Consentino, Bruno Cirilo

Bachelor thesis supervised by Van Noten, Koen; Sintubin, Manuel (KULeuven)

Abstract: Macroseismic intensity assessment is important because positioning of sufficient seismometers and accelerometers in a vast territory to detect earth’s movement in local scale is expensive and difficult. In this work “Did You Feel It?” (DYFI) data collected by online questionnaires by the Royal Observatory of Belgium (ROB) are used to map the intensity of earthquakes in the 2008-2010 Walloon Brabant seismic swarm to investigate relationship between magnitude and depth with impact and perception of tremors by people in the region for this seismic swarm. Instead of producing classical Community Internet Intensity Maps (CIIM), in which earthquake intensity is shown for each community, we apply a Grid Cell procedure of the DYFI data in a GIS environment (QGIS) to ensure a better and more homogeneous spread of the intensity values. Sound perception of earthquakes is also assessed in grid cells but remains enigmatic, no distribution pattern could be clearly defined. This can be due to the fact that the scale of sound perception is too subjective. Plots of intensity against distance from epicenter are analysed and compared to Central and Eastern United States (CEUS) Attenuation models (Atkinson and Wald 2007). Intensity grids and attenuation graphs show decreases of intensity with distance in all directions. They also show that depth of earthquake influence perception of intensity. Deeper, higher-intensity tremors can be widely felt but can have lower intensity around epicenter than shallower, lower-magnitude earthquakes. CEUS Attenuation models proved inadequate in modeling impact of earthquakes from the seismic swarm, thus development of a specific attenuation model for central Belgium is advisable to improve the assessment of the seismic risk.

Keyword(s): Did You Feel It? ; mapping ; earthquake ; macroseismology