Origin of mass faulting during seismic activation in the Central Kuznetsk basin

In 2005, the low magnitude shallow hypocenter swarm seismic activation occurred in the central part of Kuznetsk Depression. It continues until today. The main objects of implemented field works were numerous ruptures appearing on the surface in the vicinity of the town of Polysayevo during the activation period. In addition to chaotically distributed subsidences, slumps, and cracks related to surface saggings above worked mine fields, linear fractures of the Earth’s surface were found. These fractures form regular structural parageneses and comprise a relatively large system of 7.6 km total length. Regular structural parageneses and displacements along the faults of up to 10 cm in amplitude allow us to consider them as surface tectonic fractures. The depth of earthquake hypocenters, based on instrumental data, reaches 5 km; i.e., quakes occur significantly deeper than mine fields, which are located down to a 500 m depth. It is possible to suppose that the summarized impulse effect of seismic activation had led to formation of seismotectonic deformations in the zone of an already existing fault. The difference of the described fractures from typically seismotectonic ruptures is their gradual, slow formation. Approximate time of the start of formation for the studied fractures is several years ago, with continuous renewal up to the present. Another difference of the surface fractures is their remote positions at the distance of 1–2 km west of the epicentral area of the earthquakes swarm.