西北地震学报2013，Vol.35Issue(2)：342-353,12.DOI:10.3969/j.issn.1000-0844.2013.02.0342
滇西南地区黑河断裂中西段晚第四纪构造活动特征
Characteristics of Late Quaternary Tectonic Activity of Middle-western Segment of Heihe Fault in Southwestern Part of Yunnan Province
摘要
Abstract
On November 6,1988,two earthquakes with a magnitude ＞7 occurred in the Lancang and Gengma area of the southwestern part of the Yunnan province.The maximum intensity of the M7.6 Lancang earthquake was Ⅸ on the Chinese scale,which is similar to the Modified Mercalli scale.The surface rupture of the tectonic activity of the Lancang Ms7.6 earthquake occurred because of the earthquake-related extensional ground cracks and small fault scarps in the epicentral region.The area within which the cracks and small scarps occurred was approximately 35-km long and 3-km wide.The maximum vertical and the dextral horizontal offsets were 1.5 m and 1.4 m,respectively.The M7.6 earthquake showed complicated earthquake-generating tectonics and formed a separate obvious seismic deformation belt along the Heihe and Lancang faults.The Heihe fault is one of the seismogenic faults of the 1988 M7.6 event of Lancang.The Heihe fault,located in the southwestern part of the Yunnan province,having a length of 168 km and a trend of 280°～310°,is an active fault zone in the late Quaternary,which is mainly a right-lateral strike slip with a dip slip.It turns out that the Heihe fault zone can be divided into three secondary fault segments,namely,Cangyuan-Mujia(F1-1),Mujia-Nandai(F1-2),and Nandai-Mengwang(F1-3).The activity gradually becomes weak when this segment of fault travels eastward.Through satellite image interpretation and field geological investigation,we studied the geological and geomorphologic characteristics of activity along the middle and the western segments of the Heihe fault in this research.The middle and western segments of the Heihe fault,having a length of 88 km and a trend of 280°～310°,is an active fault zone in the late Quaternary,which is mainly a right-lateral strike slip with a dip slip.A variety of dislocation landforms have been formed along the fault by the new tectonic activities since the late Quaternary,such as the dextral dislocation of gullies and ridges,fault trenches,fault passes,fault scarps,and pits.A series of dextral dislocations of gullies and ridges,and scratches on the cross section along the fault show that the middle-western segment on the Heihe fault is dominated by a right-lateral strike slip.In the Xuelidazai village,the age of the displaced stratum is(2 530±25)a.B.P.,and on the fault plane,a loosely consolidated gouge is developed across several cross sections of the fault.This implies that the latest active time of the middle-western segment on the Heihe fault is the late Holocene.Near Baishuijing,there are synchronous dextral dislocations of four small gullies because of the dextral movement of faults; these dislocations range from 9 to 14 m.By using the differential GPS measurement,the sample dating and the regional comparison of the fault slip rate,we calculated the right-lateral strike slip rate of the segment to be(3.54 ± 0.78)mm/a.This value agrees with the regional characteristics of the fault slip rate.关键词
黑河断裂/晚第四纪/活动断裂/右旋走滑/滑动速率Key words
Heihe fault/ Late Quaternary/ Active tectonics/ Right-lateral strike-slip motion/ Slip rate分类
天文与地球科学引用本文复制引用
方良好,袁道阳,邵延秀,何文贵,刘兴旺,张波..滇西南地区黑河断裂中西段晚第四纪构造活动特征[J].西北地震学报,2013,35(2):342-353,12.基金项目
公益性行业科研专项(201108001) （201108001）
