Department of Seismotectonics
Institute of Rock Structure and Mechanics of the CAS

Services & Expertise International Cooperation Software
Basic Information Research Activities Most important results Projects

Ground Fissures within the Ethiopian Main Rift: Tectonic, Lithological and Piping Controls

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.

Publication: Valenta, J., K. Verner, K. Martínek, T. Hroch, D. Buriánek, L. A. Megerssa, J. Boháč, M. Kassa, F. Legesse, M. Yakob, B. Kebede and J. Málek (2021). Ground fissures within the Main Ethiopian Rift: Tectonic, lithological and piping controls, Earth Surface Processes and Landforms. 1-17, DOI:10.1002/esp.5227

Fig.: Ground fissures in the MER, and especially their sudden opening, is one of the most significant geoohazard in the area. The fissures open in unconsolidated sediments and are long (even several kilometres), narrow (0.5 to several metres), deep (usually several meters but maximum depth measured was 60 m) and fast opening (even several hundred meters in half a year). The fissures are oriented perpendicular to the main direction of extension (parallel to the Rift).

Fig.: WEBNET seismic stations (triangles) with available data (31 May 2014).
WEBNET location of strongest event (star) is also depicted.

Focal Mechanisms of West Bohemia, Central Europe, Earthquakes - End of May 2014: Evidence of Volume Changes

West Bohemia is a region with a lot of mineral springs and gas outflows. We focused on the strongest earthquake over the past thirty years (May 31, 2014; Mw~3.8) and on two smaller ones (Mw~2.9; 2.5) from the same day. The main goal of this study is to contribute to clarification of the nature of earthquake swarms in the western edge of the Bohemian Massif. Negative value of the isotropic part of full moment tensor could be related to the closing of cracks and fissures during a rupture process.

Publication: Křížová, D. and J. Málek (2021): Focal Mechanisms of West Bohemia, Central Europe, Earthquakes-End of May 2014: Evidence of Volume Changes, Seismological Research Letters 92(6), 3398-3415, DOI: 10.1785/0220200389

Fig.: Focal mechanism plot for the strongest earthquake (31 May 2014, 10:37:21.11) with signs of first motion for available WEBNET data. Black squares mean "up" and white "down"; T and P axes are depicted by circles.

Further important publications and outputs

Lenhardt, W. A., D. Paseresi, M. Živčić, G. Costa, T. Fiket, I. Bondár, L. Duni, P. Špaček, L. Dimitrova, C. Neagoe, D. Malytskyy, K. Csicsay, L. Tóth and L. Fojtíková (2021). Improving Cross-Border Seismic Research: The Central and Eastern Europe Earthquake Research Network (CE3RN), Seismol. Res. Lett. 92(3), 1522-1530, DOI:10.1785/0220200374

Rahnema, H., S. Mirassi and G. Dal Moro (2021). Cavity effect on Rayleigh dispersion and P-wave refraction, Earthq. Eng. & Eng. Vib. 20, 79-88, DOI: 10.1007/s11803-021-2006-y

Dal Moro, G. (2020). Efficient joint analysis of surface waves and introduction to vibration analysis: Beyond the clichés, Springer, pp. 1-266. DOI: 10.1007%2F978-3-030-46303-8

Křížová, D. and J. Málek (2021). Focal Mechanisms of West Bohemia, Central Europe, Earthquakes-End of May 2014: Evidence of Volume Changes, Seismol. Res. Lett. 92(6), 3398-3415, DOI: 10.1785/0220200389

Brokešová, J., J. Málek, J. Vackář, F. Bernauer, J. Wassermann and H. Igel (2021). Rotaphone-CY: The Newest Rotaphone Model Design and Preliminary Results from Performance Tests with Active Seismic Sources, Sensors, 21, 562, DOI: 10.3390/s21020562

Ademović, N., V. Demir, S. Cvijić-Amulić, J. Málek, I. Prachař and J. Vackář (2021). Compilation of the seismic hazard maps in Bosna and Herzegovina, Soil Dyn. Earthq. Eng., 141, 106500, DOI: 10.1016/j.soildyn.2020.106500

Bernauer, F., K. Behnen, J. Wassermann, S. Egdorf, H. Igel, S. Donner, K. Stammler, M. Hoffmann, P. Edme, D. Sollberger, C. schmelzbach, J. Robertsson, P. Paitz, J. Igel, K. Smolinski, A. Fichtner, Y. Rossi, G. Izgy, D. Vollmer, E. P. S. Eibl, S. Buske, C. Veress, F. Guattari, T. Laudat, L. Mattio, O. Sèbe, S. Olivier, C. Lallemand, B. Brunner, A. T. Kurzych, M. Dudek, L. R. Jaroszewicz, J. K. Kowalski, P. A. Bońkowski, P. Bobra, Z. Zembaty, J. Vackář, J. Málek and J. Brokešová (2021). Rotation, Strain, and Taranslation Sensors Performance Tests with Active Seismic Sources, Sensors, 21, 264, DOI: 10.3390/s21010264

Sana, H., P. Tábořík, J. Valenta, F. A. Bhat, J. Flašar, P. Štěpančíková and N. A. Khwaja (2021). Detecting active faults in intramountain basins using electrical resistivity tomography: A focus on Kashmir Basin, NW Himalaya, J. Appl. Geophys, 192, 104395, DOI: 10.1016/j.jappgeo.2021.104395

Stabile, T. A., J. Vlček, M. Wcisło and V. Serlenga (2021). Analysis of the 2016-2018 fluid-injection induces seismicity in the High Agri Valley (Southern Italy) from improved detections using template matching, Sci. Rep., 11, 20630, DOI: 10.1038/s41598-021-00047-6

Pšenčík I., M. Wcisło and P. F. Daley (2021). SH plane-wave reflection/transmission coefficients in isotropic, attenuating media, Journal of Seismology, DOI: 10.1007/s10950-021-10052-x

List of publication 2021
List of publication 2015-2020

Further publications in ASEP database