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| Titel |
The seismotectonic significance of the 2008-2010 seismic swarm in the Brabant Massif (Belgium) |
| VerfasserIn |
Koen Van Noten, Thomas Lecocq, Anjana K. Shah, Thierry Camelbeeck |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250104793
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| Publikation (Nr.) |
 EGU/EGU2015-4229.pdf |
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| Zusammenfassung |
| Structural interpretations of the tectonic grain of orogenic mountain belts have often been
based on the study of potential field data. The steep architecture of mountain belts can be
highlighted by the inclination of the magnetic field and by the persistence of aeromagnetic
lineaments with depth. With respect to seismology, matched filtering has proven to be very
useful for linking seismicity with deep-seated tectonic structures by separating
short-wavelength anomalies, that originate from shallow depths, from long-wavelength
anomalies that generally originate at greater depths.
Between 2008 and 2010 more than 300 low-magnitude earthquakes occurred 20 km SE of
Brussels (Belgium). Thanks to a locally deployed temporary seismic network covering the
epicentral area, very small events could be detected (magnitude variation between ML -0.7
and ML 3.2). The spatial distribution of the hypocenter locations show a dense spatial cluster
displaying a narrow, 1.5-km long, NW-SE oriented fault zone at a depth range between 5 and
7 km, located in the Cambrian basement rocks of the Lower Palaeozoic Anglo-Brabant
Massif. Its NW-SE orientation is in agreement with the structural grain in this part of the
Brabant Massif.
In order to find a relevant tectonic structure that could correspond to the 2008-2010 seismic
swarm, we present a full seismotectonic analysis linking local geology to the seismic swarm.
A systematic filtering approach was applied in which the magnetic field was carefully
bandpass filtered to generate different aeromagnetic maps that highlight sources near the
hypocenter depths. Filtering demonstrates that the structure responsible for the seismic
swarm is limited in length as it is bordered at both ends by magnetic lineaments
with different orientations than the seismic swarm. These observations explain the
rather limited spatial distribution of the swarm, both in a vertical and horizontal
direction.
Although few of the largest historical seismic events in Belgium occurred within the borders
of the Brabant Massif, the limited fault length thus suggests that, given its favourable
orientation to reactivation in the current stress configuration, it potentially could result in a
reduced seismic hazard for this region. |
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