场的有限单元分析[J].地 震研究,1985,8(4)：505-514
[19]白武明,腾春凯,王新华.鲜水河断裂带多断层相互作用流变断裂力学分析[J].地球物理学报,1990,33(3)：308-317
[20]洪汉净,刘辉,郑秀珍.鲜水河断裂带的地震模拟[J].四川地震,2006,(4)：5-10
[21]唐荣昌,韩渭宾.四川活动断裂与地震[M].北京：地震出版社,1993.
[22]唐荣昌,钱洪等.道孚6.9级地震的地质构造背景与发震构造条件分析[J].地震地质,1984,6(2)：33-40
[23]闻学泽等.鲜水河全新世断裂带的分段性、几何特性及其地震构造意义[J].地震学报,1989,11(4)：360-370
[24]董玉善.川西地区地应力测量[J].四川地震,1983,(2).
[25]闻学泽.鲜水河断裂带未来三十年内地震复发的条件概率[J].中国地震,1990,6(2)：8-16
[26]Turcotte D.L and Schubert G.Geodynamics:applications of continuum physics to geological problems[M].John Wiley, New York,1982
[27]Carl Bowin, Scheer E and Smith W.Depth estimates from ratios of gravity, geoid and gradient anomalies[J]. Geophys-ics,1986,51(1):123-136
[28]Allen C.R, Lou Z.L, Qian H,et al. Field study of a highly active fault zone:The Xianshuihe fault of southwestern China [J]. Geol Soc Am Bull.1991,103(9):1178-1199.
[29]Savage J G, Prescott W H.Asthenosphe rjc readjustment and the earthquake cycle[J].J Gephys Res,1978,83:3369-3376
[30]Scholz C H. The Mechanics of Earthquakes and Faulting[J].2nd ed.Cambridge,New York,2002.471.
[31]Duba A G, Hugh Corey, Duba A G. The Brittle—Ductile Transition in Rocks:the Heard volume, Washington, D.C[J]. American Geophysical Union,1990.243
[32]王敏,沈正康,牛之俊等.现今中国大陆地壳运动与活动块体模型[J].中国科学(D辑),2003,33：21-32
[33]刘本培.虾拉沱地震断层蠕动的观测与研究[J].地壳形变与地震,1985,5(4)：357—365
[34]王椿镛,吴建平,楼海等.青藏高原东部壳幔速度结构和地幔变形场的研究[J].地学前缘,2006,13(5)：349-359.
[35]Tse S T, Rice J R. Crustal earthquake instability in relation to the depth variation of frictional slip properties[J]. Geophys. Res,1986,91(B9):9452-9472
[36]Kato N.Seismic cycle on a strike-slip fault with rate-and state-dependent strength in an elastic layer overlying a viscoelastic half-space. [J]. Earth, Planets Space,2002,54(11): 1077-1083