Preliminary Reassessment Results of the Recent Vertical Movements of the Earth's Crust in Bulgaria

Recent vertical crustal movements in Bulgaria have been mapped using adjusted levelling data from three epochs, yet results from different research teams are inconsistent and often contradict known tectonic fault structures. To provide an independent evaluation, we applied a new estimation approach based on data from Bulgaria's Second (1953-1957) and Third (1975-1980) levelling campaigns. Both networks were processed through 3' independent adjustments, selecting line elevations that minimised loop misclosures. In addition, Inverse Distance Weighting (IDW) with a power parameter of 6 was applied. This procedure reduced benchmark height standard errors to below +/- 5.3 mm and vertical velocity errors to +/- 0.30 mm/year. The resulting high-accuracy map reveals a strong correlation between tectonic boundaries and major earthquake epicentres.