Naslov
Extensive Post-Seismic Cover-Collapse Sinkhole Opening During 2020–2021 Petrinja Earthquake Sequence (Croatia): a Unique Local Geological, Geotechnical and Hydrological Setting

Autori
Tomac, Ingrid ; Vlahović, Igor ; Parlov, Jelena ; Matoš, Bojan ; Matešić, Darko ; Kosović, Ivan ; Pavičić, Ivica ; Frangen, Tihomir ; Terzić, Josip ; Pavelić, Davor ; Kovačević Zelić, Biljana ; Peric, Dunja ; Domitrović, Dubravko ; Vučenović, Helena ; Štambuk Cvitanović, Nataša ; Pham, Nguyen

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
American Geophysical Union Fall Meeting, 13-17 December 2021, New Orleans, LA & Online Everywhere / - , 2021

Skup
American Geophysical Union Fall Meeting

Mjesto i datum
New Orleans (LA), Sjedinjene Američke Države, 13.12.2021. - 17.12.2021

Vrsta sudjelovanja
Poster

Vrsta recenzije
Nije recenziran

Ključne riječi
earthquake ; post-seismic deformation ; cover-collapse sinkholes

Sažetak
After three foreshocks the day before (M5.0, M4.7 and M4.1, respectively), a strong M6.4 Petrinja earthquake occurred on December 29, 2020, followed by thousands of aftershocks (the strongest was a January 6 M5.0 earthquake). This paper presents a unique multihazard sequence of complex events resulting in numerous cover-collapse sinkhole failures. Although the area heavily impacted by the earthquake was larger than 1, 000 km , all 91 sinkholes appeared within a 4 km area surrounding Mečenčani and Borojevići villages located 20–25 km SE of the epicentral area, during the three months following the main earthquake. That area was also previously prone to seldom sinkhole appearances, as evidenced by 45documented fossil sinkholes. All 91 sinkholes opened as post- seismic events ; the first one (the second biggest, 10.8x9.8 m in diameter and 3.6 m deep) started to open six hours after the strongest earthquake. The biggest sinkhole, 25x23 m in diameter and 11.7 m deep, opened seven days after the main earthquake and one day before the strongest aftershock ; its total volume is larger than volume of all other 90 new sinkholes combined. The Mečenčani and Borojevići villages surroundings is the only area where a 4–15 m thick sequence of Holocene soil built of unsaturated low plasticity clays with gravel and sand interlayers and lenses covers the heavily karstified carbonate bedrock composed of alternating highly porous Miocene limestones and calcarenites. The unconfined aquifer within a soil is underlain by a well-permeable confined karst aquifer in which the water pressure during wet periods becomes subartesian to artesian, enabling significant erosion and formation of numerous caverns at the soil–limestone contact. Continuous removal of eroded sediment by groundwater flow through karstified systems in carbonates gradually expands cavernous space until a final cover- collapse. The 2020–2021 Petrinja earthquake sequence significantly accelerated these processes, resulting in 91 cover-collapse sinkholes opened during a three-months period, instead of usually one sinkhole opened every few years as reported by local people. It is interesting to note that during the strongest earthquake the water level in the unconfined aquifer was very close to the surface, and in the underlying karst aquifer artesian conditions prevailed.

Izvorni jezik
Engleski

Znanstvena područja
Geologija, Geofizika, Građevinarstvo

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