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
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摘要
分析了2007年6月3日云南宁洱6.4级地震序列基本特征,动态追踪了宁洱地震前的中短期地震学异常,结果表明:宁洱地震序列为主震—余震型,最大余震为5.1级,衰减正常。据云南区域数字地震台网资料测定,震源机制解中节面Ⅰ走向为138°,倾角为70°,P轴方位为3°,仰角为9°,宁洱6.4级地震的发震断层为NNW向的普(宁)洱断裂,在NNE向主压应力作用下产生右旋走滑错动,引发宁洱地震。宁洱地震孕育的中短期阶段,地震学异常以云南M≥6.0地震平静和震中附近中小地震活动增强等为主;地震孕育进入短临阶段,最为突出的地震学异常为震源区及附近地区中小地震活动明显增强、出现窗口地震及云南省4级地震平静等。
We analyzed the basic features of the 2007 Ning'er MS6.4 earthquake sequence and dynamically traced medium-and short-term seismological anomalies of the Ning'er earthquake befor the shock. The Ning'er earthquake is mainshock-aftershock type. The largest aftershock was MS5.1 and the aftershock sequence attenuated normally. The focal mechanism solutions were calculated by using the data of Yunnan Regional Digital Seismic Network. The result indicates that the strike of the nodal planeⅠis 138°,the dip angle is 70°, the azimuth of the P-axis is 3°,and the elevation angle is 9°. The seismogenic structure of the Ning'er MS6.4 earthquake is the Pu'er(Ning'er)fault in NNW direction,and the earthquake is the result of the dextral strike-slip of the fault under NNE-direction horizontal principal compressive stress. In the medium-and short-term stage of the Ning'er earthquake preparation,M≥6.0 earthquake quiescence appeared and the moderate-small earthquakes increased around the epicenter. In the short-impending stage,the moderate-small earthquake activity strengthened obviously in the source area and nearby,the window earthquakes occurred,and M≥4 earthquake quiescence of Yunnan appeared.
We analyzed the basic features of the 2007 Ning'er MS6.4 earthquake sequence and dynamically traced medium-and short-term seismological anomalies of the Ning'er earthquake befor the shock. The Ning'er earthquake is mainshock-aftershock type. The largest aftershock was MS5.1 and the aftershock sequence attenuated normally. The focal mechanism solutions were calculated by using the data of Yunnan Regional Digital Seismic Network. The result indicates that the strike of the nodal planeⅠis 138°,the dip angle is 70°, the azimuth of the P-axis is 3°,and the elevation angle is 9°. The seismogenic structure of the Ning'er MS6.4 earthquake is the Pu'er(Ning'er)fault in NNW direction,and the earthquake is the result of the dextral strike-slip of the fault under NNE-direction horizontal principal compressive stress. In the medium-and short-term stage of the Ning'er earthquake preparation,M≥6.0 earthquake quiescence appeared and the moderate-small earthquakes increased around the epicenter. In the short-impending stage,the moderate-small earthquake activity strengthened obviously in the source area and nearby,the window earthquakes occurred,and M≥4 earthquake quiescence of Yunnan appeared.
引文
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Snoke J A,Munsey J W,Teague A G,et al.1984.A program forfocal mechanism determination by combined use of polarity andSV2P amplitude ratio data[J].Earthquake Notes,55(3):15.
Snoke J A.1989.Earthquake mechanism[A].in:James D E.Encyclopedia of Geophysics[C].New York:Van NostrandReinhold Company,239-245.
付虹,王炜,王世芹,等.2002.地震活动因子A值在川滇地区M≥6地震中短期预报中的应用[J].内陆地震,16(3):205-212.
郭增建,秦保燕.1979.震源物理[M].北京:地震出版社,55-58.
和宏伟,秦嘉政,石绍先,等.2002.云南中强震前4级地震活动平静特征研究[J].地震研究,25(增刊B):55-63.
胡小幸,林邦慧.1989.邢台地震空间分布随时间变化的立体图像与地震发生过程[J].地震学报,11(1):1-11.
刘杰,郑斯华,康英,等.2004.利用P波和S波的初动和振幅比计算中小地震的震源机制解[J].地震,24(1):19-24.
毛玉平,韩新民.2003.云南地区强震(M≥6)研究[M].昆明:云南科技出版社.
王炜,刘峥.1999.地震活动性的定量化及其在地震中期预报中的应用[J].中国地震,15(2):116-127.
中国地震局监测预报司.2005.西南地区强地震短期前兆特征和预测方法研究[M].北京:地震出版社.
Snoke J A,Munsey J W,Teague A G,et al.1984.A program forfocal mechanism determination by combined use of polarity andSV2P amplitude ratio data[J].Earthquake Notes,55(3):15.
Snoke J A.1989.Earthquake mechanism[A].in:James D E.Encyclopedia of Geophysics[C].New York:Van NostrandReinhold Company,239-245.