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| Titel |
Transfrontier macroseismic data exchange in NW Europe: examples of
non-circular intensity distributions |
| VerfasserIn |
Koen Van Noten, Thomas Lecocq, Klaus-G. Hinzen, Christophe Sira, Thierry Camelbeeck |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250125079
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| Publikation (Nr.) |
 EGU/EGU2016-4609.pdf |
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| Zusammenfassung |
| Macroseismic data acquisition recently received a strong increase in interest due to public
crowdsourcing through internet-based inquiries and real-time smartphone applications.
Macroseismic analysis of felt earthquakes is important as the perception of people can be
used to detect local/regional site effects in areas without instrumentation. We will
demonstrate how post-processing macroseismic data improves the quality of real-time
intensity evaluation of new events. Instead of using the classic DYFI representation in which
internet intensities are averaged per community, we, first, geocoded all individual responses
and structure the model area into 100 km2grid cells. Second, the average intensity of all
answers within a grid cell is calculated. The resulting macroseismic grid cell distribution
shows a less subjective and more homogeneous intensity distribution than the classical
irregular community distribution and helps to improve the calculation of intensity attenuation
functions.
In this presentation, the ‘Did You Feel It’ (DYFI) macroseismic data of several >M4, e.g.
the 2002 ML 4.9 Alsdorf and 2011 ML 4.3 Goch (Germany) and the 2015 ML 4.1 Ramsgate
(UK), earthquakes felt in Belgium, Germany, The Netherlands, France, Luxemburg and UK
are analysed. Integration of transfrontier DYFI data of the ROB-BNS, KNMI, BCSF and
BGS networks results in a particular non-circular, distribution of the macroseismic data
in which the felt area for all these examples extends significantly more in E-W
than N-S direction. This intensity distribution cannot be explained by geometrical
amplitude attenuation alone, but rather illustrates a low-pass filtering effect due to the
south-to-north increasing thickness of cover sediments above the London-Brabant
Massif. For the studied M4 to M5 earthquakes, the thick sediments attenuate seismic
energy at higher frequencies and consequently less people feel the vibrations at the
surface.
This example of successful macroseismic data exchange from multiple seismological
institutions should encourage more seismological institutes to exchange macroseismic data
more often, either in real-time or while post-processing. |
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