Preliminary engineering geological and geotechnical investigation of geological hazards induced by Petrinja Earthquake Series 2020-2021

Following the earthquake with an epicentre in Petrinja (magnitude ML = 6.2 and maximum horizontal accelerations of 0.4 < PGAsite < 0.6 g), several types of geohazards were triggered. This paper describes preliminary engineering-geological and geotechnical investigations conducted immediately after the main earthquake, over an approximate period of six months, in order to enable an assessment of the impact of the catastrophic earthquake in the form of risk evaluation for the entire affected area. The main results of these preliminary investigations are geohazard maps showing an inventory of geohazard occurrences and zoning based on the spatial probability of geohazard occurrence, produced for an area of approximately 3,600 km². Their long-term application for seismic-geotechnical microzonation of the area affected by the catastrophic earthquake is also highlighted. It is concluded that the preliminary engineering-geological and geotechnical investigations of earthquake-induced geohazards were essential both for post-disaster crisis management and for managing the risk of future catastrophic earthquakes, as they represent a mitigation and prevention tool that can be continuously applied in spatial planning at all levels.