Ground motion prediction equations for Vrancea intermediate-depth earthquakes

Vrancea intermediate-depth seismic source dominates the seismic hazard in more than two thirds of the Romanian territory and in Bucharest as well, and it is likely to produce large magnitude earthquakes (M-W > 7.0) several times per century. The paper presents the new ground motion prediction equations (GMPEs) for peak ground acceleration and response spectral accelerations developed for Vrancea intermediate-depth seismic source. The strong ground motion database comprises 465 horizontal components recorded from Vrancea source in earthquakes with moment magnitude in between 5.2 and 7.4 and focal depths ranging from 87 km to 154 km, as well as other 396 horizontal components recorded from subduction intraplate earthquakes worldwide (Chile, India, Japan, Mexico, New Zeeland) with moment magnitude in between 5.6 and 7.8 and focal depths ranging from 69 km to 173 km. The database used in this study is several times larger than the previous ones used in the development of GMPEs for Vrancea intermediate-depth seismic source. The earthquake magnitude, source-to-site-distance and focal depth are considered in the ground motion prediction model. The GMPEs are developed by multiple regression analysis using random mixed effects model. The predicted values are geometric means of ground motion intensity parameters. The total, inter-event and intra-event residuals are analyzed considering several statistical tools and goodness-of-fit parameters. Finally, a comparison is made between the predicted values of ground motion intensity parameters obtained using previous GMPEs developed or recommended for Vrancea subcrustal source and the values obtained using the new attenuation relationship.