An extension-dominant 9-km-long ground failure along a buried geological fault on the eastern Beijing Plain, China

Abstract

In the northern Beijing Plain (BPN), ground failures associated with land subsidence have occurred and rapidly progressed, damaging hundreds of buildings and roads in recent years. In 2016, an 8.7-km-long ground failure, named the Songzhuang (SZ) ground failure, was discovered in the eastern part of the Beijing Plain. Geological surveys, mapping, creep measurements, trenching, drilling, and geophysical exploration indicate that the SZ ground failure has geometric structural features and surface deformation that differ from those of other ground failures in the BPN: First, the SZ ground failure consists of one main fissure and many secondary fissures. Second, the SZ failure shows tensile deformation with negligible vertical dislocation. Third, in the profile, the SZ ground failure shows extensional cracks with limited extension depths that close gradually with depth. Based on the relationships between ground failures and influencing factors, including a pre-existing fault, earthquakes, and groundwater pumping, we conclude that this failure took shape after the earthquake, and was enlarged under the action of groundwater pumping. The pre-existing fault, which is a subsidiary fault of the northern section of the Nanyuan-Tongxian (NTN) fault, determined the area in which the SZ ground failure first formed.