Predictive ground motion scaling in Switzerland: Best estimates and uncertainties |
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| Authors: | Francesca?Bay Email author" target="_blank">Stefan?WiemerEmail author Donat?F?h Domenico?Giardini |
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| Institution: | (1) Swiss Seismological Service, ETH Zurich, Hoenngerberg HPP P5, 8093 Zurich, Switzerland;(2) Interkantonaler Rückversicherungsverband, Bern |
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| Abstract: | Spectral ground motion (1 to 15 Hz) as a function of distance is modeled for events spanning 3.0 <Mw ≤ 7.0 in Switzerland. The parameters required to simulate ground motion with a stochastic approach are inverted from 2958 horizontal and vertical component waveforms of small to moderate size events (2.0 ≤ M{L} ≤ 5.2) in the distance range 10 to 300 km recorded on hard rock sites. Using a Monte Carlo simulation, we establish a significantly different amplification of about a factor of 1.9 between the Alpine Foreland and the Alps. To assess the trade-off between the free parameters of our stochastic model and their influence on the predictive ground motion relationship, we perform a grid search over the five-dimensional solution space. The uncertainties are separated into epistemic and aleatory parts; the main epistemic uncertainty is attributed to the lack of data forM > 5. To constrain the viable models at large magnitudes, results from worldwide scaling studies are evaluated in light of the Swiss data. The model that explains best the low observed stress drops at small magnitudes (Δσ ≅ 3 bar) yet matches observed intensities of historical earthquakes assumes a stress drop increasing with moment asM00.25. For three sites in Switzerland we evaluate the sensitivity of the epistemic uncertainty by computing probabilistic hazard curves. Our model offers the most comprehensive and detailed study of spectral ground motion for Switzerland to date. |
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| Keywords: | attenuation ground motions seismic hazard stress drop Switzerland |
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