2007年宁洱6.4级地震序列精定位
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摘要
2007年6月3日在云南宁洱发生6.4级地震,震后云南省地震局在主震附近架设了5套流动数字地震台。利用这些地震台和思茅固定地震台记录的震相数据,采用双差定位法对宁洱6.4级地震的余震序列重新进行精定位。结果显示,宁洱地震序列的长度约为40km,宽度约为10km,明显集中在普洱断裂与NNE向断裂横断错移的构造部位,且大部分余震发生在主震附近的普洱断裂。余震序列的优势分布方向明显,震源深度分布从浅层2km至12km,大多数集中在8～10km优势分布范围内,平均深度为7.9km,并且平行于地震序列剖面显示的地震破裂活动沿NW向倾斜,与NE向孟连-墨江断裂带在震区的次级断层倾向一致。地震在密集区的NW段比SE段要多,可能与当地的地下介质或断裂有关。垂直于地震序列剖面显示定位后地震主要密集分布在普洱断裂附近,地震序列的破裂活动沿SW方向倾斜,与普洱西支断裂倾向一致。总之,精定位后的断层走向和震源机制解的走向吻合得非常好,主震位于余震序列上端,余震在主震下端较为对称地分布,说明断层朝SE方向和NW方向破裂比较充分。
Five mobile digital seismic stations were set up by Earthquake Administration of Yunnan near the epicenter of the main shock after the Ning'er M6.4 earthquake on June 3,2007.In this paper,the aftershock sequence of the Ning'er M6.4 earthquake is relocated by using the double difference earthquake location method.The data are from the 5mobile digital seismic stations and the permanent Simao seismic station.The result shows that the length of aftershock sequence is 40km and the width is 30km,concentrated obviously at the lateral displacement area between the Pu'er fault and the NNE-trending faults,with the majority occurring on the Pu'er fault around the main shock.The depths of aftershocks are from 2km to 12km,and the predominant distribution is in the depth of 8～10km.The mean depth is 7.9km.The seismic fault dips to the northwest revealed from the profile parallel to this aftershock sequence,which is identical to the dip of the secondary fault of the NE-trending Menglian-Mojiang Fault in the earthquake area.There are more earthquakes concentrated in the northwest segment than in the southeast segment,which is perhaps related to the underground medium and faults.The depth profile of the earthquake sequence shows that the relocated earthquakes are mainly located near the Pu'er fault and the seismic ruptures dip to the southwest,consistent with the dip of the west branch of the Pu'er fault.In all,the fault strike showed by earthquake relocations matches well with the strike in the focal mechanism solutions.The main shock is in the top of the aftershock sequence and the aftershocks are symmetrically distributed,which shows that the faulting was complete in both NE and SW directions.
Five mobile digital seismic stations were set up by Earthquake Administration of Yunnan near the epicenter of the main shock after the Ning'er M6.4 earthquake on June 3,2007.In this paper,the aftershock sequence of the Ning'er M6.4 earthquake is relocated by using the double difference earthquake location method.The data are from the 5mobile digital seismic stations and the permanent Simao seismic station.The result shows that the length of aftershock sequence is 40km and the width is 30km,concentrated obviously at the lateral displacement area between the Pu'er fault and the NNE-trending faults,with the majority occurring on the Pu'er fault around the main shock.The depths of aftershocks are from 2km to 12km,and the predominant distribution is in the depth of 8～10km.The mean depth is 7.9km.The seismic fault dips to the northwest revealed from the profile parallel to this aftershock sequence,which is identical to the dip of the secondary fault of the NE-trending Menglian-Mojiang Fault in the earthquake area.There are more earthquakes concentrated in the northwest segment than in the southeast segment,which is perhaps related to the underground medium and faults.The depth profile of the earthquake sequence shows that the relocated earthquakes are mainly located near the Pu'er fault and the seismic ruptures dip to the southwest,consistent with the dip of the west branch of the Pu'er fault.In all,the fault strike showed by earthquake relocations matches well with the strike in the focal mechanism solutions.The main shock is in the top of the aftershock sequence and the aftershocks are symmetrically distributed,which shows that the faulting was complete in both NE and SW directions.
