October the 19th, 2026 – A new interactive earthquake map reveals here the danger in Croatia is the greatest, with southern Croatia in particular in quite the precarious spot.
Croatian scientists have produced a new seismic hazard assessment for Croatia that incorporates the experiences of the Petrinja earthquake and data on the soil beneath our cities. Index/Nenad Jaric Dauenhauer reports that the danger is greatest along the Adriatic coast, especially down south in the wider Dubrovnik area. The results also reveal something a little less obvious: for low and rigid buildings, including family houses, the new assessment along the coast and far inland in the area of Petrinja gives higher seismic loads than those prescribed, while for high buildings, it mostly gives lower ones.
This new map could serve as a scientific basis for a new Croatian national annex to Eurocode 8, the European standard for earthquake-resistant construction. It describes how strongly the ground could shake, with a certain probability, but it does not announce the date of the next earthquake nor does it itself reveal which building will survive.
why does croatia need a new earthquake map?
The Zagreb earthquake of magnitude 5.5 that struck back in March 2020 and the Petrinja earthquake of magnitude 6.2 later that same year in December showed just how devastating the combination of strong shaking and vulnerable buildings can be. Dubrovnik was almost destroyed in 1667 by an earthquake of estimated magnitude around 7, and Zagreb was struck in 1880 by an earthquake of magnitude around 5.9.
“Destructive earthquakes here are not a footnote in history. That is precisely why probabilistic seismic hazard assessment is the right framework for design and spatial planning across Croatia,” explained Professor Snježana Markušić from the Geophysical Department of the Faculty of Science (PMF) in Zagreb, the first author of the paper. The current Croatian seismic hazard map, an integral part of the national annex to Eurocode 8 from back in 2011, is based on earlier research. In the meantime, scientists have collected new earthquake records and data on local soil conditions, and in 2024 the second generation of Eurocode 8 was also published.
The new assessment was prepared by Snježana Markušić, Iva Žilić, Tomislav Fiket and Anja Majurec from the Geophysical Department of PMF in Zagreb, Davor Stanko from the Faculty of Geotechnical Engineering in Varaždin, and Tvrtko Korbar from the Croatian Geological Survey. The paper was published on the 17th of September 2026 in the journal Bulletin of Earthquake Engineering (BEE).
earthquakes don’t care about borders
Seismic hazards in Croatian cities are also influenced by earthquakes outside of Croatia. For Dubrovnik, for example, the seismic areas located on the territories of both Montenegro and Albania are very important. That is why the processed area is considerably wider than Croatia. Foreshocks and aftershocks were removed from the earthquake catalogue, because the model describes the long-term frequency of mainshocks. “90,003 mainshocks remained, only 14.9 percent of all recorded events. Almost three quarters were aftershocks,” says Tomislav Fiket from PMF.
The authors divided the wider area of Croatia and neighbouring countries into 32 zones according to geological structure, seismic activity and faults, and performed the calculations in the open-source program OpenQuake. “Three large tectonic units – the Adriatic Foreland, the Dinarides and the Pannonian Basin – create very different conditions in the Earth’s crust, so faults across the country move in different ways. We incorporated that diversity into the model, for each zone separately,” explains Tvrtko Korbar from the Croatian Geological Survey.
Two similar houses, one on solid rock and the other on thick deposits of softer soil, will not shake equally during the same earthquake, because softer deposits can amplify the shaking. An important novelty of the paper is therefore the inclusion of soil data, instead of calculating only for solid rock. “A model that includes the actual surface of the terrain directly encompasses the amplification of shaking due to local soil, instead of it being subsequently estimated with a simplified factor,” says Davor Stanko from the Faculty of Geotechnical Engineering. How important local differences are is also shown by a study of Zagreb published in 2025, in which Markušić and Stanko participated. It turned out that in the central and south-eastern parts of the city thick, unconsolidated deposits can amplify seismic waves.
dubrovnik and central dalmatia are areas of concern
The overall seismic hazard is by far the greatest along the coastline, especially down in the Dubrovnik-Neretva area and a little further north in central Dalmatia. Scientists express this danger by the maximum ground acceleration during shaking, in units of g. One g is equal to the acceleration of gravity (9.81 m/s²), so a value of 0.40 g means that the maximum horizontal ground acceleration during shaking reaches 40 percent of that amount. The greater the acceleration, the greater the loads buildings are generally exposed to, but their response also depends on the properties of the structure.
