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Induced seismicity is one of the main factors that reduces societal acceptance of deep geothermal energy exploitation activities, and felt earthquakes are the main reason for closure of geothermal projects. Implementing innovative tools for real-time monitoring and forecasting of induced seismicity was one of the aims of the recently completed COSEISMIQ project. Within this project, a temporary seismic network was deployed in the Hengill geothermal region in Iceland, the location of the nation's two largest geothermal power plants. In this paper, we release raw continuous seismic waveforms and seismicity catalogues collected and prepared during this project. This dataset is particularly valuable since a very dense network was deployed in a seismically active region where thousand of earthquakes occur every year. For this reason, the collected dataset can be used across a broad range of research topics in seismology ranging from the development and testing of new data analysis methods to induced seismicity and seismotectonics studies., Scientific Data, 9, ISSN:2052-4463

The increased interest in subsurface development (e.g., unconventional hydrocarbon, engineered geothermal systems (EGSs), waste disposal) and the associated (triggered or induced) seismicity calls for a better understanding of the hydro-seismo-mechanical coupling in fractured rock masses. Being able to bridge the knowledge gap between laboratory and reservoir scales, controllable mesoscale in situ experiments are deemed indispensable. In an effort to access and instrument rock masses of hectometer size, the Bedretto Underground Laboratory for Geosciences and Geoenergies ("BedrettoLab") was established in 2018 in the existing Bedretto Tunnel (Ticino, Switzerland), with an average overburden of 1000 m. In this paper, we introduce the BedrettoLab, its general setting and current status. Combined geological, geomechanical and geophysical methods were employed in a hectometer-scale rock mass explored by several boreholes to characterize the in situ conditions and internal structures of the rock volume. The rock volume features three distinct units, with the middle fault zone sandwiched by two relatively intact units. The middle fault zone unit appears to be a representative feature of the site, as similar structures repeat every several hundreds of meters along the tunnel. The lithological variations across the characterization boreholes manifest the complexity and heterogeneity of the rock volume and are accompanied by compartmentalized hydrostructures and significant stress rotations. With this complexity, the characterized rock volume is considered characteristic of the heterogeneity that is typically encountered in subsurface exploration and development. The BedrettoLab can adequately serve as a test-bed that allows for in-depth study of the hydro-seismo-mechanical response of fractured crystalline rock masses., Solid Earth, 13 (2), ISSN:1869-9510, ISSN:1869-9529

During 2014, 817 earthquakes and 180 quarry blasts were detected and located in the region under consideration. An additional 160 earthquakes with ML ≤ 1.0 were located using supplementary analysis techniques. The number of located earthquakes in 2014 was the largest since the installation of a seismic network in Switzerland in 1975. This unusually large number is mainly due to the occurrence of two vigorous earthquake sequences, and the local reduction of the earthquake detection thresholds of the Swiss seismic network. With a total of 22 earthquakes of ML ≥ 2.5, the seismic activity of larger and potentially felt events was close to the average of 23 earthquakes over the previous 39 years. The most noteworthy seismicity was the earthquake sequence near Diemtigen, west of Lake Thun, where more than 270 events were located between April and December. High-precision hypocenter relocation was applied to image the spatio-temporal evolution of this seismicity. The sequence culminated in an M L 3.2 event in October, which was felt in the region of Lake Thun and Bern. Other cases of earthquakes felt by the public include earthquakes in the region of Biel (ML 3.2), in Vallorcine (ML 3.2), and in Stalden (ML 3.0). Finally, a small but unusually deep earthquake was recorded beneath the Jura Mountains. Focal depth, apparent velocities, as well as waveform characteristics of this earthquake are consistent with a source in the uppermost mantle. This earthquake is the first reliable record of a sub-Moho event ever observed in Switzerland., Swiss Journal of Geosciences, 108 (2-3), ISSN:1661-8734, ISSN:1661-8726