In the Otaniemi geothermal project of St1, geophones installed in the bedrock of the Helsinki Metropolitan area discovered in the night 14.4.2020 1.67 magnitude micro-earthquake in the deep bedrock.
The effects of this magnitude have been detectable at ground level in the surrounding areas for example in the form of sound and sound waves can also resonate eg. in windows and structures, but do not cause a risk to humans or damage structures.
The Institute of Seismology has monitored 1.0 magnitude micro-event. The differences in the measurement result is due to differences in measurement methods and equipment. The St1 equipment is tuned to detect earth movements as accurately as possible.
The ongoing logging and measurement activities in the heat well that was completed in March, required a momentary drilling fluid pressure pulse. This pressure pulse caused a microseismic event, similar to momentary stimulation. This was measured inline with the seismic monitoring system.
St1 implements the seismic monitoring according to the measures required by the authorities. We communicate all micro-events exceeding 1.2 magnitudes at our project website.
Geophone measurement results as well as up to date information can be monitored online www.st1.eu/geothermal-heat
All seismic events in Finland and adjacent areas can be monitored at the Institute of Seismology www.seismo.helsinki.fi/bulletin/list/alert/current_map.html