Abstract

With UK’s net-zero carbon emissions goal for 2050, geothermal energy has become a promising renewable energy source with its low carbon footprint. In 2020, it stood for 4.5% of UK’s renewable energy, and there are several geothermal projects planned for the near future. However, one of the risks associated with geothermal production is induced seismicity. Although small microseismic events are natural at geothermal sites, a few recent cases of larger earthquakes overseas have alarmed the public, caused damage, and paused or halted the energy development. Thus, as UK is developing its geothermal sites, it is important to analyse the first earthquakes available from each location to better understand how the regions respond to ground motions and how the earthquakes behave.

Using a local Raspberry Shakes seismic network, we examined the induced earthquakes from the United Downs geothermal site in Cornwall, UK, and found that the region experiences more high-frequency content than expected based on relevant models. We also concluded that low-cost Raspberry Shakes are a suitable alternative for preliminary seismic hazard analysis in regions lacking seismic networks. Additionally, we investigated the first induced earthquakes from the Helsinki, Finland, deep geothermal site to get a closer look at the rupture behaviour of the earthquakes, identifying clear rupture directivity and complex behaviour similar to larger, natural earthquakes.