SEISMOLOGY AND GEOLOGY ›› 2014, Vol. 36 ›› Issue (4): 1260-1279.DOI: 10.3969/j.issn.0253-4967.2014.04.025

• CONTENTS • Previous Articles     Next Articles

LATE-QUATERNARY ACTIVITY OF THE ZHAOTONG-LUDIAN FAULT ZONE AND ITS TECTONIC IMPLICATION

CHANG Zu-feng1, ZHOU Rong-jun2, AN Xiao-wen1, CHEN Yu-jun1, ZHOU Qing-yun1, LI Jian-lin1   

  1. 1. Earthquake Administration of Yunnan Province, Kunming 650041, China;
    2. Earthquake Administration of Sichuan Province, Chengdu 610041, China
  • Received:2014-11-10 Online:2014-12-30 Published:2015-01-07

昭通-鲁甸断裂晚第四纪活动及其构造意义

常祖峰1, 周荣军2, 安晓文1, 陈宇军1, 周青云1, 李鉴林1   

  1. 1. 云南省地震局, 昆明 650041;
    2. 四川省地震局, 成都 610041
  • 作者简介:常祖峰,男,1966年生,1987年毕业于北京大学地震地质专业,1999年在北京大学地质系获硕士学位,高级工程师,主要从事地震地质和工程地震等方面的研究,电话:0871-63373589,E-mail:zufch@163.com.
  • 基金资助:

    中国地震局地震行业科研专项(201108001)和中国地质调查局"南北构造带活动构造体系综合调查与研究"(12120114002101)共同资助

Abstract:

The Zhaotong-Ludian Fault zone, composed mainly of three right-step en echelon faults, namely, the Zhaotong-Ludian Fault, the Sayuhe Fault and the Longshu Fault, strikes 40°~60° on the whole, with the Sayuhe Fault and the Longshu Fault dipping SE and the Zhaotong-Ludian Fault dipping NW, and they all together constitute a complicated thrust fault system. Based on years of field investigation results of geology and geomorphography, we elaborate the late Quaternary active features, the geological and geomorphic evidences of the latest activity of the Zhaotong-Ludian Faults. Our observation shows that: the late Cenozoic basins along the Zhaotong-Luian Fault zone are obviously dominated by the fault; there are many neo-active fault landforms, such as, flat and straight fault troughs, directional aligned fault facets and fault scarps, and the upper Pleistocene to Holocene strata are offset by the fault. The fault zone has been active since the late Quaternary. For example, the fault at Daqiaobian dislocated a set of strata of the Pliocene, and middle to upper Pleistocene, with an apparently reverse character. The fault trending NE is developed in the Holocene diluvium with oblique striation on the fault plane at Guangming Village. Deposits with an OSL age of(23.4±1.8)ka BP on T2 terrace of a small river near Beizha town was offset by the fault. There is a fault scarp trending NE 40°, 0.5~2.0m in height, on the first terrace of the Longshu River near the Longshu Village. Several Quaternary faults are revealed by the trench which offset the late Pleistocene to Holocene strata and there are three poleo-earthquake events discovered in the trench. At Yanjiao Village the gravel layer has risen steeply and is aligned in a line because of squeezing effect of the fault; the rivers and ridges nearby are synchronously offset dextrally up to 30~40m. The fault zone is dominated by reverse faulting with a small amount of right-lateral motion. Besides, there are some NW-trending faults interweaving with the NE-trending fault zone, some of which are active since late Quaternary as well, and they are the conjugate structures with the NE-trending faults. Surface deformation, such as NE- and NW-trending ground fissures and reverse scarp landforms, has been generated in the epicenter area of the 2014 Ludian M6.5 earthquake, the distribution of which is in consistence with the NE- and NW-trending faults. Because of far-field deformation response and energy exchange and transfer between blocks, the Liangshan active sub-block formed on the east of the Sichuan-Yunnan block, and the Zhaotong-Ludian Fault zone lies in the forefront of the SE movement of this sub-block. On account of its distinct location and its complicated geometric structure, the Zhaotong-Ludian Fault zone is one of main carriers of the tectonic deformation of the Liangshan active sub-block to absorb and accommodate the strains produced by the block's SE movement, and is the southern boundary of the Liangshan sub-block. From the point of view of the regional tectonic positions and the kinematic characteristics, the relation of Zhaotong-Ludian Fault zone to the Liangshan active sub-block is exactly as the relation of the Longmanshan Faults to Bayan Har block. Consequently, the Zhaotong-Ludian Fault zone has an important significance in the division of active block boundaries and the regional tectonic framework, and meanwhile, it is also an important seismogenic structure in the northeastern Yunnan.

Key words: Zhaotong-Ludian Fault, late-Quaternary activity, Liangshan sub-block, thrust movement, tectonic implication

摘要:

昭通-鲁甸断裂带主要由昭通-鲁甸、洒渔河和龙树3条右阶斜列的断裂组成.总体走向40°~60°, 洒渔河和龙树断裂倾向SE, 昭通-鲁甸断裂倾向NW, 它们共同构成几何结构复杂的逆冲断裂系.野外考察表明:沿断裂表现为平直的断层槽地、定向排列的断层三角面、断层陡坎等地貌;大桥边、北闸镇、光明村等地断错了晚更新世—全新世地层;龙树河Ⅰ级阶地上发育高0.5~2.0m的断层陡坎.表明其最新活动时代为晚更新世—全新世, 运动性质以逆冲运动为主兼有右旋走滑分量.此外, 在NE向断裂间穿插发育的一些NW向断裂, 同样表现出晚第四纪活动特征.在2014年鲁甸M6.5地震震区产生了NE和NW向地裂缝和地形反坎等地表形变, 与NE和NW向断裂展布基本一致, 反映了断裂的新活动特征.由于块体远程变形响应与能量交换传递, 在川滇块体东侧形成了凉山次级活动块体, 昭通-鲁甸断裂带位于凉山次级活动块体SE向运动的前缘部位.它独特的地理位置和复杂的断裂几何结构成为凉山次级块体构造变形的主要承载体之一, 吸收、调节块体SE向运动应变, 并构成了凉山次级活动块体的南部边界.从区域构造部位和运动特征分析, 昭通-鲁甸断裂带之于凉山次级块体, 正如龙门山断裂带之于巴颜喀拉块体.昭通-鲁甸断裂带在活动块体边界和区域构造格架划分上具有重要的构造意义, 同时也是滇东北地区重要的地震构造.

关键词: 昭通-鲁甸断裂, 晚第四纪活动, 凉山次级块体, 逆冲运动, 构造意义

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