The Zagreb (Croatia) M5.5 Earthquake on 22 March 2020

Abstract

<jats:p>On 22 March 2020, Zagreb was struck by an M5.5 earthquake that had been expected for more than 100 years and revealed all the failures in the construction of residential buildings in the Croatian capital, especially those built in the first half of the 20th century. Because of that, extensive seismological, geological, geodetic and structural engineering surveys were conducted immediately after the main shock. This study provides descriptions of damage, specifying the building performances and their correlation with the local soil characteristics, i.e., seismic motion amplification. Co-seismic vertical ground displacement was estimated, and the most affected area is identified according to Sentinel-1 interferometric wide-swath data. Finally, preliminary 3D structural modeling of the earthquake sequence was performed, and two major faults were modeled using inverse distance weight (IDW) interpolation of the grouped hypocenters. The first-order assessment of seismic amplification (due to site conditions) in the Zagreb area for the M5.5 earthquake shows that ground motions of approximately 0.16–0.19 g were amplified at least twice. The observed co-seismic deformation (based on Sentinel-1A IW SLC images) implies an approximately 3 cm uplift of the epicentral area that covers approximately 20 km2. Based on the preliminary spatial and temporal analyses of the Zagreb 2020 earthquake sequence, the main shock and the first aftershocks evidently occurred in the subsurface of the Medvednica Mountains along a deep-seated southeast-dipping thrust fault, recognized as the primary (master) fault. The co-seismic rupture propagated along the thrust towards northwest during the first half-hour of the earthquake sequence, which can be clearly seen from the time-lapse visualization. The preliminary results strongly support one of the debated models of the active tectonic setting of the Medvednica Mountains and will contribute to a better assessment of the seismic hazard for the wider Zagreb area.</jats:p>

Active Tectonics in the Kvarner Region (External Dinarides, Croatia)—An Alternative Approach Based on Focused Geological Mapping, 3D Seismological, and Shallow Seismic Imaging Data

“…Selected datasets were used as input for the structural modeling of fault planes (Figure 8) performing the inverse distance weight (IDW) point interpolation method, using Move 2019.1 (cf. Markušić et al, 2020).…”

“…This paper presents a multidisciplinary approach to the definition of possible seismogenic faults that include classical geological and structural research on the surface, shallow seismic survey in marine area, and the focused 3D analyses of the selected hypocenters. The 3D modeling of the active faults is here for the first time applied in the area of External Dinarides, following the methodology developed on March 22, 2020, Zagreb earthquake sequence (Markušić et al, 2020). A combination of the results from the various methods allows us to narrow structures that could be active.…”

Back to the future – Andrija Mohorovičić lecture (1909) &amp; Zagreb (2020) M5.5 earthquake

“…The third strong shaking was recorded at 7 hours and 41 minutes, earthquake with magnitude 3.7 according to Richter. In just over 24 hours since the main shock, 57 earthquakes with magnitudes greater than or equal to 2.0 happened in Zagreb (Markušić et al 2020). Zagreb,Croatia.…”

“…Over 1,900 buildings (up to now) are reported to have become uninhabitable by the earthquake damage, particularly buildings built before 1964. In places around the epicenter, the situation was very bad because of the destroyed houses (Figure 8) (Markušić et al 2020).…”

Geological and hydrometeorological hazards and related disasters amid COVID-19 pandemic in Greece: Post-disaster trends and factors affecting the COVID-19 evolution in affected areas

“…Unfortunately, natural hazards and related disasters do not stop for a virus. Only a few months after the initiation of the COVID-19 pandemic, several natural hazards including earthquakes and their primary and secondary effects ( Čivljak et al, 2020 , Markušić et al, 2020 ), hydrometeorological events comprising floods ( Guo et al, 2020 , Frausto-Martínez et al, 2020 ), hurricanes ( Shultz et al, 2020 , Pei et al, 2020 ) and droughts ( Mishra et al, 2021 ) crossed its path. They adversely affected the pandemic evolution in various direct and indirect ways comprising impact on various sectors of the daily life ( Čivljak et al, 2020 , Silva et al, 2020 , Han and He, 2021 , Mishra et al, 2021 , Shen et al, 2021 ).…”