唐山大震前的地震空区和围空地震的机理

A DOUGHNUT-SHAPED PATTERN OF SEISMIC ACTIVITY AND ITS FORMATIVE PROCESS PRECEDING THE TANG- SHAN EARTHQUAKE OF 1976

  • 摘要: 本文通过分析区域小震活动的变异,指出:1)唐山大震前不同震级下限的围空图象,实际上是唐山附近的地震平静和外围三支小震条带活动,二者合成的结果;2)空区边缘的应力集中和地震活动增强,主要是断裂带活动的结果.最后用强度和应力分布不均匀的断层模式讨论了围空图象形成的力学过程.

     

    Abstract: The spatial-temporal variation of seismicity in the wide region surrounding the epicentre of the 1976 Tangshan earthquake (Ms=7.8) was examined. It has been pointed out that the pattern described as a seismicity gap or a doughnut-shaped pattern preceding the main shock is practically a partial manifestation for the whole pattern composed of seismically quiet epicentral area and three seismicity bands in the surrounding region, that the stress concentration toward the margin of the quiet area and the increase of seismicity are caused by the movement on the fractured zone. Finally, the mechanical process of the formation of the seismic pattern is explained by using the model of inhomogenuity of intensity and stress distribution along the fault zone.

     

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