强震前的重力变化特征

FEATURES OF GRAVITY VARIATIONS BEFORE STRONG EARTHQUAKES

地震前,地壳变形引起地球密度重新分布,从而使地球重力场发生某些特征变化。本文对1990年7月菲律宾8级、台湾6.1级两个强震前后的广州重力资料进行了调和分析及高、低频滤波等处理,并对提取出的重力前兆进行了可信度检验。结果表明强震前广州地区的重力变化具有O_1等主波潮汐因子波形畸变,量值下降至最低值然后在回升阶段发震的前兆异常特征。非潮汐重力变化在临震前3天开始出现明显的高频脉冲式异常信息,作者认为这是一种可信的具有清晰物理意义的地震短临前兆。

Before earthquake occurrence, the crustal deformation causes redistribution of the earth density, so there occur some characteristic changes in the earth gravity field. This paper harmonically analyzed Guangzhou gravity data before and after both Philipine M 8 and Taiwan M 6.1 earthquakes in July 1990 and processed the high and low frequency filtrering, and also examined the reliability of the extracted gravity precursor. Results show that before strong earthquakes, the gravity variation in Guangzhou region displays waveform distorsion. of O1 main-wave tidal- factor, the magnitude fall down to the lowest value, then the earthquake occurred while the value rose. Three days before earthquakes the nontidal gravity variation began having obvious high-frequency pulse anomaly information, authors here consider that this is a reliable short-impending earthquake precursor with clear physical meaning.