Tectonic creeping ground fractures are common in the ground
fractures, and some regional ground fissures, which are
concentrated at home and abroad, generally have the background
of neotectonic activity. It is pointed out that under the action
of steady and slow tectonic stress, if the strain accumulation
reaches the critical value of rock formation fracture deformation,
the ground fissure may occur on the surface, and with the increase
of this stress, the ground crack will develop and expand gradually.
In a large area controlled by the same stress field, where ground
fissures are most likely to occur, it is the area where strain
accumulates, the rock is fragile and the active structure changes
violently, including the active fault zone, the active fold axis
and the turning point of active structure rising and falling,
and so on.
In the study of the ground fissures in Xi'an, it is generally
considered that the Fenwei graben is a typical neotectonic active
area in China. The concentrated occurrence of the ground fissure
in this area is obviously synchronized with the intensification
of the regional tectonic activity in time, and the distribution
of the ground fissures is obvious. Many aspects, such as the mode
of activity, obviously show uniform structural characteristics.
Many scholars have put forward the generalizable model of tectonic
mechanism of Xi'an ground fracture from different angles, among
which the most representative one is Zhang Jiaming's theory of
fault block tilting in 1990. It is believed that under the action
of NNW extensional stress to the region, Activities of Xi'an
extensional fault system with fault block tilting as its main
active form constitutes the essence of the formation
and development of the ground fissures in Xi'an.