1996年2月3日云南丽江7.0级地震发生的构造环境
|
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.
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.
引文
①云南省地质局.1977.区域地质调查报告.
陈文寄,HarrisonTM ,LoveraOM .1992.哀牢山—红河剪切带的热年代学研究[J].地震地质,14(2):122～128
崔之久,伍永秋,刘耕年,等.1996.昆仑山垭口地区晚新生代以来的气候构造事件[A].见:青藏项目专家组编.青藏高原形成演化、环境变迁与生态系统研究[C].北京:科学出版社,74～84
邓起东.1991.活动断裂研究的进展和方向[A].见:中国地震局科技发展司“活动断裂研究”编委会编.活动断裂研究(1)[C].北京:地震出版社,1～6
国家地震局地质研究所,云南省地震局.1990.滇西北地区活动断裂[M].北京:地震出版社,321
马宗晋,张家声,汪一鹏.1998.青藏高原三维变形运动学的时段划分和新构造分区[J].地质学报,72(3):211～227
秦嘉政,刘祖荫,张俊伟.1997.用地震标定律研究丽江7.0级地震的破裂过程[J].地震研究,20(1):47～57
沈军,汪一鹏,任金卫.2001.中国云南德钦—中甸—大具断裂带第四纪右旋走滑运动[A].见:马宗晋等主编.青藏高原岩石圈现今变动与动力学[M].北京:地震出版社,123～135
王绍晋,龙晓帆,罗淑进.1997.丽江地震序列的震源机制、发震应力场和破裂特征[J].地震研究,20(1):26～34
向宏发,徐锡伟,虢顺民,等.2002.丽江—小金河断裂第四纪以来的左旋逆推运动及其构造地质意义[J].地震地质,24(2):188～198
张家声,韩竹军.2001.滇西北玉龙—哈巴雪山的递进变形、FT年代和区域构造联系[A].见:马宗晋等主编.青藏高原岩石圈现今变动与动力学[M].北京:地震出版社,136～147
张建国,周瑞琦,吴伯黔.1997.丽江7.0级地震地表破裂与形变特征[J].地震研究,20(1):58～65
YeatsRS ,SiehK ,AllenC .1997.TheGeologyofEarthquake[M].NewYork:OxfordUniversityPress,249～300
陈文寄,HarrisonTM ,LoveraOM .1992.哀牢山—红河剪切带的热年代学研究[J].地震地质,14(2):122～128
崔之久,伍永秋,刘耕年,等.1996.昆仑山垭口地区晚新生代以来的气候构造事件[A].见:青藏项目专家组编.青藏高原形成演化、环境变迁与生态系统研究[C].北京:科学出版社,74～84
邓起东.1991.活动断裂研究的进展和方向[A].见:中国地震局科技发展司“活动断裂研究”编委会编.活动断裂研究(1)[C].北京:地震出版社,1～6
国家地震局地质研究所,云南省地震局.1990.滇西北地区活动断裂[M].北京:地震出版社,321
马宗晋,张家声,汪一鹏.1998.青藏高原三维变形运动学的时段划分和新构造分区[J].地质学报,72(3):211～227
秦嘉政,刘祖荫,张俊伟.1997.用地震标定律研究丽江7.0级地震的破裂过程[J].地震研究,20(1):47～57
沈军,汪一鹏,任金卫.2001.中国云南德钦—中甸—大具断裂带第四纪右旋走滑运动[A].见:马宗晋等主编.青藏高原岩石圈现今变动与动力学[M].北京:地震出版社,123～135
王绍晋,龙晓帆,罗淑进.1997.丽江地震序列的震源机制、发震应力场和破裂特征[J].地震研究,20(1):26～34
向宏发,徐锡伟,虢顺民,等.2002.丽江—小金河断裂第四纪以来的左旋逆推运动及其构造地质意义[J].地震地质,24(2):188～198
张家声,韩竹军.2001.滇西北玉龙—哈巴雪山的递进变形、FT年代和区域构造联系[A].见:马宗晋等主编.青藏高原岩石圈现今变动与动力学[M].北京:地震出版社,136～147
张建国,周瑞琦,吴伯黔.1997.丽江7.0级地震地表破裂与形变特征[J].地震研究,20(1):58～65
YeatsRS ,SiehK ,AllenC .1997.TheGeologyofEarthquake[M].NewYork:OxfordUniversityPress,249～300
版权所有：© 2023 中国地质图书馆 中国地质调查局地学文献中心