中国大陆M_S≥7.8大震的余震活动差异性特征及其成因研究
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摘要
文章以20世纪60年代以来中国大陆发生的4次MS≥7.8大震,即1970年云南通海7.8级、1976年河北唐山7.8级、2001年青海昆仑山口西8.1级和2008年四川汶川8.0级地震为研究对象,探讨了8级左右巨大地震的余震活动及分类,并以流变模型讨论了序列类型差异性的物理力学成因。初步给出:①4次大震的余震序列可归为两种类型,即低活动序列类型和高活动序列类型;②余震的差异性特征与主震孕育过程密切相联,理论模型和实际震例资料均给出,余震活动持续时间长短与大震孕震时间长短之间呈正相关变化;③根据对汶川8.0级大震的研究,孕震区介质流变性和构造变形速率的高低可能是造成大地震余震序列差异性特征的重要原因。
In this paper,by taking four MS≥7.8 earthquakes in China continent since the 1960s as research object,namely the 1970 Tonghai MS7.8 earthquake of Yunnan,the 1976 Tangshan MS7.8 earthquake of Hebei,the 2001 Kunlunshan Pass MS8.1 earthquake of Qinghai and the 2008 Wenchuan MS8.0 earthquake of Sichuan,we investigated the aftershock activity and its classification of great earthquakes around MS8.0,the physico-mechanical causes of the differentiated features among the types of aftershock sequences are also discussed based on the rheology model.Some preliminary conclusions are drawn: ① the types of aftershock sequences of the four large earthquakes can be divided into two categories,i.e.low activity sequence type and high activity sequence type;② the differentiated features of aftershock sequences are closely related to the process of the main shock preparation,the theoretical model and actual earthquake data both demonstrate that there is a positive correlation between the duration of aftershock activity and that of great shock preparation;③ in terms of the research on Wenchuan MS8.0 earthquake,the rheological property of media in seismogenic zone and the high or low velocity of tectonic deformation may be the important causes of the differentiated features among aftershock sequences of large earthquakes.
In this paper,by taking four MS≥7.8 earthquakes in China continent since the 1960s as research object,namely the 1970 Tonghai MS7.8 earthquake of Yunnan,the 1976 Tangshan MS7.8 earthquake of Hebei,the 2001 Kunlunshan Pass MS8.1 earthquake of Qinghai and the 2008 Wenchuan MS8.0 earthquake of Sichuan,we investigated the aftershock activity and its classification of great earthquakes around MS8.0,the physico-mechanical causes of the differentiated features among the types of aftershock sequences are also discussed based on the rheology model.Some preliminary conclusions are drawn: ① the types of aftershock sequences of the four large earthquakes can be divided into two categories,i.e.low activity sequence type and high activity sequence type;② the differentiated features of aftershock sequences are closely related to the process of the main shock preparation,the theoretical model and actual earthquake data both demonstrate that there is a positive correlation between the duration of aftershock activity and that of great shock preparation;③ in terms of the research on Wenchuan MS8.0 earthquake,the rheological property of media in seismogenic zone and the high or low velocity of tectonic deformation may be the important causes of the differentiated features among aftershock sequences of large earthquakes.
引文
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[5]张国民,邵志刚,刘桂萍,等.汶川8.0级地震构造动力成因分析[J].地震,2009,29(1):164-173.
[6]刘启元,陈九辉,李顺成,等.汶川MS8.0地震:川西流动地震台阵观测数据的初步分析[J].地震地质,2008,30(3):584-596.
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[8]张国民,傅征祥.华北强震的时间分布及物理解释[J].地球物理学报,1985,28(6):569-577.
[2]Kasahara K.Earthquake Mechanics[M].London:Cambridge University Press,1981.
[3]傅征祥.大地震的强余震活动持续时间和重复时间[J].地震地质,1990,11(4):15-20.
[4]张国民,李丽.地壳介质的流变性与孕震模型[J].地震地质,2003,25(1):1-10.
[5]张国民,邵志刚,刘桂萍,等.汶川8.0级地震构造动力成因分析[J].地震,2009,29(1):164-173.
[6]刘启元,陈九辉,李顺成,等.汶川MS8.0地震:川西流动地震台阵观测数据的初步分析[J].地震地质,2008,30(3):584-596.
[7]谷继成,谢小碧,赵莉.强余震的时空分布规律及其理论解释[J].地球物理学报,1979,22(2):32-46.
[8]张国民,傅征祥.华北强震的时间分布及物理解释[J].地球物理学报,1985,28(6):569-577.
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