【摘要】 文中计算了华北地区最近20a来的8次M_S≥5.8地震前的森下指数。结果发现,在正常情况下,森下指数I_δ变化平稳,而到震前0.5～2a突然出现几倍于正常水平的上升变化。作者还将森下指数由空间域延伸到时间域,也取得了较好的效果。时间窗的长度、震级下限及网格尺度选取是影响森下指数计算结果的3个重要因素,只有三者组合得当才能获得好的效果。更多还原

【Abstract】 In this paper, Morishita index before 8 earthquakes (Ms≥5.8)in North China in recent 20 years has been calculated, the result shows that Morishita index Is varies steadily in normal condition, but suddenly appears several times as rising as normal variation in 0.5 - 2 years before earthquake occurrence. Morishita index is extended to time domain from spatial domain by authors, and its effect is better. Dimension of time window, lower limit of magnitude and grid dimension are three important factors to influence the result of Morishita index. Only when the three factors properly combined, can the relatively good effect can be obtained.更多还原