中强震前的小震Q值变化特征

CHARACTERISTICS OF SMALL-EVENT Q VALUE CHANGES BEFORE MODERATE-STRONG EARTHQUAKES

本文利用振幅衰减系数和卓越频率衰减系数计算中强震前的小震Q值。通过对不同地区的典型震例的分析,发现在中强震发生前,小震Q值持续增大,增加的幅度是正常值的数倍,但异常幅度与震级无明显关系,而异常时间可能与主震震级有关。

Using the attenuation coefficients of amplitude and predominant frequency, the small-event Q value before moderate-strong events has been calculated. Summing up the typical earthquakes occurred in different regions, it can be seen that the small-event Q value continuous increases before the moderate-strong events take place, the amplitude of Q value increase is several times larger than that of the normal value. Never-theless, the amplitude of the anomalies is irrelevant to the magnitude of the subsequent earthquake, yet the duration of the anomalies is related to the magnitude of the subsequent event. Larger earthquakes trend to be preceded by longer duration of anomalies.