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Abstract:
The source parameter, stress drop, is a key parameter estimating strong ground motion, as it controls the level of peak ground acceleration. Several studies have investigated source parameters for many regions by various methods and assumptions (e.g., Japan, Southern California, and central Italy). In this study, we apply a non-parametric spectral decomposition to isolate the source, site, and path contributions on the Fourier amplitude spectra (FAS) in Europe. We propose the two-domain regionalized attenuation models in the spectral decomposition to take into account the varying attenuation of two spatial domains along the Alps. We download all available data from 1990 to 2020 in Europe through the European Integrated Data Archive (EIDA) within the stream2segment software. The analyzed FAS are selected from 35.6 million recordings which contain 6,135 earthquakes recorded by about 1,600 stations. The final data includes the induced events in Groningen and Poland and some significant events in Italy which provide the opportunity to discuss the variation between induced and natural earthquakes. To derive comparable source parameters in such a large study area, we set one station, LLS (Linth-Limmern), in the Swiss network as a reference site to obtain the corrected source spectra. Finally, we fit the source spectra with a standard ω2-model. The resulting stress drop shows a positive correlation with earthquake magnitude in the magnitude range of 2 to 4.5 and a constant value for larger magnitudes (M>4.5).
