Assessment of the Seismic Impact from Grouped Quarry Blast Using Standard Seismic Survey Equipment

The study presents a methodology for using standard seismic survey equipment for assessment of the impact of grouped blasts from quarries. Example from а limestone quarry situated at more than 1.5 km from the thermal spring “Merichlery” in South Bulgaria is discussed. After the two strong earthquakes from 14.04.1928 (М=6.8, Chirpan Earthquake) and from 18.04.1928 (М=7.0, Popovitsa Earthquake) the water from the spring disappeared. A survey was executed for assessing the impact of the blasts on the houses and the discharge of the mineral water from the exploitation borehole. The results are compared to the national and international criteria for the safety limits of accelerations and velocities of the ground in relation to the seismic frequencies. Reference to the maximum expected ground accelerations from earthquakes on the concerned site is also presented. The maximum vertical acceleration from the quarry blasts was calculated to be between 32.81 and 57.62 cm/s2, and the horizontal one – between 37.51 and 233.95 cm/s2 (single high frequency picks). These results indicate that no one record overpasses the normative level of accelerations from earthquakes for the area - 0.27 g (265 cm/s2). In average the recorded accelerations were 2.5 times lower than the normative.