Past projects

Earthquake activity in the vicinity of the borehole has been monitored by a seismic network since the start of the project. The indications from the amassed data are that seismic activity in the stimulated area has more or less continually decreased since the project ended in 2006. Roughly a year after the closure of the borehole in April 2011, seismic activity in the immediate vicinity of the borehole markedly increased again. This increase has been particularly noticeable since the second half of 2016 and typically consisted of swarms of microearthquakes, with phases of increased activity over a number of weeks being followed by quieter periods. So far, none of these earthquakes were felt by the public.

Apart from the seismic activity, in recent months the spatial distribution of the quakes has also shifted. The latest earthquakes occurred at the southern and northern edges of the previously affected area, suggesting that the artificially induced fractures are spreading. In addition, measurements show that the hydraulic pressure in the reservoir (pore pressure) has steadily increased since the borehole was closed. A detailed analysis of the seismic data and modelling of the relationship between earthquakes and increasing pore pressure have shown that even modest pressure increases in the reservoir can significantly increase seismicity.

On 28 March 2017, in consultation with Basel Industrielle Werke (IWB) the Department of Health of the Canton of Basel decided to re-open the borehole created in Basel as part of the "Deep Heat Mining" geothermal power project in 2006. An extensive scientific study by the Swiss Seismological Service (SED) at the ETH Zurich revealed that the increased earthquake activity will most probably subside again in the long term if the borehole is opened.

Right from the start of the project, the Swiss Seismological Service (SED) has been responsible for independently monitoring the seismic stimulation process. Recorded quakes have constantly been registered by a purpose-expanded seismic network, their epicentre was located by the SED and the results were published as a database and on maps on the project website. When a recorded quake has a local magnitude of 2.0 or more, the SED also informs the relevant authorities. In addition, the SED also provided the authorities of the Canton of Basel-Stadt on the implementation of the SERIANEX study [1] with expert advice on the earthquake risk of the Deep Heat Mining project. Since May 2012, the canton has commissioned the SED to take over the seismic monitoring of the immediate vicinity of the borehole in Basel from Geopower Basel. Furthermore, in March 2017 the SED drafted an analysis of induced earthquakes following the discontinuation of the geothermal energy project in Basel.

Click here for more information on the SED's role in monitoring geothermal energy projects.

_{[1] Baisch Stefan, Carbon David, Dannwolf Uwe, Delacou Bastien, Devaux Mylène, Dunand François, Jung Reinhard, Koller Martin, Martin Christophe, S. M., & Secanell Ramon, V. R. (2009). Deep Heat Mining Basel Seismic Risk Analysis SERIANEX.}