The problems of seismic impact of explosion on a tunnel are characterized. A methodology for determining the parameters in Sadovsky's formula for seismic wave displacement velocities based on the results of measurements at one point of the velocity time histories of seismic oscillations from subsequent short-term delayed explosions is proposed. The correlation between the parameters is established. The influence of errors in the determination of parameters on the calculation of seismically safe mass of the explosive charge is estimated.