张之立. 1985: 唐山地震热力源的研究. 地震学报, 7(1): 45-56.
引用本文: 张之立. 1985: 唐山地震热力源的研究. 地震学报, 7(1): 45-56.
1985: INVESTIGATION ON THE THERMAL FORCE SOURCES OF 1976 TANGSHAN EARTHQUAKE. Acta Seismologica Sinica, 7(1): 45-56.
Citation: 1985: INVESTIGATION ON THE THERMAL FORCE SOURCES OF 1976 TANGSHAN EARTHQUAKE. Acta Seismologica Sinica, 7(1): 45-56.

唐山地震热力源的研究

INVESTIGATION ON THE THERMAL FORCE SOURCES OF 1976 TANGSHAN EARTHQUAKE

  • 摘要: 本文从应力场角度分析了1976年唐山地震发生的可能力源。震前唐山地区除受有太平洋板块和印度板块的作用外,主要受有附近的热力源的作用。以渤中为中心的下辽河—渤中—黄骅上地幔隆起的高温区和沧东断裂水平温度梯度带的存在,使唐山地区位于热应力集中区。本文根据已有的观测结果,提出了将温度变化区简化为圆形、狭长矩形和椭圆形等三个力学模式,分别求得它们的解析解,并计算了它们的热应力场。结果表明:在增温区以内,正应力都是压应力,剪应力很小。在增温区以外,法向应力为压应力,周向应力为张应力,水平剪应力较大,但各个应力分量随着距离增加而衰减,只在增温区的边缘地带达到最大值,其数值有几百巴的数量级。唐山恰好位于该增温区的边缘地带,表明热力源是促使唐山地震发生的重要原因。 除唐山地震外,华北地区近年发生的几个大地震如邢台、河间、渤海、海城地震,以及1983年发生的菏泽地震,均位于热应力的高值地带,这些地震的孕育和发生显然也与热力源的作用有关。

     

    Abstract: In this paper, the possible force sources of the 1976 Tangshan earthquake are discussed from the view point of stress field. The Tangshan area was affected obviously by the neighbouring geothermal sources besides the action of the Pacific Ocean and Indian Plates before the earthquake. The rising temperature zone of upper mantle uplift of Xialiaohe—Bohai—Huanghua centred on the Bohai Bay center and the horizontal temperature gradient zone of Cangdong Fault made the Tangshan area concentrated with geothermal stresses. Based on the observation data, three mechanical models, simplified the temperature variation area as a circle, a long narrow rectangle and an ellipse respectively, are presented in order to evaluate the magnitude of geothermal stresses. The analytical solutions of the geothermal stress field of above the models are calculated. The results show that the normal stresses are all compressive stresses and shear stress is small within the temperature rising area; the radial stress is compressive stress but the hoop stress is tensile stress. All the stresses attenuate outside the temperature rising area. The hoop stress and horizontal shear stress are maximum on the edge of the temperature rising area and their value may reach several handreds bars. Therefore, the geothermal stresses resulting from the thermal sources of the Xialiaohe—Bohai—Huanghua uplift and Cangdoug Fault zones may be an important force sources for the Tangshan earthquake.Besides the Tangshan earthquake, several present strong earthquakes such as the Xingtai, Hejian, Bohai, Haicheng, and Heze earthquakes occurred in north China were also located on the high value zones of the geothermal stresses. Their occurrences may all be connected with the above geothermal force sources.

     

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