Earth surface response to Quaternary faulting and shallow crustal structure in the eastern Adria-Alpine collision zone and the Friulian plain

• Applicants: Professor Dr. Friedhelm von Blanckenburg; Dr. Christoph Grützner; Professor Dr. Klaus Reicherter
• Subject Area: Geophysics ; Geodesy, Photogrammetry, Remote Sensing, Geoinformatics, Cartography
• Term: from 2017 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 365171455

• Final Report Year: 2020

Final Report Abstract

In our project we wanted to better understand the active tectonics of the Alpine-Dinarides transition zone. Important research questions were: • Which faults are active and what is their Late Quaternary seismic history? • What is the length of their earthquake recurrence intervals and what are the maximum magnitudes? • How do seismically active faults affect catchment-averaged erosion rates? • Can we use erosion rates to identify regions of active tectonics where little is known about actual faults? We conducted geomorphological analyses based on high-resolution elevation data, geophysical surveys, and paleoseismological trenching to understand the activity of faults in W Slovenia and NE Italy. In a paleoseismological trench across the Predjama Fault we found at least one earthquake with a minimum magnitude of MW6.1 that occurred between 13 - 0.7 ka, very likely not earlier than 8.4 ka. At the Idrija Fault, a surface-rupturing earthquake with a magnitude of at least MW6.1 happened in the last ~2.1 ka. This event could correspond to the 1511 Idrija earthquake. At the Selce Fault, a paleoseismological trench showed evidence for Late Quaternary strike-slip motion. The Udine-Buttrio Thrust in Italy uplifts young river terraces of the Natisone River along a splay fault in addition to ongoing uplift along its main fault trace. Additional evidence for active faulting was found along the Sava Fault and on faults on the karst plateau south of Jesenice. Our results show that the faults rupture in rare, but strong earthquakes, which dominate the seismic moment release. We show that instrumental and historical seismicity data do not capture the strongest events in this area. The fact that many of the SW-NE trending, parallel faults are active implies that the deformation in western Slovenia is distributed, rather than focussed on one major structure. Our work on the catchment-averaged denudation rates revealed an interesting pattern. Although the study area was not glaciated, we found erosion rates that are much higher than those in other nonglaciated Alpine regions such as the Koralpe. We have shown that cosmogenic Be records the catchment-wide denudation response to strike-slip faulting. A first combined analysis of the observed erosion rates with geomorphic features indicate that slip rates along the three different main faults sampled must be relatively low. With our erosion project we present a successful proof of concept that cosmogenic Be-derived denudation rates record the erosional response to tectonic movement also in strike-slip dominated environments. This is a novel result, which shows that this tool can be by applied to other strike-slip environments worldwide. Ostthüringer Zeitung, 2017-07-13: https://www.otz.de/regionen/jena/jenaer-geowissenschaftler-graben-alte-erdbebenspuren-inslowenien-aus-id222982995.html Science show on Slovenian TV channel RTV4. 2018-11-22: https://4d.rtvslo.si/arhiv/ugriznimo-znanost/174577547

Publications

• (2018). Active faulting in NW Slovenia and NE Italy – first results from field studies and tectonic geomorphology. 9th International INQUA Meeting on Paleoseismology, Active Tectonics and Archaeoseismology (PATA), Possidi, Greece, 25–27 June, 2018, 91-94
  Grützner, C.
  
• (2018). Active faulting in the eastern Southern Alps-Dinarides – insights from field studies, geophysics, and high-resolution topography data. GeoBonn 2018, Annual DGGV Meeting, Bonn, Germany, 02-06 September, 2018
  Grützner, C.
  
• (2018). The geomorphological imprint of active faulting in NW Slovenia and NE Italy – first results from field studies and high-resolution topography data. 17th TSK meeting, Jena, Germany, 19-25 March, 2018
  Grützner, C.
  
• (2019). Active tectonics of the Dinarides in Slovenia - new insights from palaeoseismology. INQUA Congress, Dublin, Ireland, 25-31 July, 2019
  Grützner, C., Aschenbrenner, S., Jamšek Rupnik, P., Krämer, A., Saifelislam, N., Ustaszewski, K., Vičič, B., Viscolani, A., Vrabec, M., Welte, J., Reicherter, K.
  
• (2019). Active tectonics of the Dinarides in Slovenia-new data from remote sensing, field studies, geophysics, and palaeoseismology. EGU2019, Vienna, Austria, 07-12 April, 2019, Geophysical Research Abstracts 21, 11300
  Grützner, C., Aschenbrenner, S., Jamšek Rupnik, P. J., Ustaszewski, K., Vičič, B., Vrabec, M., Welte, J., & Reicherter, K.
  
• (2019). Paleoseismology in continental interiors and seismic hazard assessments - what have we learned? GeoMünster 2019, Annual DGGV Meeting, Münster, Germany, 22-25 September, 2019
  Grützner, C.
  
• (2020). Active faulting in SW Slovenia - the Selce Fault. GeoUtrecht 2020, Annual DGGV Meeting, virtual, 21-26 August, 2020
  Grützner, C., Diercks, M., Tsukamoto, S., & Ustaszewski, K.