The Largest Geodetic Coseismic Assessment of the 2020 Mw=6.4 Petrinja Earthquake

On 28 December 2020, the area of the city of Petrinja was hit by two strong earthquakes of magnitudes 5.0 and 4.7 on the Richter scale, and the following day, 29 December 2020, the same area was hit by an even stronger earthquake of magnitude 6.2. It was one of the two strongest instrumentally recorded earthquakes that hit the territory of the Republic of Croatia in the last hundred years, and the strongest earthquake in the Banovina area after the great earthquake in 1909. Increased seismic activity in this area is caused by two vertical strike-slip faults, Pokupski and Petrinjski. This article aims to determine the displacements of the Earth's crust caused by seismic activity in this area using GNSS measurements and InSAR techniques and comparing their results. Our study showed that horizontal coseismic displacements of 20 cm and more were limited to a radius of 20 km from the epicenter, with a maximum displacement of around half a meter. Considering the original plate tectonic movements of the region and the time elapsed since the previous earthquake of similar magnitude, the geodynamic movements of the Dinarides area are in substantial part sudden displacements associated with earthquakes.