# Destructive M6.2 Petrinja Earthquake (Croatia) in 2020--Preliminary Multidisciplinary Research
###### Abstract
Due to the relatively low level of seismicity of the investigated area in the last 100 years, this has not been observed nor could be investigated. It has strong implications for seismic hazard, and thus for seismic risk, not only in the Pokupsko-Petrinja area, but also (due to its vicinity) in the area of Zagreb, the capital and the cultural, economic and political centre of Croatia and a city in which over 1 million people live. Therefore, immediately after the main earthquake, seismological analyses of the recorded data, along with satellite images and geotechnical data, were initiated. As soon as security conditions were appropriate, field research on geological manifestations and damage that was caused to buildings was conducted. Thus, the first multidisciplinary study of the area was performed (in contrast to the extensive published report [6], which concentrated primarily on the descriptions and distribution of damage to buildings), and significant and hitherto unknown data were obtained, which will contribute to the future assessment of the seismic hazard and risk of this interesting area on the border of the Dinarides and the Pannonian Basin. This paper comprises macrosiessmic, geological, geodetic and civil engineering research. Each discipline is presented in a particular section, summing up the interdisciplinary observations of the analysis at the end of each section as well as in the discussion and the conclusion. The interdisciplinary approach jointly confirmed the assumption of the earthquake origin. It lies in the activation of the complex fault systems on the intersection of two main faults on the strike of the Dinarides (NW-SE). Concerning the methodologies used in the analysis, seismological analysis relied on the Croatian earthquake catalogue, geological study on the orthophoto images and images taken directly on the field after the mainshock, geodetic analysis on the satellite synthetic aperture radar images prior to and after the earthquake, and civil engineered research on seismic intensity maps, earthquake risk assessment, general rules for buildings and their resistance. In the first part of this study, detailed seismological and macroseismic analyses, in combination with geological and geodetic investigations and interpretations, were performed. In the second part, detailed earthquake performances of buildings within Eurocode 8 and macroseismic intensity were analysed and discussed. Finally, peak ground acceleration and response spectra, with consideration of local site effects in the vicinity of the Petrinja M6.2 epicentre, were estimated from the engineering seismology aspect. This is highly important because the results indicate the type of impact the Petrinja M6.2 earthquake will have on future seismic hazard calculations not only in the epicentral area, but also in Zagreb city, as discussed. Since seismic hazard is included in Eurocode 8 provisions, such a multidisciplinary preliminary analysis is highly important for future seismic hazard assessment of earthquake resilience and earthquake resistance design.