摘要
前人研究1985年8月23日乌恰M_(S)7.4地震在卡兹克阿尔特断层上破裂了15 km,本次研究确定该地震在乌恰盆地南缘断层上也破裂了24 km,最终确定本次地震总破裂长度为39 km。实测乌恰盆地南缘断层地表破裂带最大垂直位移量为1.2 m,最小垂直位移量仅0.2 m,平均垂直位移量0.55~0.64 m,这些断层陡坎只是在地表呈现轻微的隆起,肉眼通常难以识别,因此也是震后未能及时发现的重要原因。探槽开挖揭露该逆冲断层倾向南,倾角仅为20°,计算平均水平缩短位移量为1.51~1.76 m,平均倾滑位移量为1.61~1.87 m,与卡兹克阿尔特断层地表破裂带运动性质相同、断错位移量相当。在最大主压应力南北方向投影显示,两条破裂带基本不重合,即本次大地震的极震区西部的应变能量是由乌恰盆地南缘断层破裂释放,东部的应变能量则由卡兹克阿尔特断层破裂释放,隐含着乌恰盆地南缘断层和卡兹克阿尔特断层之间构造关系密切。这两条断层深部很可能归并为同一条软弱的膏盐滑脱面,均属于帕米尔俯冲带的薄皮构造。
Previous studies performed detailed surveying that Wuqia M_(S)7.4 earthquake on August 23th,1985 ruptured 15 km on Kazikalte fault.In this paper we determine that it also ruptured 24 km on Wuqia Basin South fault,thus this event ruptured the full 39km long.The maximum vertical offset of Wuqia Basin South fault surface rupture zone is 1.2 m,the minimum vertical offset is only 0.2 m,and the average vertical offset is 0.55~0.64 m.These fault scarps are only slightly uplifted on the surface,which are usually difficult to identify by naked eyes,so they are also important reasons for the failure to discover them in time after the earthquake.The excavation of the trench reveals that the reverse fault dips south and the dip angle of the fault is only 20°,and the calculated average horizontal shortening offset is 1.51 to 1.76 m,and the average dip-slip offset is 1.61 to 1.87 m.Wuqia Basin South fault has the same active properties and equivalent offset as Kazikalte fault.The projection in the north-south direction of the maximum principal compressive stress shows that the two rupture zones are basically non-overlapping,which the strain energy in the western part of the epicenter was released by Wuqia Basin South fault ruptured and the strain energy in the east was released by Kazikalte fault ruptured,implies the close structural relationship between Wuqia Basin South fault and Kazikalte fault.These two faults are likely to merge into the same weak gypsum-salt detachment surface in depth,both of which belong to the thin skin structure of the Pamir subduction zone.
作者
胡伟华
常想德
陈建波
张勇
黄帅堂
伊力亚尔·阿不力孜
HU Wei-hua;CHANG Xiang-de;CHEN Jian-bo;ZHANG Yong;HUANG Shuai-tang;Yiliyaer Abulizi(Earthquake Agency of Xinjiang Uygur Autonomous Region,Urumqi 830011,Xinjiang,China)
出处
《内陆地震》
2021年第1期1-13,共13页
Inland Earthquake
基金
2020援疆项目—帕米尔—南天山交汇区场地模型建立与地震动区划(70020118).
