【摘要】 营口地震台位于海城大地震震源区域内。大地震之前两年九个月,营口台P波残差已持续升高了一年四个月。升高幅度在0.34—0.73秒间。在升高的背景上,似乎存在两个高峰,一个低谷。 此种变化表明,大地震之前台站附近地壳—上地幔内曾出现P波速度下降的区域。看来,这个区域是不稳定的,相应于P波残差的变化,有两次伸长和一次收缩。这可能是地内深处岩浆侵入活动的结果;由此而导致大地震的发生。更多还原

【Abstract】 The Seismograph Station of Yinkou (营口) is located in the source region of Haicheng Earthquake. During two years and nine months before the shock, increase of P wave residuals at this station lasted for one year and four months. The amplitude of the increase is between 0.34 sec. and 0.73 sec. It seems that there are two highs and one low. These variations show that a zone of decreased P wave velocity may be found in the crust and upper mantle beneath the station. It appears that this zone is unstable, twice under extension and once contraction. It may be due to the variation in this zone caused by the effect of magmatic activities at great depth, and resulting in the occurrence of the large earthquake.更多还原