Estimation of Macroseismic Intensity–New Attenuation and Intensity VS. Ground Motion Relations for Different Parts of Europe

Abstract eng:
Seismic hazard studies, as well as earthquake early warning systems, are usually focused on estimating the distribution of ground shaking associated with earthquake activity in a given region. Usually, ground shaking levels are presented in terms of peak ground acceleration (PGA), peak ground velocity (PGV) or other recorded parameters. One major drawback of such studies is the very limited strong motion dataset available in many regions even of high seismicity. Furthermore, there is hardly any direct correlation between the distribution of e.g. PGA and damage. To overcome such limitations we study strong ground motion in terms of macroseismic intensity. This makes it possible to include also historical earthquakes in an analysis by using comprehensive intensity point datasets and has the advantage of the results being directly related to the observed earthquake damages. As part of the EC project SAFER (Seismic eArly warning For EuRope), we study the attenuation of macroseismic intensities and derive relations between intensity and recorded ground motion values. Results will be presented for the Marmara Sea area (Turkey), the Naples area (Italy) and the Vrancea area (Romania). We consider a physically constrained attenuation model and account for the finite fault dimensions of large earthquakes in the regressions. Data from several earthquakes are joined, and for the case of Romania, anisotropy in the macroseismic field is accounted for in the derived attenuation model. Relations between intensity and recorded ground motions are based on available strong motion data and the effect of applying different weighting schemes is tested. Results indicate that our regression model provides a reliable estimate of macroseismic intensities for the studied regions, which can be implemented e.g. in seismic hazard analyses or with the USGS ShakeMap software for rapid estimation of the ground motion distribution after a large earthquake.

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