2007年6月3日宁洱6.4级地震地表变形的构造分析和解释
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摘要
以2007年6月3日云南省宁洱6.4级地震地表裂缝、喷砂冒水、地震滑坡、地震崩塌等资料为基础,结合震区的地质构造、震源机制解、余震分布等资料,研究了本次地震的发震断层及其强震频繁发生的动力学机制.地震地表裂缝资料表明,北西向的宁洱断裂班海段具有右旋走滑的特征,北北东向的断层具有左旋走滑的性质.地震地质灾害集中分布在330°方向上的长13.5km、宽4km的范围内.等震线的长轴方向亦为330°,Ⅷ度区长轴长度为17km.震源机制解资料显示,宁洱6.4级地震的北西向节面为右旋错动,北东向节面为左旋错动.大于等于2.0级的余震分布优势方向为330°,深度为3—12km,优势深度为3—10km,余震分布与地震地质灾害集中分布带一致.以上资料说明,宁洱断裂班海段为这次地震的发震断层.最后以活动地块理论为基础,讨论了宁洱地震的动力来源为印度板块的向北推挤使青藏高原向东滑移,在滇西南地区转化为向南南东方向的挤出,使宁洱附近网络状的北西向断裂发生右旋活动,北东向断裂发生左旋活动.这种构造格局可能是该区频繁发生6.0—6.9级地震的原因.
The seismogenic fault and the dynamic mechanism of the Ning'er,Yunnan Province MS6.4 earthquake of June 3,2007 are studied on the basis of the observation data of the surface fissures,sand blow and water eruption,landslide and collapse associated with the earthquake,incorporating with the data of geologic structures,focal mechanism solutions and aftershock distribution for the earthquake area.The observation of the surface fissures reveals that the Banhai segment of the NW-trending Ning'er fault is dominated by right-lateral strike-slip,while the NNE-trending fault is dominated by left-lateral strike-slip.The seismo-geologic hazards are concentrated mainly within a 330°-extending zone of 13.5 km in length and 4 km in width.The major axis of the isoseismal is also oriented in 330° direction,and the major axis of the seismic intensity Ⅷ area is 13.5 km long.The focal mechanism solutions indicate that the NW-trending nodal plane of the Ning'er MS6.4 earthquake is dominated by right-lateral slip,while the NE-trending nodal plane is dominated by left-lateral slip.The preferred distribution orientation of the aftershocks of MS≥2 is 330°,and the focal depths are within the range of 3—12 km,predominantly within 3—10 km.The distribution of the aftershocks is consistent with the distribution zone of the seismo-geologic hazards.All the above-mentioned data indicate that the Banhai segment of the Ning'er fault is the seismogenic fault of this earthquake.Moreover,the driving force of the Ning'er earthquake is discussed in the light of the active block theory.It is believed that the northward pushing of the Indian plate has caused the eastward slipping of the Qinghai-Tibetan Plateau,which has been transformed into the southeastern-southernward squeezing of the southwest Yunnan region.As a result,the NW-trending faults in the vicinity of the Ning'er area are dominated by right-lateral strike-slip,while the NE-trending faults are dominated by left-lateral strike-slip.This tectonic framework might be the main cause of the frequent occurrence of MS6.0—6.9 earthquakes in the area.
The seismogenic fault and the dynamic mechanism of the Ning'er,Yunnan Province MS6.4 earthquake of June 3,2007 are studied on the basis of the observation data of the surface fissures,sand blow and water eruption,landslide and collapse associated with the earthquake,incorporating with the data of geologic structures,focal mechanism solutions and aftershock distribution for the earthquake area.The observation of the surface fissures reveals that the Banhai segment of the NW-trending Ning'er fault is dominated by right-lateral strike-slip,while the NNE-trending fault is dominated by left-lateral strike-slip.The seismo-geologic hazards are concentrated mainly within a 330°-extending zone of 13.5 km in length and 4 km in width.The major axis of the isoseismal is also oriented in 330° direction,and the major axis of the seismic intensity Ⅷ area is 13.5 km long.The focal mechanism solutions indicate that the NW-trending nodal plane of the Ning'er MS6.4 earthquake is dominated by right-lateral slip,while the NE-trending nodal plane is dominated by left-lateral slip.The preferred distribution orientation of the aftershocks of MS≥2 is 330°,and the focal depths are within the range of 3—12 km,predominantly within 3—10 km.The distribution of the aftershocks is consistent with the distribution zone of the seismo-geologic hazards.All the above-mentioned data indicate that the Banhai segment of the Ning'er fault is the seismogenic fault of this earthquake.Moreover,the driving force of the Ning'er earthquake is discussed in the light of the active block theory.It is believed that the northward pushing of the Indian plate has caused the eastward slipping of the Qinghai-Tibetan Plateau,which has been transformed into the southeastern-southernward squeezing of the southwest Yunnan region.As a result,the NW-trending faults in the vicinity of the Ning'er area are dominated by right-lateral strike-slip,while the NE-trending faults are dominated by left-lateral strike-slip.This tectonic framework might be the main cause of the frequent occurrence of MS6.0—6.9 earthquakes in the area.
