Volumetric changes of rock massif preceding mining seismic events

•We observed the volumetric changes in the rock mass using new measurement method.•We measured the changes in oil pressure in the probe container placed in the borehole.•We separated symptoms of mining-induced seismicity.•Transient pressure changes often precede the occurrence of seismic events.•Volumetric method may be useful in determining potential seismic hazards.