Measurements of tectonic micro-displacements within the Idrija fault zone in the Učja valley (W Slovenia)

  • Andrej Gosar Slovenian Environment Agency, Seismology and Geology Office, Ljubljana
Keywords: tectonics, geodynamics, fault, extensometer, Idrija fault, Učja, Slovenia


A recent slip-rate of an active fault is a very important seismotectonic parameter, but not easy to determine. Idrija fault, 120 km long, is a prominent geomorphologic feature with large seismogenic potential, still needed to be researched. Measurements of tectonic micro-displacements can provide insight into its recent activity. The Učja valley extends transversally to the Idrija fault and was therefore selected for the installation of TM 71 extensometer. Measurements on the crack within its inner fault zone are conducted from the year 2004. In 14 years of observations a systematic horizontal displacements with average rate of 0.21 mm/year and subordinate vertical displacements of 0.06 mm/year were established, proving the activity of this fault. An overview of methods of displacement measurements related to active faults and of newer interdisciplinary investigations of the Idrija fault is given. Displacement rates are beside for geodynamic interpretations important for improvement of seismotectonic models and thus for better seismic hazard assessment.


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ARSO 2015: Digital elevation model of Slovenia – 1 m resolution. Slovenian Environment Agency. Ljubljana.

Atanackov, J., Bavec, M., Celarc, B., Jamšek Rupnik, P., Jež, J., Novak, M., Milanič, B. 2014: Seizmotektonska parametrizacija aktivnih prelomov Slovenije. 1. del. Geološki zavod Slovenije, Ljubljana.

Atanackov, J., Jamšek Rupnik, P., Jež, J., Milanič, B., Novak, M., Celarc, B., Bavec, M. 2016: Database of active faults in Slovenia. Procedings of the 7th International INQUA Meeting on Paleoseismology, Active Tectonics and Arheoseismology. Crestone.

Bajc, J., Aoudia, A., Saraò, A., Suhadolc, P. 2001: The 1998 Bovec-Krn mountain (Slovenia) earthquake sequence. Geophysical Research Letters 28-9. DOI:

Baroň, I., Plan, L., Sokol, L., Grasemann, B., Melichar, R., Mitrovic, I., Stemberk, J. 2019: Present-day kinematic behaviour of active faults in the Eastern Alps. Tectonophysics 752. DOI:

Bavec, M., Atanackov, J., Celarc, B., Hajdas, I., Jamšek Rupnik, P., Jež, J., Kastelic, V., Milanič, B., Novak, M., Skaberne, D., Žibret, G. 2013: Evidence of Idrija fault seismogenic activity during the Late Holocene including the 1511 Mm 6.8 earthquake. Seismic hazard, critical facilities and slow active faults: proceedings of the 4th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology. Aachen.

Briestenský, M., Košťák, B., Stemberk, J., Petro L., Vozár, J., Fojtíková, L. 2010: Active tectonic fault microdisplacement analyses: a comparison of results from surface and underground monitoring in western Slovakia. Acta Geodynamica et Geomaterialia 7-4.

Buser, S. 1986: Osnovna geološka karta SFRJ 1 : 100.000, lista Tolmin in Videm. Zvezni geološki zavod, Beograd.

Cunningham, D., Grebby, S., Tansey, K., Gosar, A., Kastelic, V. 2006: Application of airborne LiDAR to mapping seismogenic faults in forested mountainous terrain, SE Alps, Slovenia. Geophysical Research Letters 33. DOI:

Čar, J. 2010: Geološka zgradba idrijsko-cerkljanskega hribovja. Tolmač h Geološki karti idrijsko-cerkljanskega hribovja med Stopnikom in Rovtami v merilu 1 : 25 000. Geološki zavod Slovenije, Ljubljana.

Čar, J., Gosar, A. 2011: Idrijski prelom in premiki ob njem. Idrijski razgledi 56-1.

Čar, J., Pišljar, M. 1993: Presek Idrijskega preloma in potek doline Učje glede na prelomne strukture. Rudarsko-metalurški zbornik 40, 1-2.

Fitzko, F., Suhadolc, P., Aoudia, A., Panza, G. F. 2005: Constraints on the location and mechanism of the 1511 Western-Slovenia earthquake from active tectonics and modeling of macroseismic data. Tectonophysics 404, 1-2. DOI:

Ganas, A., Gosar, A., Drakatos, G. 2008: Static stress changes due to the 1998 and 2004 Krn Mountain (Slovenia) earthquakes and implications for future seismicity. Natural Hazards and Earth System Science 8-1. DOI:

GeoZS, 2016: Seizmotektonska parametrizacija aktivnih prelomov Slovenije. Geološki zavod Slovenije, Ljubljana.

Gosar, A. 2007: Monitoring of micro-deformations along Idrija and Raša faults in W Slovenia. Geologija 50-1. DOI:

Gosar, A. 2012: Application of Environmental Seismic Intensity scale (ESI 2007) to Krn Mountains 1998 Mw=5.6 earthquake (NW Slovenia) with emphasis on rockfalls. Natural Hazards and Earth System Science 12-5. DOI:

Gosar, A. 2019a: Review of geological and seismotectonic investigations related to 1998 Mw5.6 and 2004 Mw5.2 earthquakes in Krn Mountains. Geologija 62-1. DOI:

Gosar, A. 2019b: Review of seismological investigations related to 1998 Mw5.6 and 2004 Mw5.2 earthquakes in Krn Mountains. Geologija 62-1. DOI:

Gosar, A. 2019c: The size of the area affected by earthquake induced rockfalls: Comparison of the 1998 Krn Mountains (NW Slovenia) earthquake (Mw 5.6) with worldwide data. Acta geographica Slovenica, 59-1. DOI:

Gosar, A., Šebela, S., Košťák, B., Stemberk, J. 2007: Micro-deformation monitoring of active tectonic structures in W Slovenia. Acta Geodynamica et Geomaterialia 4-1.

