滇西地区中强地震前单台波速比的变化特征
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摘要
本文应用地震波的运动学特征,以滇西腾冲台、洱源台为例,研究了滇西地区1982—1990年近十次中强震在地震前的波速变化,对提取该地区孕震的前兆信息作了初步的探讨。文中给出并讨论了这些中强震前的单台波速比异常的共同特征,以及单台波速比变化的时间进程和波速比异常的平面图象,得出:(1)单台波速比的异常幅度一般在0.04—0.11之间;(2)异常时间与震级大小有关;(3)中强地震多发生在波速比异常区的边缘。 同时,对1988年11月6日耿马—澜沧7.6级、7.2级地震前腾冲台波速比异常也作了分析,结果为:震前波速比下降幅度超过历年最低值,异常时间亦持续了半年多,这些结果为我们进一步探索大地震的预报途径提供了定性的依据。
In this paper, by using the kinematic feature of seismic wave and taking Tengchong seismic station and Eryuan seismic station as examples, the variation of seismic wave velocity is studied before nearly 10 moderately strong earthquakes in the western Yunnan between 1982 and 1990, and extraction of precursory information of earthquake preparation in this region is preliminary discussed. The general features of the ratio of seismic wave velocities in single seismic station before these moderately strong earthquakes, and the variation cause of VP / Vs ratio with time and the anomalous plane patterns of VP / Vs ratio in single station are shown and discussed, the results are : (1) The anomalous ranges of the VP/ Vs ratio are usually between 0.04 and 0.11. (2) The anomalous time is related to the magnitude. (3) The moderately strong earthquakes are usually occurred at the edge of the region with the VP / Vs ratio anomaly. Meanwhile the anomalous ratio of wave velocities for Tengchong seismic station before M = 7.6 and M = 7.2 earthquakes in Gengma and Lancang on Nov. 6 1988 are also analyzed. The results show that the dropping range of the ratio exceeds the lowest valuse over the years. The results provide us a qualitative basis for exploring a new avenus to predict strong earthquake.
In this paper, by using the kinematic feature of seismic wave and taking Tengchong seismic station and Eryuan seismic station as examples, the variation of seismic wave velocity is studied before nearly 10 moderately strong earthquakes in the western Yunnan between 1982 and 1990, and extraction of precursory information of earthquake preparation in this region is preliminary discussed. The general features of the ratio of seismic wave velocities in single seismic station before these moderately strong earthquakes, and the variation cause of VP / Vs ratio with time and the anomalous plane patterns of VP / Vs ratio in single station are shown and discussed, the results are : (1) The anomalous ranges of the VP/ Vs ratio are usually between 0.04 and 0.11. (2) The anomalous time is related to the magnitude. (3) The moderately strong earthquakes are usually occurred at the edge of the region with the VP / Vs ratio anomaly. Meanwhile the anomalous ratio of wave velocities for Tengchong seismic station before M = 7.6 and M = 7.2 earthquakes in Gengma and Lancang on Nov. 6 1988 are also analyzed. The results show that the dropping range of the ratio exceeds the lowest valuse over the years. The results provide us a qualitative basis for exploring a new avenus to predict strong earthquake.
引文
(1) 冯德益等,我国西部地区一些强震及中强震前后波速比异常的初步研究(一)--波速比异常,地球物理学报,19,3,1976。
(2) 冯德益等,我国西部地区一些强震及中强震前后波速比异常的初步研究(二)--波速比异常区及其特性,地球物理学报,20,2,1977。
(3) 董颂声等,根据波速比变化作出中期地震预报的一个实例,地震学报,3,2,1981。
(4) 王炜等,安徽省及邻区地震预报方案的研究,地震,4,1989。
(5) 许绍燮,陆远忠等编著,地震预报方法实用化研究文集,地震学专辑,1989。
(6) 庄昆元等,利用专家系不精确推理方法确定未来地震危险区,中国地震,6,2,1990。
(2) 冯德益等,我国西部地区一些强震及中强震前后波速比异常的初步研究(二)--波速比异常区及其特性,地球物理学报,20,2,1977。
(3) 董颂声等,根据波速比变化作出中期地震预报的一个实例,地震学报,3,2,1981。
(4) 王炜等,安徽省及邻区地震预报方案的研究,地震,4,1989。
(5) 许绍燮,陆远忠等编著,地震预报方法实用化研究文集,地震学专辑,1989。
(6) 庄昆元等,利用专家系不精确推理方法确定未来地震危险区,中国地震,6,2,1990。
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