How much was the ground shift by the December 2020 Petrinja (Croatia) earthquake?

2024.06.21.

The December 2020 earthquake near the Croatian town of Petrinja (magnitude 6.4) was felt in all Croatia and in many places in the neighboring countries, and caused serious damage at the site. A recent Croatian-Hungarian collaboration has analyzed the horizontal and vertical displacements caused by the quake and placed them in a regional geodynamic interpretation frame.

Tectonic zones and long-term plate movement speeds around the Petrinja earthquake site (yellow star indicates the epicenter)

The displacements caused by the Petrinja quake have already been estimated in several previous works. The newly published results are methodologically novel in that they use an unprecedented amount of geodetic data to reconstruct three-dimensional motions. In addition to the InSAR data (from Copernicus Sentinel-1 mission), data from three hundred re-occupying GNSS stations of oow-order trigonometric and GNSS networks were processed.

The results showed that the magnitude of horizontal displacements in the epicenter of the earthquake was 40 centimeters in some places, with a maximum of 20 centimeters in the vertical direction.

Horizontal displacements (E-W direction) connected to the Petrinja earthquake, confirmed by radar measurement (surface coloring) and by GPS geodesy (colored point marks) in centimeter units.

The last earthquake of this magnitude in the region was the one in Zagreb in 1880. In the 140 years between the two quakes, the horizontal displacement of the region today, measured by GPS stations, of 2-4 millimeters per year - a local manifestation of plate tectonics - would cause a displacement on the order of the displacement observed in the recent quake. This suggests that displacements due to global tectonics and plate movements in the Petrinja-Zagreb region are realized mostly by individual events, earthquakes, rather than continuous movement. This is important information not only for Croatia when assessing the earthquake safety, but also for the neighboring areas.

Vertical movements of the ground, connected to the 2020 earthquake, in centimeter units.

The article was published in the June 2024 issue of the journal Remote Sensing, first authored by Marko Pavasović, Head of the Chair of State Survey at the University of Zagreb, Faculty of Geodesy, and the corresponding author and author of the geophysics section is Gábor Timár, Head of the Department of Geophysics and Space Science at ELTE.

Link to the paper: https://www.mdpi.com/2072-4292/16/12/2112

(Cover image: Wikipedia)