云南地区数字地震波波速比的区域特征
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摘要
从1998~2006年间云南地区数字地震台网记录中,选用有4个以上台记录到的震相清晰的直达Pg波、Sg波的到时(包含Pg、Sg的到时差在20~25 s的远台和小于0.5 s的近台),计算出云南地区数字地震波的波速比(VP/VS),并分析了其区域分布特征。结果表明:1998~2006年云南地区波速比月均值为1.685,滇西南地区的月均值高于云南地区的月均值;滇西地区的月均值变化幅度相对较小,2002年10月至2004年11月间的月均值低于云南地区的月均值。2005年云南地区的波速比整体偏高,平均值达1.74,高于多年均值,可能是2004年印尼8级大震后云南地区波速比的一种新变化。
From the 1998-2006 records of Yunnan Regional Digital Seismic Network,we selected the arrival time data of direct wave Pg and Sg that were observed by at least four stations and with clear phase(including the data of the far stations with arrival time difference of 20-25 s and near stations with arrival time difference less than 0.5 s).Then we calculated the VP/VS ratio of the Yunnan area and analyzed its regional distribution characteristics.The results show that the monthly average of VP/VS ratio is 1.685 in Yunnan during 1998-2006;the monthly average of VP/VS ratio in Southwest Yunnan is higher than that in Yunnan;the monthly average changes little in West Yunnan,and is lower than the average in Yunnan from Oct.2002 to Nov.2004.However,the VP/VS ratio in Yunnan has been high since 2005,about 1.685,higher than many years' average.We think it is a new change of VP/VS ratio in regional distribution after the 2004 Indonesia MS8.0 earthquake.
From the 1998-2006 records of Yunnan Regional Digital Seismic Network,we selected the arrival time data of direct wave Pg and Sg that were observed by at least four stations and with clear phase(including the data of the far stations with arrival time difference of 20-25 s and near stations with arrival time difference less than 0.5 s).Then we calculated the VP/VS ratio of the Yunnan area and analyzed its regional distribution characteristics.The results show that the monthly average of VP/VS ratio is 1.685 in Yunnan during 1998-2006;the monthly average of VP/VS ratio in Southwest Yunnan is higher than that in Yunnan;the monthly average changes little in West Yunnan,and is lower than the average in Yunnan from Oct.2002 to Nov.2004.However,the VP/VS ratio in Yunnan has been high since 2005,about 1.685,higher than many years' average.We think it is a new change of VP/VS ratio in regional distribution after the 2004 Indonesia MS8.0 earthquake.
引文
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阚荣举,韩源·1992·云南遮放至马龙地学断面(说明书)[M].北京:地震出版社·
梅世蓉·1993·中国地震预报概论[M].北京:地震出版社·
张学民,刁桂苓,束沛镒,等·2004·华北地区地下介质波速比值(VP/VS)研究[J].地震地质,26(2):305-317·
赵晋明,胡毅力,王彬,等·1996·在真三轴压缩条件下片麻岩破裂孕育过程中弹性波的特征变化[J].地震地质,8(3):277-281·
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