引文
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马杏垣,丁国瑜,高文学,等.1989.中国岩石圈动力学地图集[M].北京:中国地图出版社.MA Xing-yuan,DING GUO-yu,GAO Wen-xue,et al.1989.Lithospheric Dynamics Atlas of China[M].Sinomaps Press,Beijing(in Chinese).
钱晓东,李琼,秦嘉政.2007.2007年宁洱6.4级地震序列视应力研究[J].地震研究,30(4):311—317.QIAN Xiao-dong,LI Qiong,QIN Jia-zheng.2007.Apparent stress of the2007Ning'er,Yunnan,MS6.4earthquake se-quence[J].Journal of Seismological Research,30(4):311—317(in Chinese).
汪晓,赵国泽,汤吉,等.2008.宁洱地震区深部电性结构及发震构造初析(Ⅰ)[J].地震地质,30(2):516—524.WANG Xiao,ZHAO Guo-ze,TANG Ji,et al.2008.Preliminary analyses of the deep electrical structure and decollement structure in Ning'er seismic area-I[J].Seismology and Geology,30(2):516—524(in Chinese).
谢富仁,苏刚,崔效锋,等.2001.滇西南地区现代构造应力场分析[J].地震学报,23(1):17—23.XIE Fu-ren,SU Gang,CUI Xiao-feng,et al.2001.Modern tectonic stress field in southwestern Yunnan,China[J].Ac-ta Seismologica Sinica,23(1):17—23(in Chinese).
谢英情,李岩峰,张建国,等.2007.2007年宁洱6.4级地震发震构造分析[J].地震研究,30(4):350—358.XIE Ying-qing,LI Yan-feng,ZHANG Jian-guo,et al.2007.Seismogenic structure of the2007Ning'er,Yunnan,MS6.4earthquake[J].Journal of Seismological Research,30(4):350—358(in Chinese).
徐锡伟,闻学泽,郑荣章,等.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.XU Xi-wei,WEN Xue-ze,ZHENG Rong-zhang,et al.2003.Pattern of latest tectonic motion and its dynamics for active blocks in Sichuan-Yunnan region,China[J].Science in China(Ser D),33(3):281—288(in Chinese).
徐彦,杨晶琼,苏有锦,等.2005.云南地区地震精确定位及其构造意义分析[J].地震研究,28(4):340—344.XU Yan,YANG Jing-qiong,SU You-jin,et al.2005.Analysis on accurate location of earthquakes in Yunnan area and its tectonic meaning[J].Earthquake Research in China,28(4):340—344(in Chinese).
张勇,许力生,陈运泰,等.2008.2007年云南宁洱MS6.4地震震源过程[J].中国科学(D辑),38(6):683—692.ZHANG Yong,XU Li-sheng,CHEN Yun-tai,et al.2008.Tempo-spatial rupture process of the2007MS6.4Ning'er earthquake[J].Science in China(Ser D),38(6):683—692(in Chinese).
Waldhauser F and Ellsworth W L.2000.A double-difference earthquake location algorithm:Method and application to the northern Hayward Fault,California[J].Bulletin of the Seismological Society of America,90(6):1353—1368.
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—115.GUO Shun-min,WANG Yang,JI Feng-ju.1999.Tectonic mechanism of moderate-strong earthquake swarms in Yunnan's Simao-Pu'er region[J].Journal of Seismological Research,22(2):105—115(in Chinese).
李永华,吴庆举,田小波,等.2009.用接收函数方法研究云南及其邻区地壳上地幔结构[J].地球物理学报,52(1):67—80.LI Yong-Hua,WU Qing-ju,TIAN Xiao-bo,et al.2009.Crustal structure in the Yunnan region determined by modeling receiver functions[J].Chinese Journal of Geophysics,52(1):67—80(in Chinese).
