Characteristics and main causes of earth fissures in northeastern Beijing Plain, China

Earth fissures (EF) form in the northeastern Beijing Plain, causing horizontal and vertical displacements of the ground surface and damaging hundreds of buildings and roads. In addition, since 2009, an unprecedented number of cracks with vertical offsets have occurred in the Beijing Capital International Airport (BCIA), which is the busiest airport in China, causing serious financial losses and increasing the risk of air travel. The EF were divided into three groups, including EF1, EF2, and EF3, based on their distribution and deformation patterns. In general, the EF1 and EF2 fissures formed along segments of the NE-SW trending regional normal faults and have large vertical offsets but small widths. The deformation patterns, trenches and geophysical prospecting profiles, demonstrate that the EF1 and EF2 fissures propagated from the preexisting faults. In contrast, the EF3 fissures formed in a disorganized pattern above the paleochannels of the Chaobai River with short lengths and negligible vertical offsets. The monitoring data for the EF1 fissures indicates that the formation and deformation of the EF in the northeastern Beijing Plain were induced by groundwater pumping. The formation processes of the EF1, EF2, and EF3 fissures are classified into two categories: (1) on the existence of preexisting normal faults and (2) on the existence of paleochannels. Two hypothetical conceptual models are presented to illustrate the formation processes.