[en] Excavation of the underground characterisation facility (the ONKALO) started in 2004. Before that, in February 2002, Posiva Oy established a local seismic network of six stations on the island of Olkiluoto. After that the number of seismic stations has increased gradually. In 2010 Posiva's permanent seismic network consists of 15 seismic stations and 20 triaxial sensors. The purpose of the microearthquake measurements at Olkiluoto is to improve understanding of the structure, behaviour and long term stability of the bedrock. The investigation area includes two target areas. The larger target area, called seismic semiregional area, covers the Olkiluoto Island and its surroundings. The purpose is to monitor explosions and tectonic earthquakes in regional scale inside that area. The smaller target area is called the seismic ONKALO block, which is a 2 km *2 km *2 km cube surrounding the ONKALO. It is assumed that all the expected excavation induced events occur within this volume. At the moment the seismic ONKALO block includes ten seismic stations. An additional task of monitoring is related to safeguarding of the ONKALO. This report gives the results of microseismic monitoring during 2010. In March 2010, the seismic network was upgraded by a new triaxial borehole seismometer in order to improve the sensitivity and the depth resolution inside the ONKALO block. The sensor is the second one inside the ONKALO. New PC for data processing and analysis with the new version of Linux operating system was installed. Also all software packages for data processing and analysis and for visualization were upgraded. The network has operated continuously in 2010. Altogether 1089 events have been located in the Olkiluoto area, in reported time period. Most of them (943) are explosions occurred inside the seismic semi-regional area and especially inside the seismic ONKALO block (895 events). The magnitudes of the observed explosions inside the semi-regional area range from M_L = -1.8 to M_L = 1.5 (M_L = magnitude in local Richter's scale). Most of them are explosions. Three of the events are classified as induced microearthquakes. Three injection induced microearthquakes (M_L = -1.6, M_L = -2.1 and M_L= -3.0) occurred on 16.12.2010. They can be associated with the structural orientation of the upper contact of the pegmatitic granite unit PRG44 or veined gneiss. The events locate about 50 - 80 meters above the closest excavated part of the ONKALO. Estimated peak slip values of the earthquakes are less than five μ m and the source radiuses less than five meters. According to seismic monitoring the rock mass surrounding the ONKALO has been stable in 2010. Indications of illegal or inappropriate works, which would have influence on the safety of the ONKALO, have not been found. (orig.)