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| Titel |
Crustal Deformation in Stable Continental Europe: a Comparison of Seismicity, Geodetic and Geologic Information |
| VerfasserIn |
T. Camelbeeck, C. Bruyninx, K. Vanneste, J. Legrand, N. Bergeot, P. Alexandre, S. D. P. Williams, M. Van Camp |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250022454
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| Zusammenfassung |
| Evaluating the maximum magnitude and the recurrence of large earthquakes depend on
where and how the strain is released in the lithosphere. Therefore, to characterize the long
term seismic activity in northwest Europe (NWE), we evaluated and compared the strain
accumulated by the known seismic activity with that observed in the recent geological record
and that deduced from geodetic data.
The consistent re-analysis of GPS data collected by a selection of the EUREF (since 1996),
and WALCORS and FLEPOS permanent networks (since 2003) does not evidence
horizontal crustal movements greater than the uncertainties, and does not allow
identifying regions with strain accumulation. Nevertheless, GPS-based velocities
constrain the maximum value of the present horizontal strain rates to around 5
1010yr-1.
The evaluation of the scalar seismic moment release during historical times suggests that in
western and NW Europe, M ≥ 6.5 - 7.0 earthquakes should be very rare, and that the seismic
strain is relaxed by numerous moderate earthquakes with magnitude between 5.5 and 6.0.
However, the strongest physical constraints on these assumptions will come with the
improved precision of the GPS site velocities as the observation time series become longer.
The earthquake moment release in NWE during the historical period (the last 700 years) is of
the order of 1016 N.m/yr, which corresponds roughly to 40% of the possible maximum
geodetic strain rate for the whole intraplate Europe. An evaluation of the moment release by
the active faults in the Lower Rhine Graben system for the last 10,000 years provides
also a value around 1016 N.m/yr. More specific studies should be undertaken to
confirm these numbers, but they already suggest that, on the long term, the Lower
Rhine Graben system relaxes an important part of the strain in this part of intraplate
Europe.
Repeated absolute gravity measurements across the Belgian Ardenne and the Lower Rhine
Graben system, and in Oostende, on the Belgian coast, suggest that the whole region is
presently subsiding at a rate of 1-2 mm/yr, in agreement with the most recent published
model of the glacial isostatic adjustment (GIA).
The GIA models, validated by geodetic data in the most uplifted area of Fennoscandia GIA,
suggest a NNE-SSW compressive strain in northwest Europe, which is in contradiction with
the strain deduced from earthquake fault-plane solutions and the geological observations in
the Lower Rhine Graben system. This questions the possible relationships between
earthquake activity and GIA. |
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