呼和浩特—包头地区平均波速比分区特征研究
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摘要
内蒙古呼和浩特—包头地区地质构造复杂,历史上曾发生多次6级以上强地震。本文选取2001年以来该地区的ML≥1.0地震作为研究对象,根据地震空间分布和研究区域的台网布局,划分出4个子区域,分别计算了各个子区域的平均波速比,并对比分析其时间和空间变化;计算结果表明,各个子区域的平均波速比曲线随时间流逝的变化幅度相差较大,且呼和浩特地区的平均波速比明显低于其他3个地区的平均波速比,初步推断与呼和浩特地区的断裂构造分布及地下介质性质有关。震例研究结果显示,2003年托克托县ML4.6地震前震中区波速比变化过程为"下降—持续低值—回升发震"。
The Hohhot-Baotou area has the complex geological structure and had occurred many times of Ms≥6.0 earthquakes in history.The ML≥1.0 earthquakes in Hohhot-Baotou area are selected as the study object in this paper.According to the spatial distribution of earthquakes and the deployment of station network,this area is divided into 4 subareas.The average velocity ratio of each subarea is calculated and the analysis on the spatial-temporal variation is carried out.The results indicate that the difference in amplitude variation of average velocity ratio over time of each subarea is quite large,and the average velocity ratio of Hohhot area is significantly lower than that of other three subareas,from which deducing that this may be related to the distribution of fault structure and the nature of underground media.Studies on earthquake cases show that the change of velocity ratio(Vp/Vs) in the epicenter area is a process of "down-continuously low-up-earthquake occurrence" before the Tuoketuo ML4.6 earthquake in 2003.
The Hohhot-Baotou area has the complex geological structure and had occurred many times of Ms≥6.0 earthquakes in history.The ML≥1.0 earthquakes in Hohhot-Baotou area are selected as the study object in this paper.According to the spatial distribution of earthquakes and the deployment of station network,this area is divided into 4 subareas.The average velocity ratio of each subarea is calculated and the analysis on the spatial-temporal variation is carried out.The results indicate that the difference in amplitude variation of average velocity ratio over time of each subarea is quite large,and the average velocity ratio of Hohhot area is significantly lower than that of other three subareas,from which deducing that this may be related to the distribution of fault structure and the nature of underground media.Studies on earthquake cases show that the change of velocity ratio(Vp/Vs) in the epicenter area is a process of "down-continuously low-up-earthquake occurrence" before the Tuoketuo ML4.6 earthquake in 2003.
引文
[1]国家地震局预测预防司.测震学分析预报方法[M].北京:地震出版社,1997.
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[4]傅征祥,程燕.北京和张家口地区地壳平均波速比的联合测定[J].地震,1988(4):28-34.
[5]黎明晓,张晓东.应用多台法测定华北地区地壳的平均波速比[J].地震,2004,24(1):163-169.
[6]张学民,刁桂苓,柬沛镒,等.华北地区地下介质波速比值(Vp/Vs)研究[J].地震地质,2004,26(2):305-317.
[7]李永莉,毛慧玲,赵小艳,等.云南地区数字地震波波速比的区域特征[J].地震研究,2008,31(3):203-208.
[8]蔡静观,梅世蓉,张喜铃,等.从高波速比试论云南丽江7级地震的孕震模式[J].地震研究,1999,22(2):122-129.
[9]蔡静观.波速比计算中的不确定因素和在地震预报中的应用[J].地震研究,2000,23(1):51-56.
[2]冯德益.地震波速异常[M].北京:地震出版社,1981:186-200.
[3]嘉世旭,刘昌铨.邢台震源区波速比异常与地震的关系[J].地震学报,1996,39(supp):205-215.
[4]傅征祥,程燕.北京和张家口地区地壳平均波速比的联合测定[J].地震,1988(4):28-34.
[5]黎明晓,张晓东.应用多台法测定华北地区地壳的平均波速比[J].地震,2004,24(1):163-169.
[6]张学民,刁桂苓,柬沛镒,等.华北地区地下介质波速比值(Vp/Vs)研究[J].地震地质,2004,26(2):305-317.
[7]李永莉,毛慧玲,赵小艳,等.云南地区数字地震波波速比的区域特征[J].地震研究,2008,31(3):203-208.
[8]蔡静观,梅世蓉,张喜铃,等.从高波速比试论云南丽江7级地震的孕震模式[J].地震研究,1999,22(2):122-129.
[9]蔡静观.波速比计算中的不确定因素和在地震预报中的应用[J].地震研究,2000,23(1):51-56.
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