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本文对四次大地震(大关、渤海、松潘、唐山)的基式仪资料进行分析,发现松潘地震前的长周期蠕动波并非孤立现象,渤海、唐山地震前也确实存在。其特征类似,周期20—80秒,幅度10°—10~2微米,能量相当于4—5级“慢地震”。蠕动以波的形式传播,波速为0.5—3.5公里/秒。但松潘地震前的蠕动波速为1.1—1.2公里/秒,而渤海与唐山前为2—3.5公里/秒。频谱随震中距发生变化,松潘与唐山的情况相反。蠕动源不是震中,而在震中附近。前兆提前量1—2天。1974年大关7.1级地震则未发现这种长周期波动,仅表现特殊脉动。
In this paper, the data of ground-based instruments of the four major earthquakes (Daguan, Bohai, Songpan and Tangshan) are analyzed. It is found that the long-period peristalsis wave before the Songpan earthquake was not isolated and existed before the Bohai Sea and Tangshan earthquakes. Its characteristics are similar, the period 20-80 seconds, the amplitude of 10 ° -10 ~ 2 microns, the energy equivalent to 4-5 “slow earthquakes.” Peristaltic waves spread in the form of wave velocity of 0.5-3.5 km / s. However, the wave velocity of peristalsis before Songpan earthquake was 1.1-1.2 km / s, while that of Bohai Sea and Tangshan was 2-3.5 km / s. Spectrum changes with the epicentral distance, Songpan and Tangshan the opposite situation. Peristaltic source is not epicenter, but near the epicenter. Precursory advance 1-2 days. The magnitude 7.1 earthquake of 1974 showed no such long-term fluctuations and showed only specific ripples.