Abstract: Measurements of magnetotelluric sounding indicate two highly conductive layers in the crust and upper mantle in the Tangshan area.They lie at a depth of about 20km and 100km,respectively.And they are found deep at southern section and shallow at northern section.The results show that both of the Tangshan earthquake and the Ninghe one occurred along a variable depth-gradient zone for the two layers,with their focal depths no more than those for highly conductive layers in the crust.It has been found in the south of the Tangshan area that a highly conductive layer may be conjectured to be at a depth of 45km,an intermediate one within upper mantle.

摘要： 大地电磁测深结果表明,唐山地区深部电性中存在壳内高导层和上地幔高导层,其分别埋深为20公里和100公里左右,均显示为南浅北深。资料对比表明唐山、宁河地震都发生在两个高导层埋深变化梯度带上,其震源深度都不超过壳内高导层的埋深。此外,在该区南部发现埋深约45公里高导层,我们认为有可能为上地幔中间高导层。