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Ground fissures within the Main Ethiopian Rift: Tectonic, lithological and piping controls
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SYSNO ASEP 0551182 Document Type J - Journal Article R&D Document Type Journal Article Subsidiary J Článek ve WOS Title Ground fissures within the Main Ethiopian Rift: Tectonic, lithological and piping controls Author(s) Valenta, J. (CZ)
Verner, K. (CZ)
Martínek, K. (CZ)
Hroch, T. (CZ)
Buriánek, D. (CZ)
Megerssa, L.A. (CZ)
Boháč, J. (CZ)
Kassa, M. (ET)
Legesse, F. (ET)
Yakob, M. (ET)
Kebede, B. (ET)
Málek, Jiří (USMH-B) RID, ORCID, SAINumber of authors 12 Source Title Earth Surface Processes and Landforms. - : Wiley - ISSN 0197-9337
Roč. 46, č. 15 (2021), s. 3158-3174Number of pages 17 s. Language eng - English Country US - United States Keywords geomechanical properties ; pipe collapses ; pyroclastics ; seismic anisotropy ; soil ; subsurface erosion ; surface waves ; unconsolidated sediments Subject RIV DB - Geology ; Mineralogy OECD category Geology Method of publishing Limited access Institutional support USMH-B - RVO:67985891 UT WOS 000700628100001 EID SCOPUS 85115722867 DOI https://doi.org/10.1002/esp.5227 Annotation Ground fissures, especially if they open due to a sudden collapse of the surface, is a serious risk for populated areas. Their common occurrence in unconsolidated sediments of the Main Ethiopian Rift was found to be mostly a result of piping. The fissures start by piping in linear sub-horizontal underground voids, which often propagate upwards resulting in ceiling collapse and formation of deep and long ground fissures with vertical walls. In the southern and central Main Ethiopian Rift the fissures pose a serious risk to infrastructure and settlements. The ground fissures are often linear (up to several kilometres long and often tens of metres deep) and accompanied by sinkholes (along the length). A detailed field mapping of the geological (rock composition, orientation and character of lithological boundaries, primary fabrics and brittle structures) and geomorphological features (especially a length, width and depth of fissures, sinkholes and gullies) followed by in situ seismic anisotropy measurements and a laboratory determination of the geomechanical properties of volcanoclastic deposits was carried out to investigate the ground fissures' origin. The conditions and factors leading to the formation of the ground fissures have been linked to: (a) the presence of regional normal faults and the associated extensional joints and (b) the alternation of lithological units with contrasting hydraulic permeability. The latter corresponds to a sequence of less permeable hard rocks (e.g., rhyolitic ignimbrites) overlain by heterogeneous, soft and permeable, unconsolidated volcaniclastic deposits with a low amount of clay (less than 10%). The ground fissures' occurrence has shown affiliation to areas which have a significantly high seismic anisotropy (more than 20% at the study sites), which can be used as a proxy to map out high risk areas prone to piping and ground fissure formation. Workplace Institute of Rock Structure and Mechanics Contact Iva Švihálková, svihalkova@irsm.cas.cz, Tel.: 266 009 216 Year of Publishing 2022 Electronic address https://onlinelibrary.wiley.com/doi/10.1002/esp.5227
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