摘要
本文论述了１９９６年２月３日丽江７０级地震前洱源、腾冲两个地震台的多项地震波运动学和动力学异常及滇西北多台波速比异常的特征，探讨了其时空演化的动态变化过程。得出：在时间进程上，多项地震波突变特征均在震前一年左右的时间出现。其中，波速比在大震前的单点突变异常幅度为中强震的５倍之多；振幅比突变异常幅度约为中强震的３—５倍；尾波持续时间比则是在震前一年左右出现持续性的低值，时间尺度约为中强震异常时间的３倍以上。同时，在空间演化图像的分析也表明，呈条带分布的波速比异常区在震前１—３年出现走向上的转折，而异常条带转折的交汇区域即为未来大震的震中。因而指出了地震波在某一时段所呈现出的大幅度突变或波速比异常区发生的走向上转折的交汇区，可视为大震的中短期震兆信息。此外，突变点的空间位置对未来大震具有一定的指示意义。
The multiple anomalies of seismic wave in kinematics and dynamics observed at Eryuan and Tengchong stations, Vp/Vs ratio anomalies recorded at numerous stations in northwest Yunnan and their dynamic evolution process in time-space before the M 7 0 Lijiang earthquake on Feb 3, 1996 are discussed in this paper It is found that all the multiple mutation characters of seismic wave appeared about one year before the event; of the mutation characters the abrupt anomaly scale of Vp/Vs ratio at sigle point before the large event was 5 times of the scale of that before moderate-strong event; the abrupt anomaly scale of amplitude ratio before the large event was about 3-5 times of the scale of that before moderate strong event; the continuous time ratio of coda wave remained in low value of anomaly for about one year before the event and the time scale was about 3 times larger than that before moderate-strong event At same time, the analysis of spatial image evolution shows that a turn in the strike of anomalous area of velocity ratio in strip distribution appeared 1-3 years before the event, and the intersection area of anomalous strips with the turns is the epicenter of future large event Therefore, the abrupt in large scale of seismic wave in some time interval or the intersection area of velocity ratio anomalies with turns in strikes may be a precursor information of medium-short term before great event And also, the spatial location of mutation point has some meaning to futrue great earthquake, but in does not mean the epicenter of the great earthquake
出处
《地震研究》
CSCD
北大核心
1997年第1期108-116,共9页
Journal of Seismological Research
关键词
地震前兆
地震波
时空演化
Seismic wave, mutation, M 7 0 Lijiang earthquake, Yunnan
