Abstract: Tectonic cave-in is straitforward defined as the cave-in of crustal layers associated with tectonic movement.This idea was first published about 20 years ago and explaining the phenomena of Tangshan earthquake with such viewpoint has a history of more than 10 years as well.The levelling measurements across the main fault of Tangshan earthquake suggest that,during 1970 Fengnan earthquake (M=4.7),large scale tensile failure may have occurred in the downthrown block.The long-term anomalous changes in water level and gravity which began later can be explained by assuming that ground water moved into the region of the tensile fractures in this period.

Key words: Tectonic cave-in, Tangshan earthquake, Long-term precursory anomalies

摘要： 构造塌陷,是指构造运动造成的地壳岩层塌陷。根据唐山地震前的跨地震主断裂的水准测量结果,可以认为,伴随1970年5月25日的丰南地震,在主断裂下降盘内出现了大规模的侧向张破裂。这以后出现的地下水位和重力等震前趋势异常,都可以用地下水向破裂区的迁移来解释。

关键词: 构造塌陷, 唐山地震, 地震趋势异常