[en] EDZ (Excavation Damaged Zone) is a damaged region in rock mass surrounding excavated rock spaces, e.g. tunnel or shaft profile. Damages and irreversible deformations are caused by fracture propagation and/or development of new fractures caused by excavation. The goal of this work was to support the micro seismic measurements made in ONKALO Project in the Olkiluoto area. Other objectives were to investigate the success of excavation, vibration conductivity of rock mass in the tunnel, and the magnitude of EDZ resulted in excavation. Research methods used in this work have been: investigation of the results from vibration monitoring, time history curves from vibration sensors, the initial excavation data (drilling- and charging registers), and reports from excavation contractor and experiences from previous studies performed in ONKALO. Based on the results and visual observation, excavation in ONKALO does not have an abnormal effect in the surrounding rock mass. Results indicate that EDZ surrounding the profile is approx. 0.5 meters. Because of the great amount of uncertainty factors, the cracking zone value can be considered as a rough estimate. Comparison with the results from Posiva Oy's micro seismic sensors indicates that data from Finnrock's sensors could not be compared with them coherently. As a result from the vibration conductivity it could be concluded that the rock mass between the sensors was, as a rule, quite solid. This would indicate a limited EDZ. Results of the performed measurements seem to be realistic. Results are congruent with theory and experiences previously gained from studies performed in ONKALO. (orig.)