摘要
理塘断裂带沙湾段展布于四川西南部的木里河流域,处于理塘断裂带的南东尾端,为左旋走滑运动性质。文章在航空照片判译的基础上,通过野外研究发现,该断裂段的断错地貌现象主要集中分布在绒龙沟-沙湾的木里河东岸坡麓地带,表现为断层陡坎、断塞塘、断错冲沟、河流阶地及洪积扇等。由5个地点的断裂位错值和位错开始的年代学(TL和14C)测试结果,估计的该断裂段晚更新世以来的平均水平滑动速率为2.1±0.3mm/a。在该断裂上开挖的3个探槽资料表明,该断裂段存在史前强震的地质记录,最晚一次强震的发生时间介于1310±90～950±30aB.P.之间,强震所导致的垂直位错量约0.5m,同震水平位错1.30～1.45m左右。根据同震位错量及断裂长度估计的地震震级为7.0级左右。
Located at the drainage area of the Mull River in southeastern Sichuan of the southeastern margin of the Tibetan Plateau, the Shawan Segment is the SE ending section of the Litang Faults. It is about 20km long, characterized of sinistral strike-slip movement. Based on aerial photograph analysis and field investigation, the dislocation faulting landforms along the section have been found mainly on the hillside of the east bank of the Ronglonggou-Shawan section of the Muli River, in the forms of fault scarp, sag pond, dislocation gully （terrace and pluvial fan） and so on. The following important kinematic data were obtained： The fault scarp height is 0.3-10.0m. The sag pond size is 2m × 5m -50m × 200m. The Muli River was offset with a sinistral distance of 720m. The terrace Ⅱ ,Ⅲ and Ⅳ of the Muli River were offset with the sinistral distance of 70m, 160m and 320m respectively. The dislocation gullies were offset with a sinistral distance of 2.5 -50.0m, and two average sinistral offsets of 26m and 170m were found respectively on the lateral edge of its first-class alluvial-pluvial terrace and a dry-channel on the secondary-class alluvial-pluvial terrace. According to offset amount and offset-start geochronology （TL and ^14C） results from 5 sites on the section, the average horizontal slip rate along this fault is estimated as 2. 1 ± 0. 3mm/a. Data from 3 trenches at northwest of Haozidang, Xiaohaizi, and southeast of Haizidang, indicate that strong earthquakes existed, with the latest occurred between 1310 ±90 -950 ± 30aB. P. The perpendicular and horizontal slips caused by the latest earthquake are about 0.5m and 1.30 - 1.45m respectively, implying that the earthquake magnitude is about Ms 7.0. The current study has the importance for earthquake prediction and seismic hazard evaluation for the area of the Shawan Segment of the Litang Faults.
出处
《第四纪研究》
CAS
CSCD
北大核心
2007年第1期45-53,共9页
Quaternary Sciences
基金
国家自然科学基金项目(批准号:40372084)资助
关键词
理塘断裂带
滑动速率
断错地貌
史前强震
Litang Faults, slip rate, faulting landform, prehistoric strong earthquake
