Modelling of a Macroseismic Impact Field for Bulgaria

Abstract

Bulgaria, situated in the eastern part of the Balkan Peninsula, is located within the Alpine–Himalayan seismic belt, characterized by high seismic activity. Earthquake activity in Bulgaria and the adjacent region reflects the ongoing geodynamic processes affecting the Balkan Peninsula, where seismicity exhibits significant spatial and temporal variability. In this study, a macroseismic dataset for shallow earthquakes that occurred in and near Bulgaria since the beginning of the 20th century was analyzed. The dataset includes events with moment magnitudes (M_W) ranging from 5.2 to 7.6 and observed intensities from VII to X according to the European Macroseismic Scale (EMS-98). The spatial attenuation of macroseismic intensity was modelled using an elliptical approach, taking into account the regional characteristics of earthquake sources. The results demonstrate a strong correlation between observed and modelled intensities, with correlation coefficients of r > 0.9 and R² > 0.8, confirming the reliability of the proposed attenuation model. The proposed model provides a consistent representation of macroseismic effects and their spatial distribution for strong earthquakes in the region. The proposed approach is applicable to seismic hazard and risk assessment in major urban areas of Bulgaria, particularly Sofia and Plovdiv. The results provide valuable input for seismic risk mitigation, urban planning, infrastructure assessment, and engineering decision-making.