引文
[1]云南省地质局.1976.普洱幅区域地质图(120万)及调查报告.
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云南省地质矿产局.1990.云南省区域地质志[M].北京:地质出版社:1--178.
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张培震,甘卫军,沈正康,王敏.2005.中国大陆现今构造作用的地块运动和连续变形耦合模型[J].地质学报,79(6):748--956.
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钟大赉,吴根耀,丁林.1998.藏东新生代陆内变形特征[G]∥潘裕生,孔祥儒主编.青藏高原岩石圈演化和动力学.广州:广东科技出版社:333--364.
周玖,黄修武.1980.在重力作用下我国西南地区地壳物质流[J].地震地质,2(4):1-10.
Minster J B,Jordan T H.1978.Present day plate motions[J].J Geophys Res,83:5331--5354.
Shen Zhengkang,Lu Jiangning,Wang Min,Burgmann R.2005.Contemporary crustal deformation aroundthe southeastborderland of the Tibetan Plateau[J].J Geophys Res,110(B11409),doi:10.1029/2004JB003421.
[2]云南省地质局.1983.思茅幅区域地质图(120万)及调查报告.
[1]陈慧,叶建庆,刘学军,付虹.2007.2007年云南宁洱6.4级地震监测与研究.
丁国瑜,卢演俦.1989.板内块体的现代运动[M]∥中国岩石圈动力学图集.北京:中国地图出版社:21.
邓起东,于贵华,叶文华.1992.地震地表破裂参数与震级关系的研究[G]∥《活动断裂研究》编委会编.活动断裂研究理论与应用,2期.北京:地震出版社:247--264.
邓起东,张培震,冉勇康,杨晓平,闵伟,楚全芝.2002.中国活动构造基本特征[J].中国科学(D辑),32(12):1020--1030.
邓起东,冉勇康,杨晓平,闵伟,楚全芝.2007.中国活动构造图(1400万)[M].北京:地震出版社.
虢顺民,汪洋,计凤桔.1999.云南思茅—普洱地区中强震群发生的构造机制[J].地震研究,22(2):105--114.
虢顺民,计凤桔,向宏发,董兴权,严富华,张双林,李新元,张晚霞.2001.红河活动断裂带[M].北京:海洋出版社:86--101.
龙海英,聂晓红,高国英.2007.新疆天山地区与川滇地区中强地震震源机制解对比分析[J].地震研究,30(3):229--234.
苗崇刚,胡永龙,周光全,侯建盛.2007.云南宁洱6.4级地震应急行动及灾害特征[J].国际地震动态,(6):5--11.
许志琴,候立玮,王宗秀.1992.中国松潘—甘孜造山带的造山过程[M].北京:地质出版社:1--190.
徐锡伟,闻学泽,郑荣章,马文涛,宋方敏,于贵华.2003.川滇地区活动块体最新构造变动样式及其动力来源[J].中国科学(D辑),33(3):281--288.
云南省地质矿产局.1990.云南省区域地质志[M].北京:地质出版社:1--178.
张培震,王琪,马宗晋.2002.中国大陆现今构造运动的GPS速度场与活动地块[J].地学前缘,9(2):430--441.
张培震,甘卫军,沈正康,王敏.2005.中国大陆现今构造作用的地块运动和连续变形耦合模型[J].地质学报,79(6):748--956.
郑斯华,高原.2001.青藏高原的地震学研究综述[G]∥马宗晋,汪一鹏,张燕平主编.青藏高原岩石圈现今变动与动力学.北京:地震出版社:223--239.
钟大赉,吴根耀,丁林.1998.藏东新生代陆内变形特征[G]∥潘裕生,孔祥儒主编.青藏高原岩石圈演化和动力学.广州:广东科技出版社:333--364.
周玖,黄修武.1980.在重力作用下我国西南地区地壳物质流[J].地震地质,2(4):1-10.
Minster J B,Jordan T H.1978.Present day plate motions[J].J Geophys Res,83:5331--5354.
Shen Zhengkang,Lu Jiangning,Wang Min,Burgmann R.2005.Contemporary crustal deformation aroundthe southeastborderland of the Tibetan Plateau[J].J Geophys Res,110(B11409),doi:10.1029/2004JB003421.
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