Research portal

Dutch

Seismicity in Flanders

Research output: Book/ReportReport

  • dr Stefan Baisch
  • Christopher Koch
  • dr Elmar Rothert
  • Meike Seidemann
  • dr Robert Vörös
The region of Flanders is characterized by low earthquake activity. Most of the recent earthquakes occur in the Roer Valley Graben, while paleoseismic activity extended into the Campine Basin. However, the stability of tectonic faults in the Campine Basin is not well-understood. Concurrently, anthropogenic activities in the Campine Basin may alter stresses in the subsurface and possibly induce earthquakes.
In this study, we investigate the natural and induced earthquake activity in Flanders to promote a better understanding of seismogenic processes and the role of natural faults in the Campine Basin. Based on our findings, we develop guidelines for managing the risks related to induced seismicity. The study is subdivided into three parts.
In the first part, we build an inventory of the earthquake activity in Flanders based on existing data of the national earthquake services of Belgium (ROB) and neighboring countries. Besides merging different earthquake catalogues, approx. 32 Terabytes of seismogram data were re-processed to detect additional earthquakes of small magnitude. While several hundred additional induced earthquakes were detected, no additional natural earthquakes were found in Flanders. The currently most complete catalogues of earthquakes in Flanders (‘Flanders Catalogue’) and surrounding regions (‘Extended Catalogue’) are accompanying this report.
By comparing the location of earthquakes to the mapped tectonic faults, we find that most natural earthquakes in the Campine Basin can be associated with known faults. Earthquake mechanisms determined in the current study are generally not well-constrained and do not allow to further investigate how individual faults deform. On average, the fault segments on which the earthquakes may have occurred exhibit relatively high levels of tectonic stresses. This implies that the existing model of fault trajectories may help identify regional faults exhibiting little stability. Nevertheless, seismic events induced by activities at two geothermal sites in the Campine Basin do not correlate with any mapped fault. Therefore, even damage relevant seismicity may occur on faults, which are not resolved in the existing fault model.
In the second part of this study, we review the seismic hazard assessment for the geothermal project at Balmatt performed by INERIS. The processes leading to the induced seismicity at Balmatt are not fully understood yet, which is mostly due to insufficient observation data. While the studies by INERIS consider aseismic deformations to play a key role, we favor a more common explanation, where the evolution of seismicity is controlled by hydraulic overpressure in combination with stress changes resulting from previous earthquakes. In our view, predictions of ground vibrations and associated consequences are not sufficiently calibrated in the INERIS study, leading to an underestimation of the associated risks. This is also reflected in the response protocol (‘traffic light system’) that INERIS suggests for future geothermal activities. We feel that the protocol may not be restrictive enough to prevent damage-relevant seismicity at a high confidence level.
In Part III of this study, we provide recommendations for managing induced seismicity risks associated with deep subsurface operations in Flanders. These recommendations are based on global experience, a conceptual geomechanical understanding of the processes causing seismicity and existing practices in neighboring countries. Our recommendations cover a broad range of
subsurface technologies, i.e., geothermal exploitation, gas storage, aquifer-thermal-energy-storage, coal bed methane, mining, carbon capture and storage.
Translated title of the contributionSeismiciteit in Vlaanderen
Original languageEnglish
Number of pages103
Publication statusPublished - 2022

    Research areas

  • P430-mineral-deposits
Log in to Pure