Gosar, A., Šebela, S., Koštak, B., Stemberk, J. 2009: Surface versus underground measurements of active tectonic displacements detected with TM 71 extensometers in western Slovenia. Acta Carsologica 38, 2-3. DOI:

Gosar, A., Šebela, S., Košťák, B., Stemberk, J. 2011: On the state of the TM71 extensometer monitoring in Slovenia: Seven years of micro-tectonic displacement measurements. Acta Geodynamica et Geomaterialia 8-4.

Kogoj, D. 2000: Geodetske meritve stabilnosti tal ob tektonskih prelomih na območju Slovenije. Geodetski vestnik 44, 1-2.

Košťák, B. 1977: Terčové mĕřidlo TM-71 a jeho užití pro mĕření velmi pomalých pohybů na poruchách a trhlinách. Inž. Stavby 25-5.

Košťák, B. 1991: Combined indicator using Moire technique. Proceedings of the 3rd international symposium on field measurements in geomechanics. Oslo.

Moulin, A., Benedetti, L., Gosar, A., Jamšek Rupnik, P., Rizza, M., Bourles, D., Ritz, J.-F. 2014: Determining the present-day kinematics of the Idrija fault (Slovenia) from airborne LiDAR topography. Tectonophysics 628. DOI:

Moulin, A., Benedetti, L., Rizza, M., Jamšek Rupnik, P., Gosar, A., Bourles, D., Keddadouche, K., Aumaitre, G., Arnold, M., Guillou, V., Ritz, J.-F. 2016: The Dinaric fault system: Large-scale structure, rates of slip, and Plio-Pleistocene evolution of the transpressive northeastern boundary of the Adria microplate. Tectonics 35-10. DOI:

Placer, L. 1971: Nekaj osnovnih podatkov o idrijskem prelomu. Idrijski razgledi 16-1.

Placer, L. 1982: Tektonski razvoj idrijskega rudišča. Geologija 25-1.

Placer, L., Koler, B. 2007: Predlog geodetske spremljave aktivnih prelomnih con. Geologija 50-2.

Placer, L., Vrabec, M., Celarc, B. 2010: The bases for understanding of the NW Dinarides and Istria Peninsula tectonics. Geologija 53-1. DOI:

Rižnar, I., Koler, B., Bavec, M. 2007: Recent activity of the regional geologic structures in western Slovenia. Geologija 50-1. DOI:

Serpelloni, E., Vannucci G., Anderlini, L., Bennett, R. A. 2016: Kinematics, seismotectonics and seismic potential of the eastern sector of the European Alps from GPS and seismic deformation data. Tectonophysics 688. DOI:

Stemberk, J., Košťák, B., Vilimek, V. 2003: 3D monitoring of active tectonic structures. Journal of Geodynamics 36, 1-2. DOI:

Stemberk, J., Košťák, B., Cacoń, S. 2010: A tectonic pressure pulse and geodynamic activity recorded from long-term monitoring of faults in Europe. Tectonophysics 487. DOI:

Šebela, S., Gosar, A., Košťák, B., Stemberk, J. 2005: Active tectonic structures in the W part of Slovenia - setting of micro-deformation monitoring net. Acta Geodynamica et Geomaterialia 2-1.

Šebela, S., Turk, J., Mulec, J., Košťák, B., Stemberk, J. 2009: Statistical evaluation of the 3D monitoring of displacements of Dinaric Fault Zone in Postojna Cave, Slovenia. Acta Geodynamica et Geomaterialia 6-2.

Twiss, R. J., Moores, E. M. 1992: Structural geology. New York.

Vičič, B., Aoudia, A., Javed, F., Foroutan, M., Costa, G. 2019: Geometry and mechanics of the active fault system in western Slovenia. Geophysical Journal International 217-3. DOI:

Vrabec, M. 2012: Evidence of Quaternary faulting in the Idrija fault zone, Učja canyon, NW Slovenia. RMZ – Materials and Geoenvironment 59, 2-3.

Vrabec, M., Preuner, P., Zupan Hajna, N., Mihevc, A., Bosak, P. 2018: Neotectonic vertical-axis rotations in the Adria-Eurasia collision zone reviled from Paleomagnetic data of Pliocene-Quaternary cave sediments (Slovenia). INQUA SEQS Quaternary Stratigraphy in Karst and Cave Sediments, Program, Abstract and Guide Book. Postojna.

Weber, J., Vrabec, M., Pavlovčič-Prešeren, P., Dixon, T., Jiang, Y., Stopar, B. 2010: GPS-derived motion of the Adriatic microplate from Istria Peninsula and Po plain, and geodynamic implications. Tectonophysics 483, 3-4. DOI:

Žibret, G., Komac, M., Jemec Auflič, M. 2012: PSInSAR displacements related to soil creep and rainfall intensities in the Alpine foreland of western Slovenia. Geomorphology 175-176. DOI:

Žibret, L., Žibret, G. 2014: Use of geomorphological indicators for the detection of active faults in southern part of Ljubljana moor, Slovenia. Acta geographica Slovenica 54-2. DOI:

Živčić, M., Čarman, M., Gosar, A., Jesenko, T., Zupančič, P. 2011: Potresi ob Idrijskem prelomu. Idrijski razgledi 56-1.

How to Cite
Gosar A. Measurements of tectonic micro-displacements within the Idrija fault zone in the Učja valley (W Slovenia). AGS [Internet]. 2020May26 [cited 2020Jul.10];60(1):79–93. Available from: