000005440 001__ 5440
000005440 005__ 20211001130709.0
000005440 037__ $$aCTALK-2021-0073
000005440 100__ $$aNeefs, Ben
000005440 245__ $$aThe Effects of Belgian Crustal Geology and its Sedimentary Cover on Macroseismic Intensity Attenuation
000005440 260__ $$c2021
000005440 269__ $$c2021-09-17
000005440 520__ $$aTo quickly assess the impact of earthquakes, many countries make use of earthquake intensity prediction equations (IPEs). These empirical equations describe the decay of ground motion in terms of macroseismic intensity and consequently can simulate the damage distribution and damage degree in near real-time. Intensity attenuation is region-specific and is dependent on seismic wave propagation in the crust and its sedimentary cover. To develop IPEs suitable for modelling the impact of Belgian earthquakes, local macroseismic data is thus required. The Royal Observatory of Belgium (ROB) has a rich heritage in collecting felt earthquake and damage reports. This database was extended by intensity data from neighboring countries and is used to develop Belgian IPEs. However, the traditional methodology, i.e. constructing a single intensity attenuation law for large areas, is not fit for the complex geological situation in Belgium. Macroseismic intensity distribution patterns of past Belgian earthquakes do not cohere to the common assumption of an isotropic intensity decrease with increasing epicentral distance. Intensity attenuation is strongly influenced by crustal and cover geological features that heavily control and limit seismic wave propagation and cause an anisotropic display of intensity decay. Geological features that have influenced past intensity distribution patterns and attenuation in Belgium are: - The strongly compacted and deformed Lower Palaeozoic Anglo-Brabant Massif, which easily transfers ground motion along its core axis in a WNW-ESE direction. - The increasing thickness of soft sedimentary Cenozoic strata covering the Anglo-Brabant massif towards the Belgium-Dutch border, effectively filtering high-frequency ground motions. - The Lower Rhine Embayment boundary faults, impeding effective ground motion transfer and serving as seismic mirrors. - The Midi-Eifel Fault which separates the Ardenne allochthon from its foreland and acts as a seismic barrier. - The shallow Walloon Carboniferous coal basins along a thin band across the country with a fast intensity attenuation. The quantitative effect of these geological regions on macroseismic intensity are best to be modelled separately, with different IPEs for each characteristic region in Belgium. But given the small size of both Belgium and these regions, local earthquakes are prone to hit multiple areas with different attenuation properties at once. This urges the necessity to subselect macroseismic data out of different earthquakes to be able to model IPEs independently. Furthermore, modelling anisotropic intensity decay requires an additional dimension, e.g. such as bedrock depth, to be added to the prediction equation, which is uncommon in literature and further complicates this goal. The complex Belgian geology thus requires an entire new methodology to be developed to be able to construct Belgian IPEs, which will be elaborated in detail in this presentation.
000005440 536__ $$aPhD ROB funding/$$cPhD ROB funding/$$fPhD ROB funding
000005440 594__ $$aNO
000005440 6531_ $$aMacroseismology
000005440 6531_ $$aRegional Attenuation 
000005440 6531_ $$aIntensity Prediction Equation
000005440 700__ $$aVan Noten, Koen
000005440 700__ $$aCamelbeeck, Thierry
000005440 773__ $$t7th INTERNATIONAL GOGICA BELGICA  MEETING 2021
000005440 8560_ $$fben.neefs@observatory.be
000005440 8564_ $$s3449856$$uhttp://publi2-as.oma.be/record/5440/files/Geologica_Belgica_2021-Neefs_Ben.pdf
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000005440 906__ $$aContributed
000005440 980__ $$aCTALKCONT