地震地质 ›› 2005, Vol. 27 ›› Issue (2): 234-242.

• 研究论文 • 上一篇    下一篇

利用岷江阶地的变形估算龙门山断裂带中段晚第四纪滑动速率

马保起, 苏刚, 侯治华, 舒赛兵   

  1. 中国地震局地壳应力研究所, 北京, 100085
  • 收稿日期:2004-05-25 修回日期:2004-09-04 出版日期:2005-06-02 发布日期:2009-10-26
  • 作者简介:马保起,男,1965年生,2000年在北京大学获得地貌学与第四纪地质学专业博士学位,副研究员,现在主要从事地震地质学与地貌学的研究工作,电话:010-62842635,E-mail:mabq1965@yahoo.com.cn.
  • 基金资助:
    地震科学联合基金(198050和101096)资助。

LATE QUATERNARY SLIP RATE IN THE CENTRAL PART OF THE LONGMENSHAN FAULT ZONE FROM TERRACE DEFORMATION ALONG THE MINJIANG RIVER

MA Bao-qi, SU Gang, HOU Zhi-hua, SHU Sai-bing   

  1. Institute of Crustal Dynamics, China Earthquake Administration, Beijing 100085, China
  • Received:2004-05-25 Revised:2004-09-04 Online:2005-06-02 Published:2009-10-26

摘要: 用岷江都江堰—汶川段晚第四纪阶地面的变形量估算了龙门山断裂带中段的滑动速率。岷江及其支流发育3级晚第四纪河流阶地,阶地面的年龄分别约为10,20,50kaBP。阶地纵剖面在茂汶-汶川断裂、北川-映秀断裂和江油-灌县断裂处有明显的垂直变形。断裂活动具有间歇性特点,晚第四纪以来有过3期活动,其起始时间分别为50,20,10kaBP。依据各级阶地面年龄和变形量估算的茂汶-汶川断裂、北川-映秀断裂和江油-灌县断裂晚第四纪逆冲滑动速率分别为0.5,0.6~0.3,0.2mm/a;据阶地走滑位错估算的茂汶-汶川断裂和北川-映秀断裂的晚第四纪右旋走滑速率均约为1mm/a。现代河床之下发育很厚的河流堆积物表明,龙门山的构造抬升经历了较为复杂的过程。

关键词: 龙门山断裂带, 岷江阶地, 晚第四纪, 断裂滑动速率

Abstract: We estimate the slip rates of three faults in the central segment of Longmenshan Fault zone, namely, the Maowen-Wenchuan Fault, the Beichuan-Yingxiu Fault and the Jiangyou-Guanxian Fault, based on the measurement and dating of deformation of Late Quaternary terraces along the Minjiang River and its tributaries. The three-level Late Quaternary terraces, T1, T2 and T3, are well developed along the Dujiangyan-Wenchuan reach of the Minjiang River. The cross profiles show that T3 and T1 have undergone a complete development process. The thermoluminescence ages of the upper deposits on T1, T2 and T3 are 9~13ka BP, 19~30(ka BP) and 51~58ka BP, respectively. Therefore, we can constrain the ages of T1, T2 and T3 surfaces to 10ka BP, 20ka BP and 50ka BP, respectively. The synchronous three-level terraces also exist in the valleys of the Baishahe River and other tributaries of the Minjiang River. These river terraces are laterally and vertically dislocated by the Longmenshan Fault zone. According to the dating and vertical displacements of river terraces, the Late Quaternary reverse slip rates of the Maowen-Wenchuan Fault, the Beichuan-Yingxiu Fault and the Jiangyou-Guanxian Fault are estimated to be 0.5mm/a, 0.6~0.3mm/a, 0.2mm/a, respectively. According to the lateral displacements of river terraces, the Late Quaternary dextral strike-slip rate of the Maowen-Wenchuan Fault and the Beichuan-Yingxiu Fault averages 1mm/a each. The late Quaternary faulting of the Longmenshan Fault zone is characterized with intermittency. Three faulting stages can be identified. The first one is between 50ka BP to 20ka BP, the second one between 20ka BP to 10ka BP, and the latest starts at 10ka BP. The existence of thick alluvial deposits in the present channel indicates that the uplift of Longmenshan Mountains is more complex than previously estimated.

Key words: Longmenshan Fault zone, Minjiang river terrace, late Quaternary, fault slip rate

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