Source of the 2008-2010 Walloon Brabant seismic swarm in
the Brabant
Massif revealed !
The small town of Court-Saint-Etienne in Walloon Brabant was struck by a low-magnitude (ML -0.7 to ML 3.2) earthquake sequence from 12 July 2008 until 18 January 2010. 239 events were recorded by the Belgian permanent seismic network that was improved by a local seismic network installed around Court-Saint-Etienne and Ottignies. The seismic sequence was reported regularly in the Belgian media during these 1.5 years as 60 of the 239 events were felt by the local population. In collaboration with Anjana K. Shah (USGS), Dr. Koen Van Noten, Dr. Thomas Lecocq and Dr. Thierry Camelbeeck (ROB) found the causative source of these earthquakes using a multidisciplinary geological, seismological and geophysical approach. By relocating all individual earthquakes, Van Noten and colleagues demonstrated that the seismic activity of these earthquakes occurred along a single, vertical blind fault structure at a depth between 5 km and 7 km below the hamlet of Faux (see Figure). The fault developed in the ~500 million year old, clayey Mousty rock formation of the Brabant Massif. By analysing the variation of magnetic properties of the surrounding rock formations at depth, these authors moreover discovered that this fault is only present at depth and does not continue towards surface to have a surface expression. The results of this BELSPO MO-33-028 project are accepted for publication in Tectonophysics and the authors were congratulated by the journal editor because of the excellence and clear representation of their work.
Van Noten, K., Lecocq, T., Shah, A. & Camelbeeck, T. 2015. Seismotectonic significance of the 2008-2010 Walloon Brabant seismic swarm in the Brabant Massif (Belgium). Tectonophysics doi:10.1016/j.tecto.2015.05.026
