A regionally-adaptable ground-motion model for shallow crustal earthquakes in Europe

To complement the new European Strong-Motion dataset and the ongoing efforts to update the seismic hazard and risk assessment of Europe and Mediterranean regions, we propose a new regionally adaptable ground-motion model (GMM). We present here the GMM capable of predicting the 5% damped RotD 50 of PGA , PGV , and SA( T = 0.01 - 8\,s ) SAT=0.01-8s from shallow crustal earthquakes of 3 ≤ MW ≤ 7.4 3≤MW≤7.4 occurring 0 < RJB ≤ 545\,km 0<RJB≤545km away from sites with 90 ≤ Vₛ₃₀ ≤ 3000\,m\,s- 1 90≤Vs30≤3000ms-1 or 0.001 ≤ slope ≤ 1\,m\,m- 1 0.001≤slope≤1mm-1 . The extended applicability derived from thousands of new recordings, however, comes with an apparent increase in the aleatory variability ( σ ). Firstly, anticipating contaminations and peculiarities in the dataset, we employed robust mixed-effect regressions to down weigh only, and not eliminate entirely, the influence of outliers on the GMM median and σ . Secondly, we regionalised the attenuating path and localised the earthquake sources using the most recent models, to quantify region-specific anelastic attenuation and locality-specific earthquake characteristics as random-effects, respectively. Thirdly, using the mixed-effect variance–covariance structure, the GMM can be adapted to new regions, localities, and sites with specific datasets. Consequently, the σ is curtailed to a 7% increase at T < 0.3 s, and a substantial 15% decrease at T ≥ 0.3 s, compared to the RESORCE based partially non-ergodic GMM. We provide the 46 attenuating region-, 56 earthquake localities-, and 1829 site-specific adjustments, demonstrate their usage, and present their robustness through a 10-fold cross-validation exercise.