摘要
作为 1996年丽江 7.0级地震的发震断层 ,丽江—大具断裂可以分为丽江—玉湖和玉湖—大具等南北两段 .它们在构造表现、运动方式等方面都存在明显差异 ,但都表现出比较一致的运动学性质 ,即既具有垂直正断运动 ,又有水平左旋走滑运动 .这种运动特征开始于第四纪初期 (距今 2 .4～ 2 .5Ma) .在构造形式上 ,早更新世时期发育低倾角拆离断层 ;中更新世(0 .8Ma)以来 ,以高角度正断层活动为主 .根据源于玉龙—哈巴雪山东麓的一系列冲沟 ,在穿越山前断裂时同步左旋位错特点和剥夷面垂直落差 ,初步估算了丽江—大具断裂第四纪以来的平均水平和垂直位错速率分别为 0 .84和 0 .70mm/a ;中更新世以来的平均水平和垂直位错速率分别为 1.5 6和 1.6 9mm/a .近南北向丽江—大具断裂的运动性质一方面受到区域性北北西 南南东水平主压应力场的影响 ;另一方面 ,也受到玉龙—哈巴雪山与丽江盆地之间强烈的差异性运动的制约 .这两种动力学过程的共同作用 ,形成了 1996年丽江地震构造环境的特色 .
Lijiang-Daju fault,the seismogenic fault of the 1996 Lijiang M =7.0 earthquake,can be divided into Lijiang-Yuhu segment in the south and Yuhu-Daju segment in the north. The two segments show clear difference in geological tectonics, but have the similar dynamic features. Both normal dip-slip and sinistral strike-slip coexist on the fault plane. This kind of movement started at the beginning of the Quaternary (2.4～2.5 Ma B.P.). As to the tectonic types,the detachment fault with low angle was developed in the Early Pleistocene and the normal fault with high angle only after the mid-Pleistocene (0.8 Ma B.P.). Based on the horizontal displacements of gullies and the vertical variance of planation surfaces cross the Lijiang-Daju fault at east piedmont of Yulong-Haba range,the average horizontal and vertical slip rates are calculated. They are 0.84 mm/a and 0.70 mm/a since the Quaternary and 1.56 mm/a and 1.69 mm/a since the mid-Pleistocene. The movements of the nearly N-S-trending Lijiang-Daju fault are controlled not only by the regional stress field,but also by the variant movement between the Yulong-Haba range and Lijiang basin. The two kinds of dynamic processes form the characteristics of seismotectonic environment of occurring the 1996 Lijiang earthquake.
出处
《地震学报》
CSCD
北大核心
2004年第4期410-418,共9页
Acta Seismologica Sinica
基金
地震科学联合基金 (1980 2 3)
国家自然科学基金 (4 0 2 72 0 87)资助
关键词
1996年丽江地震
差异运动
盆地边界断裂
地震构造环境
the 1996 Lijiang earthquake
variant movement
basin boundary fault
seismotectonic environment
