我国西部地区一些强震及中强震前后波速异常的初步研究（一）——波速比异常

本文对近年来我国西部地区发生的某些强震及中强震（M_S>5.0）的波速比异常作了一些初步探讨.文中给出并讨论了这些地震的波速比异常的一些共同特征,即随时间变化的曲线形态、异常特征量（异常持续时间与异常幅度）和异常的统计分布特征.此外还讨论了波速比异常的特性与地震序列类型、震源深度及震源机制的关系,探索了波速比异常与波速异常间的关系.最后还指出了地震活动性与波速比异常的某种对应关系,并作了简要的讨论.

PRELIMINARY STUDY OF THE VELOCITY ANOMALIES OF SEISMIC WAVES BEFORE AND AFTER SOME STRONG AND MODERATE EARTHQUAKES IN WESTERN CHINA （I）——THE VELOCITY RATIO ANOMALIES

In this paper are discussed the preliminary results of the velocity ratio ano-malies of seismic waves before and after some strong and moderate earthquakes（M_s > 5.0） occurred in Western China in recent years. Some general characteristicsof the V_P/V_S anomalies are discussed, namely, the form of the curves of the V_P/V_Svariation with time, certain characteristic values （the duration and the amplitude）of the V_P/V_S anomalies and their statistical distribution. Besides, the relations be-tween such characteristics of the V_P/V_S anomalies and the types of earthquake se-quences, the focal depths and the mechanisms of earthquakes are also discussed. Asearch is made for the correlations between the V_P/V_S anomalies and individualV_P, V_S anomalies. And finally, it is pointed out briefly the relation between theseismic activity of a region and the V_P/V_S anomaly.