With actual soil conditions taken into consideration, the new assessment gives around 0.40 g across Dubrovnik, 0.32 g in Split, 0.27 g in Rijeka, 0.24 g in Zagreb, 0.22 g in Petrinja and 0.08 g in Osijek. This means that in each of those cities there is about a 10 percent probability that the peak ground acceleration in the next 50 years will exceed the stated value. This is not the strongest possible shaking, nor is it the magnitude of the earthquake: magnitude describes the energy released at the earthquake focus, while ground acceleration describes how strongly the ground shakes at a particular place. “The areas of Sisak, Moslavina and Petrinja, despite the strong earthquake sequence of 2020, according to our results belongs to the group of moderate hazard,” says Markušić. Nevertheless, even weaker shaking can cause great damage if buildings are poorly constructed.
earthquakes have no schedule
The information that a certain level of shaking has a return period of 475 years is easily misleading. It does not mean that such shaking comes once every 475 years and that after it follows centuries of calm. It’s a statistical description: the annual probability of exceedance is about 0.2 percent, which over 50 years, the usual lifespan of a building, accumulates to about 10 percent. The model assumes that earthquakes have no “memory”, as with rolling a die: the previous result does not determine the next one. For critical infrastructure a rarer, stronger shaking is also important, with a return period of 2,475 years and about a 2 percent probability of exceedance in 50 years.
what a single house does and what a building does during an earthquake are very different…
Every building has a natural period of oscillation, the time of one full swing, and it amounts to about a tenth of a second per storey: a family house oscillates with a period of about 0.1 to 0.2 seconds, and a building of about ten storeys with a period of about one second. A building sways most strongly when oscillations of a period similar to its own predominate in the ground motion, similar to a swing that we push at the right moment. According to the new assessment, that shaking is strongest in all the observed cities for a period of 0.2 seconds, i.e. precisely for low buildings.
That’s why low and rigid buildings on the coast and in Petrinja could be exposed to higher seismic loads than those provided for by the current design spectrum. For high and flexible buildings, which sway more slowly, the new assessment almost everywhere gives lower loads than those prescribed. The comparison is nevertheless not entirely equal because the current spectrum refers to solid rock, while the new assessment also includes local soil.
“The results indicate that a map prepared for a uniform reference rock, when local soil is taken into account, can in some places underestimate and in others overestimate the hazard. There is no single correction factor applicable throughout the country,” Markušić explains.
“For the faults responsible for the strongest earthquakes in Croatia, such as the Petrinja and Pokupsko faults, there are still not enough complete data for them to be reliably modelled separately. Their inclusion is a priority for the next generation of models,” explained Korbar. “Croatia’s database of strong earthquake records is still relatively small. Its expansion, together with the preparation of a more detailed national soil database, is one of the key next steps,” adds Žilić.
will the new map force construction rule changes?
The new research represents a scientific study of probabilistic seismic hazard assessment, not a national annex to the standard, and does not prescribe legally binding design values. “We offer a scientific basis on which the competent authorities can rely when they start preparing the new annex that Croatia must adopt for the second generation of Eurocode 8,” Markušić emphasises. The new Croatian earthquake danger map will therefore not change the regulations overnight. It gives the competent authorities a new basis for decisions, and citizens a clearer picture of the hazard. The safety of an individual building still needs to be assessed according to its structure, condition and the soil on which it stands. The greatest value of the new map will be that better knowledge about earthquakes is turned into safer construction.
