EGU23-5228, updated on 11 Aug 2023
https://doi.org/10.5194/egusphere-egu23-5228
EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Identification of faulted geomorphic markers and slip-rate estimation along the source of the 2020 Mw6.4 Petrinja earthquake (Croatia), the Petrinja-Pokupsko Fault.

Lucilla Benedetti1, Maxime Henriquet1, Stéphane Baize2, Branko Kordic3, Adrien Moulin4, Josipa Maslač3, Nikola Belić3, Francesca Cinti5, Daniela Pantosti5, Stefano Pucci5, Riccardo Civico5, Alessio Testa6, Paolo Boncio6, Bruno Pace6, Petra Jamšek Rupnik7, Cecile Lasserre8, and Marianne Metois8
Lucilla Benedetti et al.
  • 1CEREGE - CNRS, Aix en Provence, France (benedetti@cerege.fr)
  • 2IRSN, Fontenay-aux-Roses, France
  • 3Croatian Geological Survey (HGI-CGS), Milana Sachsa 2, 10000 Zagreb, Croatia
  • 4King Abdullah University of Science and Technology, Thuwal, Saudi Arabia
  • 5Istituto Nazionale di Geofisica e Vulcanologia, Sezione Sismologia e Tettonofisica
  • 6Università G. d'Annunzio Chieti - Pescara
  • 7Geological Survey of Slovenia, Ljubljana, Slovenia
  • 8Université Claude Bernard Lyon 1, Laboratoire de Géologie de Lyon

Europe has experienced over the last years earthquakes of moderate magnitude (Mw 5-6), yet destructive, reminding us of the seismogenic potential of slowly deforming regions. Among them, the 2020 Mw 6.4 Petrinja earthquake ruptured the Petrinja-Pokupsko Fault (PPKF) in Central Croatia, about 50-km southeast of Zagreb, a region in which the caracterisation of seismogenic faults had been insufficiently studied before that event. Understanding the strain accommodation through time and space is critical for accurate assessment of the regional seismic hazard.

Using field observations and high-resolution topographical data derived from airborne LiDAR (~10 cm resolution) and tri-stereo satellite images (Pléiades, resolution 50 cm), we accurately mapped the fault trace, underlined at several sites by geomorphic markers such as valleys, terrace risers, and alluvial fans that have recorded cumulative displacements ranging from 5 to > 50 m and potentially up to ~180 m. Along the studied section, our fault mapping is composed of a clear NW-SE-trending 10-km-long strand between Donja and Cepelis, and of 1-4-km-long right-stepping segments marked by a non-negligible vertical component. The southern strand is composed of 2-3 sub-parallel segments that accommodate the deformation within a < 500 m wide fault zone.

We have identified several sites on the main southern strand where offsets have been accurately measured and where displaced markers have been sampled for cosmogenic nuclide exposure dating and radiocarbon datings. This will allow to estimate the slip-rate for this fault at different sites and over several time spans.

The mapped fault appears very discontinuous with the deformation absorbed by a series of small fault sections rather than on a single fault strand. This likely reflects a recent transpressive deformation, with immature faults,  in agreement with the source parameter of the 2020 Petrinja earthquake derived from seismology.

Finaly, the 2020 coseismic surface ruptures affected the northern section of the PPKF, while the mapped cumulative displacements appears more prominent along the southern section. A better knowledge of the seismic history of this entire fault system is thus crucial for seismic hazard assessment of this area.

How to cite: Benedetti, L., Henriquet, M., Baize, S., Kordic, B., Moulin, A., Maslač, J., Belić, N., Cinti, F., Pantosti, D., Pucci, S., Civico, R., Testa, A., Boncio, P., Pace, B., Jamšek Rupnik, P., Lasserre, C., and Metois, M.: Identification of faulted geomorphic markers and slip-rate estimation along the source of the 2020 Mw6.4 Petrinja earthquake (Croatia), the Petrinja-Pokupsko Fault., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5228, https://doi.org/10.5194/egusphere-egu23-5228, 2023.