In summer 2018 the energy company St1 carried out its first stimulation of deep geothermal wells in Otaniemi, Espoo, in the Helsinki metropolitan area, southern Finland. The Institute of Seismology of University of Helsinki (ISUH) monitored the induced seismicity during the stimulation, and also months before and after it. In the second half of 2022 ISUH consulted the Australian company Institute of Mine Seismology (IMS, https://www.imseismology.org) for providing seismic location and time data based on ISUH waveform data, and the IMS algorithm that is based on machine learning (doi: 10.1785/0220210068). The IMS location and time data were later transferred to formats used by ISUH. The resulting dataset consists of seismic waveforms of 483 induced earthquakes that occurred between 5 June 2018 to 26 July 2018, with local magnitudes between -0.7 and 2.0. Seismic data derive from stations of the Finnish National Seismic Network (doi: 10.14470/UR044600) the temporary HEL broadband network, the temporary borehole network of St1 (doi: 10.1785/0220190253), and a pool of lightweight mobile seismic instruments operated by ISUH (GIPP data cubes, doi: 10.5880/GIPP.201802.1, ). The deployment is described in Hillers et al., 2020, The 2018 Geothermal Reservoir Stimulation in Espoo/Helsinki, Southern Finland: Seismic Network Anatomy and Data Features, doi:10.1785/0220190253. Event data, event metadata, and station metadata are provided in distinct directories. For event data, each event is assigned a subdirectory. Data formats follow generally accepted seismological standards. Due to an unfortunate miscommunication, the IMS amplitude readings in this data product need to be halved in order to be compatible with the ISUH 2018 dataset. This also has the effect of reducing the local magnitude values reported herein by ~0.25 units.

2023