In order to reduce the risk of induced seismicity related to underground mining, a number of preventive actions are applied in the form of passive and active prevention methods. The former are mainly of an organisational nature and their effectiveness is usually considered in the long term, while the active methods are mostly based on the detonation of explosives and are aimed to release the seismic energy accumulated in the rock mass. In this paper, modifications of the firing pattern aimed to concentrate the paraseismic vibrations while maintaining the appropriate excavation of the mining face has been verified on the basis of underground tests. The evaluation was based on fragmentation analysis. The obtained results confirmed, that the blasting pattern modifications related to the reducing of the face firing time do not cause significant differences in terms of the appropriate excavation of the mining face.