Empirical relationships between macroseimic intensity and instrumental ground motion parameters for the intermediate-depth earthquakes of Vrancea region, Romania

Empirical relationships between MSK macroseismic intensity and several engineering ground motion parameters are developed using the macroseismic and instrumental data available for five significant earthquakes (Mw magnitude 6 and above), which occurred during the past half-century in Vrancea region, Romania. The relations are suitable for the Carpathian bend zone and surroundings, and they are valid for intensity values between 5 and 8; in this range, the MSK intensity is basically defined by the level of structural damage. The capability of the selected ground motion parameters to predict the macroseismic intensity is evaluated by observing the standard deviations associated with the proposed regression models. Generally, the parameters which take into account the ground motion duration appear to be more stable predictors than the parameters based on the peak ground motion. The most reliable damage indicator appears to be the Arias intensity. The proposed regression relationships provide intensity predictions with uncertainty close to one-half unit; therefore, they are reliable tools for rapid loss estimation and emergency response coordination following a strong earthquake of Vrancea region. The derived equations represent also useful instruments for seismic risk assessment by methodologies based on macroseismic intensity, since in current practice the earthquake hazard and seismic impact are mainly given in terms of engineering ground motion parameters.