四川汶川Ms 8.0级地震同震变形特征和分段性
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摘要
汶川地震发育2条地表破裂带,一条沿中龙门山活动断裂带分布,另一条沿前龙门山活动断裂带分布,前者长超过200km,后者长约80km。同震变形在地表表现为逆冲膝折带,走向N45～60°E,形成公路路面隆起和农田陡坎。逆冲膝折带西北侧抬高,东南侧下降。在剖面上冲断带倾向北西,倾角50～60°。膝折带两侧相对高差沿映秀-北川断裂一般为2.5～3.0m,沿都江堰-汉旺断裂为1.5～1.1m。沿中龙门山活动断裂带,同震变形运动方式具有明显的分段性,映秀-擂鼓镇段,表现为逆冲,走滑现象不明显;北川-青川段既有逆冲又有右旋走滑分量。沿前龙门山活动断裂带,同震变形运动方式主要表现为逆冲,走滑位移和分段性不明显。
There are two seismic fractured zones developed when the Wenchuan earthquake happened. One occurred along the ac- tive fault-zone in the central Longmen Mts. and the other in the front of Longmen Mts.. The length of which is more than 200km and about 80km respectively. The co-seismic deformation shows thrust flexural belt with strike of N45°~60°E in the ground, which caused uplift at its northwest side and subsidence. The fault face dips to northwest with dip angle ranged from 50° to 60°. The vertical offset of the flexural belt ranges 2.5-3.0m along Yingxiu-Beichuan seismic fault, and 1.5-1.1m along Dujiangyan-Hanwang fault. Movement of co-seismic deformation presents obvious segmented features along the active fault-zone in the central Longmen Mts., for instance, in the section from Yingxiu to Leigu town, thrust without evident slip occurred; while from Beichuan to Qingchuan, thrust and dextral strike-slip both happened. But main movement along the front Longmen Mts shows thrust without slip and seg- mented features.
There are two seismic fractured zones developed when the Wenchuan earthquake happened. One occurred along the ac- tive fault-zone in the central Longmen Mts. and the other in the front of Longmen Mts.. The length of which is more than 200km and about 80km respectively. The co-seismic deformation shows thrust flexural belt with strike of N45°~60°E in the ground, which caused uplift at its northwest side and subsidence. The fault face dips to northwest with dip angle ranged from 50° to 60°. The vertical offset of the flexural belt ranges 2.5-3.0m along Yingxiu-Beichuan seismic fault, and 1.5-1.1m along Dujiangyan-Hanwang fault. Movement of co-seismic deformation presents obvious segmented features along the active fault-zone in the central Longmen Mts., for instance, in the section from Yingxiu to Leigu town, thrust without evident slip occurred; while from Beichuan to Qingchuan, thrust and dextral strike-slip both happened. But main movement along the front Longmen Mts shows thrust without slip and seg- mented features.
引文
[1]Alexander L Densmore,Michael A Ellis,Yong Li,et al.Active tec-tonics of the Beichuan and Pengguan faults at the eastern margin of the Tibetan Plateau[J].Tectonics,2007,26,TC4005,doi:10,1029/2006TC001987.
[2]杨晓平,蒋溥,宋方敏,等.龙门山断裂带南段错断晚更新世以来地层的证据[J].地震地质,1999,21(4):341-345.
[3]唐荣昌,文德华,黄祖智,等.松潘龙门山地区主要活动断裂带第四纪活动特征[J].中国地震,1991,7(3):64-71.
[2]杨晓平,蒋溥,宋方敏,等.龙门山断裂带南段错断晚更新世以来地层的证据[J].地震地质,1999,21(4):341-345.
[3]唐荣昌,文德华,黄祖智,等.松潘龙门山地区主要活动断裂带第四纪活动特征[J].中国地震,1991,7(3):64-71.
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