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Intensity‐attenuation and magnitude‐intensity relationships for northwest european earthquakes
Author(s) -
Ambraseys N.
Publication year - 1985
Publication title -
earthquake engineering and structural dynamics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.218
H-Index - 127
eISSN - 1096-9845
pISSN - 0098-8847
DOI - 10.1002/eqe.4290130604
Subject(s) - attenuation , intensity (physics) , magnitude (astronomy) , epicenter , seismology , geology , intraplate earthquake , attenuation coefficient , induced seismicity , radius , absorption (acoustics) , geodesy , physics , tectonics , optics , computer security , astronomy , computer science
Abstract This study shows that, for Northwest Europe, an intraplate region of subdued seismicity, a comparatively simple attenuation model is adequate to predict quite accurately the fall‐off of intensity with distance. The analysis shows that focal depths determined from macroseismic data are confined in the upper 25 km, and that shallow shocks attenuate far more rapidly than deeper events. There is no evidence for a regional variation of the absorption coefficient, which, together with the coefficient of geometric spreading, is a function of depth. Also, the intensity factor b, which is usually taken to be equal to 3, is a variable and a function of the energy absorption at the epicentre. It is shown that magnitudes can be predicted accurately by use of one or preferably by more isoseismal radii calibrated against re‐assessed instrumental magnitudes.