汶川Ms8.0地震前后青藏块体东北缘的垂直形变
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摘要
利用区域水准、跨断裂水准资料,分析了2008年汶川8.0级地震前后青藏块体东北缘地壳垂直形变。结果表明:震前近10年,垂直形变具有明显的区域性和差异化特征。其中,祁连-河西地区垂直形变主要反映祁连山下沉、河西走廊相对抬升的逆继承性运动;西吉、海原、固原地区构造运动相对平稳;兰州、天水、漳县-武都以西的岷山隆起抬升速率明显增大并伴有形变高梯度带。这主要反映了震前青藏高原北向推挤作用相对减弱,东向挤压作用明显增强;震后,2008年8—10月的观测显示,垂直形变出现反向大幅变化;2006—2008年岷山隆起区相对临夏呈现逆继承性的快速下沉,反映由于地震的发生,导致青藏高原东向挤压运动减弱;2010年的监测表明,垂直形变幅度减小,2008—2010年合作相对临夏仍呈现反向下沉,但差异运动明显减弱,显示当前包括岷山隆起在内的区域构造活动已基本趋于稳定。
The vertical crust deformation of northeast margin of Qinghai-Tibet block before and after Wenchuan Ms8.0 earthquake has been analyzed with the regional leveling and fault-crossing leveling data.The results show that within 10 years before the earthquake the regional vertical deformation has a certain diversity with regional feature.In detail,that the tectogenesis for degressive Qilian mountain and anabatic aisle-basin in Hexi area reflected by the vertical deformation is counter-inheritance motion;that the tectogenesis in Xiji-Haiyuan-Guyuan area reflected by the vertical deformation is balanced motion,and on the west to Zhangxian-Wudu of Lanzhou-Tianshui-Wudu area,Minshan's rise is obviously increasing and accompanied with high gradient belt.It could be inferred that the pressure from the Tibetan plateau is relatively weakened in the north direction and clearly increased in the east direction.Monitoring data show that the vertical deformation of northeast margin of Qinghai-Tibet has an extensive inverted variation from Aug.to Oct.in 2008 after Wenchuan Ms8.0 earthquake.The Xiahe and Hezuo area of Minshan uplift shows rapid counter-inheritance sinking relative to Linxia from 2006-2008.It could be inferred that the pressure eastward from the Tibetan plateau is weakened due to Wenchuan Ms8.0 earthquake.The monitoring data in 2010 show that the crustal vertical deformation of northeast margin of Qinghai-Tibet is decresing,and that Hezuo area is counter-inheritance sinking relative to Linxia from 2008-2010,nevertheless,the differential morement between Hezuo and Linxia is decreasing.It could be inferred that regional tectogenesis reflected by the vertical deformation,including Minshan uplift,has been to stable state.
The vertical crust deformation of northeast margin of Qinghai-Tibet block before and after Wenchuan Ms8.0 earthquake has been analyzed with the regional leveling and fault-crossing leveling data.The results show that within 10 years before the earthquake the regional vertical deformation has a certain diversity with regional feature.In detail,that the tectogenesis for degressive Qilian mountain and anabatic aisle-basin in Hexi area reflected by the vertical deformation is counter-inheritance motion;that the tectogenesis in Xiji-Haiyuan-Guyuan area reflected by the vertical deformation is balanced motion,and on the west to Zhangxian-Wudu of Lanzhou-Tianshui-Wudu area,Minshan's rise is obviously increasing and accompanied with high gradient belt.It could be inferred that the pressure from the Tibetan plateau is relatively weakened in the north direction and clearly increased in the east direction.Monitoring data show that the vertical deformation of northeast margin of Qinghai-Tibet has an extensive inverted variation from Aug.to Oct.in 2008 after Wenchuan Ms8.0 earthquake.The Xiahe and Hezuo area of Minshan uplift shows rapid counter-inheritance sinking relative to Linxia from 2006-2008.It could be inferred that the pressure eastward from the Tibetan plateau is weakened due to Wenchuan Ms8.0 earthquake.The monitoring data in 2010 show that the crustal vertical deformation of northeast margin of Qinghai-Tibet is decresing,and that Hezuo area is counter-inheritance sinking relative to Linxia from 2008-2010,nevertheless,the differential morement between Hezuo and Linxia is decreasing.It could be inferred that regional tectogenesis reflected by the vertical deformation,including Minshan uplift,has been to stable state.
引文
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7张四新,等.跨断裂水准剖面观测在地震监测中的应用[J].地震地磁观测与研究,2005,26(4):22-28.(ZhangSixin,et al.The application of leveling survey crossing frac-tures to earthquake monitoring[J].Seismological and Geo-magnetic Observation and Research,2005,26(4):22-28)
8高曙德,等.汶川8.0级地震前后电磁场的变化特征[J].地球物理学报,2010,53(3):512-525.(Gao Shude,etal.The change characteristics of electromagnetic field beforeto after Wenchuan Ms8.0 earthquake[J].Chinese Journal ofGeophysics,2010,53(3):512-525)
2张四新,等.汶川8.0级地震前后地壳垂直形变分析[J],大地测量与地球动力学,2008,(6):43-46.(ZhangSixin,et al.Analysis of crustal vertical deformation beforeand after Wenchuan Ms8.0 earthquake[J].Journal of Ge-odesy and Geodynamics,2008,28(6):43-46)
3张希,等.借助最小二乘配置整体解算地壳视应变场[J].地壳形变与地震,1996,(2):57-62.(Zhangxi,etal.Whole calculation of the crustal visual strain field withthe least square collocation[J].Crustal Deformation andEarthquake,1998,18(2):57-62)
4虢顺民,等.青藏高原东北缘晚第四纪块体划分与运动态势研究[J],地震地质,2000,22(3):219-231.(GuoShunmin,et al.Division and motion status of blocks for thenortheastern Tibetan plateau in late quaternary[J].Seismol-ogy and Geology,2000,22(3):219-231)
5江在森,等.南北地震带和青藏块体东部近期大地形变与地震特征[J].中国地震,1997,13(2):139-150.(JiangZaisen,et al.The characteristic of recent geodetic deforma-tion and earthquake in North-South China Seismic Belt andeast of the Qinghai-Tibet Plate[J].Earthquake Research inChina,1997,13(2):139-150)
6江在森,等.昆仑山口西Ms8.1级地震前区域构造变形背景[J].中国科学(D辑),2003,33(增刊):163-172.(Jiang Zaisen,et al.Regional tectonlic deformation back-ground before Ms8.1 earthquake on the west of Kunlunmountain pass[J].Science in China(Series D),2003,33(B04):163-172)
7张四新,等.跨断裂水准剖面观测在地震监测中的应用[J].地震地磁观测与研究,2005,26(4):22-28.(ZhangSixin,et al.The application of leveling survey crossing frac-tures to earthquake monitoring[J].Seismological and Geo-magnetic Observation and Research,2005,26(4):22-28)
8高曙德,等.汶川8.0级地震前后电磁场的变化特征[J].地球物理学报,2010,53(3):512-525.(Gao Shude,etal.The change characteristics of electromagnetic field beforeto after Wenchuan Ms8.0 earthquake[J].Chinese Journal ofGeophysics,2010,53(3):512-525)
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