辽东地区和海城地震区的地热观测
GEOTHERMAL OBSERVATION IN EAST LIAONING AND THE HAICHENG SEISMIC AREA
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摘要: 1980年至1984年间,在辽东地区和海城地震区,我们利用地质、冶金和化工部门的一批勘探钻孔,观测了这些井孔不同深度的温度,由此获得它们沿深度方向的温度梯度.同时,从这些观测孔取得岩样,在实验室中测定它们的热导率,从而得到每个钻孔的热流值.我们一共得到23口钻孔的热流数据,其中包括海城地震区的两个热流观测孔.这些热流值可粗略地给出海城地震区和辽东地区的热结构.结果表明,平行郯庐断裂的辽阳——熊岳北东条带具有相对高的热流值,平均热流为8.2910-2J/m2s(2.0cal/cm2s).这个条带恰好是下辽河盆地和辽东山地的交界,它与重力异常梯度带显示的北东向上地幔隆起带一致.海城地震区的平均热流值达9.2210-2J/m2s(2.2 cal/cm2s),又是高热流值条带上热流最高的区域.比较海城地震区已知的其它地球物理资料后,给出了该地区地球物理资料的综合解释剖面.我们推测,海城地震区下,地壳中的低速层是由于上地幔物质的大规模侵入产生的.高温和低速意味着该层具有塑性力学性质.海城地震震源区恰好位于这样一个塑性状态的介质层上部.这个结果对于研究海城地震和其它板内地震的形成过程无疑是有意义的.我们试图强调,对于地震研究而言,热流观测是地球物理观测中不可缺少的组成部分.地热资料Abstract: We have obtained altogether heat flux data of 23 drill holes including 2 observational holes of thermal flow in the Haicheng seismic area. These data show roughly thermal structure of crust in east Liaoning and the Haicheng seismic area. The results indicate that there is higher rate of heat flow in the north by east belt from Liaoyang to,Xiongyue, and the average thermal flux is 8.2910-2 J/m2s (2.0 HFU). Average thermal flux in the Haicheng seismic area is 9.2210-2J/m2s (2.2 HFU).Comparing with other known geophysical data of the Haicheng seismic area, we give a geophysical section of synthetic interpretation. We suppose the low-velocity layer in the lower crust of the Haicheng seismic area is a result of large-scale intrusion of upper mantle substance. High temperature and low seismic velocity mean that the layer has the nature of plastic mechanics. The focal region of the Haicheng earthquake is situated right in the upper part of that plastic layer. Obviously, this result is significant for studying the seismogenic process of the Haicheng earthquake and other intra-plate earthquakes.We venture to emphasize that the observation of heat flow is indispensible for earthquake study.