MODELLING OF STRONG GROUND MOTION OF THE JULY 2004, M W 5.2 EARTHQUAKE IN KRN MOUNTAINS (original) (raw)

The effects of the seismic source and of local geology on ground motion are studied in the Upper Soča Valley (western Slovenia), which was struck by two earthquakes, on 12 April 1998 (M W =5.6) and on 12 July 2004 (M W =5.2). The paper focuses on the latter event, while the former was thoroughly investigated in . 2D numerical modelling is applied, together with a recently improved technique of 'sub-structuring' (source and site effect) of the problem at study (DRM approach). Numerical modelling, used for computing site effects, is thereby coupled with an efficient mathematical method used for source modelling. The combined influence of 1D propagation effects on the dominant frequencies of motion, and of 2D effects on the amplification level and significant frequency band, are highlighted. Ground amplification is high in the frequency range of building vulnerability (1-7 Hz), consistent with findings. Comparison with Eurocode 8 spectra shows that the latter may not be conservative for periods up to 0.8 s. The relatively large response at such periods is related to the geological configuration of the valley, which appear to require a reasonably accurate definition of its 2D geometry.

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