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2020 earthquakes in Croatia: initiatives, activities and strategies of reconstruction process

Although Croatia is located in a seismically active region, seismic risk awareness was very low before the unfortunate events of 2020. First, amidst the COVID-19 lockdown, a ML5.5 earthquake struck Zagreb. Then, at the end of the year on December 29, a ML6.2 (Mw6.4) earthquake struck Petrinja, preceded by a ML5.0 event. In these events, city cores with invaluable cultural heritage buildings were significantly affected, as well as many family houses, mostly built of unreinforced masonry. The system for assessments of damage and usability of buildings was improvised and despite the shortcomings of official disaster response system in the preparation phase, it worked relatively well, mainly thanks to the sacrifice of many individual volunteers who eventually carried out more than 26.000 inspections after the Zagreb and almost 50.000 after the Petrinja earthquakes. After the initial shock, the relevant institutions prepared the Law on reconstruction which was primarily intended to enable the affected communities to recover more quickly. In parallel, the expert guidelines for reconstruction were published at the end of June 2020 as amendments to the Technical Regulation for Structures. The reconstruction methods and guidelines are specified depending on the building use and the degree of damage. Interventions are proposed to improve the seismic behaviour of buildings without high economic costs and relocation of occupants. Residents are made aware that the capacity of the damaged buildings was already low before the earthquake and that it is practically impossible to attain the capacity required by current standards. Each reconstructed building will eventually receive a seismic certificate. In parallel with the legal framework, the researchers and professionals have jointly carried out many activities to raise knowledge among civil engineering community (e.g. free webinars were organized, a book on the urgent retrofit measures and a comprehensive reconstruction manual were published, etc.). Moreover, Croatian centre for earthquake engineering was (finally) officially established to build capacity for all currently required activities, but especially for strategic seismic risk mitigation that should be done in cooperation with relevant institutions. At the end of 2021, systematic reconstruction has not yet accelerated. There are many reasons for this, but the most important is the very complex relationship between the multi-apartment buildings owners, the historic value of the affected urban cores, which needs to be tackled very carefully from many aspects, and the complex documentation required to apply for reconstruction funds. In summary, these earthquakes were a great warning to everyone in the region, to take the necessary strategic steps aimed at seismic risk reduction.

earthquake ; usability inspections ; damage ; retrofit

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