Datensatz

Zusammenfassung

In areas with medium to moderate seismicity, data on historical earthquakes are crucial in the seismic hazard assessment. Therefore, it is necessary to invest considerable effort in their verification and/or reanalysis. In March 2020, the city of Zagreb (Croatia) was hit by an earthquake of magnitude 5.5 (certainly the strongest one in the last 100 years, and perhaps the strongest after the Great Zagreb 1880 earthquake). Its analysis provided interesting information about the geodynamics of the wider Zagreb area and the Medvednica Mt. Due to these findings, the reanalysis of the Zagreb 1880 event (of magnitude 6.0, and which largely defines the seismic hazard of northwestern Croatia) proved to be a necessity. A detailed macroseismic survey was carried out again, resulting in a new intensity map. Macroseismic field modeling and comparison with empirical intensities were also done, and new geophysical measurements were performed. Based on all the collected information, it can be concluded that the 1880 earthquake was caused by a similar mechanism as in the case of the 2020 earthquake (with hypocenter location in an almost identical place). However, there is a possibility that shortly after the main earthquake there was an aftershock whose location was several kilometers western than the location of the main earthquake. These resulted in the observation of cumulative intensities (cumulative impact of the main earthquake and the strongest aftershock), which has an implication on the epicentral intensity assessment of the main earthquake.