李忠华,苏有锦,蔡明军,等.1999.云南地区震源破裂长度与震级的经验公式[J].西北地震学报,21(3):31—33.LI Zhong-hua,SU You-jin,CAI Ming-jun,et al.1999.Empirical relationships between magnitude and source rupture length in Yunnan[J].Northwestern Seismological Journal,21(3):31—33(in Chinese).
刘丽芳,苏有锦,秦嘉政,等.2007.2007年宁洱6.4级地震序列及中短期地震学异常演化特征研究[J].地震研究,30(4):324—330.LIU Li-fang,SU You-jin,QIN Jia-zheng,et al.2007.2007Ning'er,Yunnan,MS6.4earthquake sequence characteristics and its medium-short term seismological anomalies[J].Journal of Seismological Research,30(4):324—330(in Chinese).
马杏垣,丁国瑜,高文学,等.1989.中国岩石圈动力学地图集[M].北京:中国地图出版社.MA Xing-yuan,DING GUO-yu,GAO Wen-xue,et al.1989.Lithospheric Dynamics Atlas of China[M].Sinomaps Press,Beijing(in Chinese).
钱晓东,李琼,秦嘉政.2007.2007年宁洱6.4级地震序列视应力研究[J].地震研究,30(4):311—317.QIAN Xiao-dong,LI Qiong,QIN Jia-zheng.2007.Apparent stress of the2007Ning'er,Yunnan,MS6.4earthquake se-quence[J].Journal of Seismological Research,30(4):311—317(in Chinese).
汪晓,赵国泽,汤吉,等.2008.宁洱地震区深部电性结构及发震构造初析(Ⅰ)[J].地震地质,30(2):516—524.WANG Xiao,ZHAO Guo-ze,TANG Ji,et al.2008.Preliminary analyses of the deep electrical structure and decollement structure in Ning'er seismic area-I[J].Seismology and Geology,30(2):516—524(in Chinese).
谢富仁,苏刚,崔效锋,等.2001.滇西南地区现代构造应力场分析[J].地震学报,23(1):17—23.XIE Fu-ren,SU Gang,CUI Xiao-feng,et al.2001.Modern tectonic stress field in southwestern Yunnan,China[J].Ac-ta Seismologica Sinica,23(1):17—23(in Chinese).
谢英情,李岩峰,张建国,等.2007.2007年宁洱6.4级地震发震构造分析[J].地震研究,30(4):350—358.XIE Ying-qing,LI Yan-feng,ZHANG Jian-guo,et al.2007.Seismogenic structure of the2007Ning'er,Yunnan,MS6.4earthquake[J].Journal of Seismological Research,30(4):350—358(in Chinese).
徐锡伟,闻学泽,郑荣章,等.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.XU Xi-wei,WEN Xue-ze,ZHENG Rong-zhang,et al.2003.Pattern of latest tectonic motion and its dynamics for active blocks in Sichuan-Yunnan region,China[J].Science in China(Ser D),33(3):281—288(in Chinese).
徐彦,杨晶琼,苏有锦,等.2005.云南地区地震精确定位及其构造意义分析[J].地震研究,28(4):340—344.XU Yan,YANG Jing-qiong,SU You-jin,et al.2005.Analysis on accurate location of earthquakes in Yunnan area and its tectonic meaning[J].Earthquake Research in China,28(4):340—344(in Chinese).
张勇,许力生,陈运泰,等.2008.2007年云南宁洱MS6.4地震震源过程[J].中国科学(D辑),38(6):683—692.ZHANG Yong,XU Li-sheng,CHEN Yun-tai,et al.2008.Tempo-spatial rupture process of the2007MS6.4Ning'er earthquake[J].Science in China(Ser D),38(6):683—692(in Chinese).
Waldhauser F and Ellsworth W L.2000.A double-difference earthquake location algorithm:Method and application to the northern Hayward Fault,California[J].Bulletin of the Seismological Society of America,90(6):1353—1368.
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