Active tectonics


Active tectonics
| Tue, 13 Sep, 09:40–10:40|Montanistika Building

Orals: Tue, 13 Sep | Montanistika Building

Chairperson: Christoph Grützner
Ana Mladenovic

Since the Late Cretaceous, after closure of the Neotethys ocean, tectonic processes in the central Balkan Peninsula were mainly controlled by the mutual interaction of the Adriatic and the Eurasian plates, and tectonic units in-between. Most of the tectonic structures that have been active during Cenozoic times were inherited from previous tectonic stages under different tectonic regimes. Tectonic activity within the Carpatho-Balkan orogen in eastern Serbia since Miocene is conditioned by the existence of the rigid Moesian promontory eastern of the research area, which limited thrusting of the Carpatho-Balkan units. Rather than that, further compression and complex rotations around the Moesian promontory have been accommodated by the formation of the large strike-slip fault systems (e.g. Cerna-Jiu fault, Timok fault), that accommodated up to 100 km of cumulative displacement. According to earthquake focal mechanisms, faults belonging to these fault systems are still active.

In this abstract, we present results about youngest and recently active faults in the area of the Carpatho-Balkanides in eastern Serbia, based on the studies of fault kinematics, seismicity and earthquake focal mechanisms, as well as tectonic geomorphological studies in karst caves.

Results show that the research area is primarily characterized by strike-slip tectonics, which most likely results from far-field stress generated by the Adria-push mechanism. However, such stress field showed to be highly heterogeneous, where local areas of transtension and transpression have also been important in controlling the recent fault kinematics in this part of the Carpatho-Balkanides.

How to cite: Mladenovic, A.: How active is recent tectonics in the central Balkans: Evidence from the Serbian Carpatho-Balkanides, 15th Emile Argand Conference on Alpine Geological Studies, Ljubljana, Slovenia, 12–14 Sep 2022, alpshop2022-62, https://doi.org/10.5194/egusphere-alpshop2022-62, 2022.

Miklos Kazmer and Krzysztof Gaidzik

Most of the Periadriatic Fault System have been active during Oligocene and Miocene times. Its western part seems to be inactive ever since, while the Lavanttal and Sava faults in the east show limited seismic activity. We conducted a systematic archaeoseismological survey along the Periadriatic-Sava fault system, assessing buildings and archaeological sites for earthquake damage. Eight sites, four Roman and four Medieval, display evidence for destructive earthquakes during the past 2000 years. These are San Candido (Medieval) and Lienz (Medieval) on the Pustertal fault, Teurnia (Roman) and Millstatt (Medieval) on the Mölltal fault, Arnoldstein (Medieval) and Magdalensberg (Roman) just north of the Karavanka fault, Roman Celeia (Celje) at the Savinja / Sava faults, and Roman Siscia (Sisak) nearby the Sava fault. Damaged upright walls of Medieval buildings and deformed floors of Roman settlements testify to local intensity up to IX. Ongoing studies of archaeological stratigraphy and construction history allow dating of one or more seismic events at each site, ranging from the 1st century AD to the 17th century. We would be cautious about pointing out epicentres at this moment. However, it is remarkable that sites, 70 km apart in average, along a a 380 km long segment of an ‘inactive’ fault zone carry evidence for so many high-intensity destructive events.

How to cite: Kazmer, M. and Gaidzik, K.: Seismic activity along the Periadriatic and Sava Faults in the past two millennia – an archaeoseismological assessment, 15th Emile Argand Conference on Alpine Geological Studies, Ljubljana, Slovenia, 12–14 Sep 2022, alpshop2022-35, https://doi.org/10.5194/egusphere-alpshop2022-35, 2022.

Christian Sue, Andrea Walpersdorf, Dorian Bienveignant, Lina Al Najjar, Estelle Hannouz, Anne Lemoine, and Stephane Baize

The Western Alps current tectonics is characterized by seismically active radial extension in the core of the belt, combined with transcurrent to transpressive tectonics in its external zone and foreland associated with a moderate seismicity. We focus on the tectonic transfer from the W-Alps to their foreland, namely the French Rhône Valley, a region with high societal challenges, including demography, nuclear powerplants, and chemical industries. We combine seismotectonic and geodetic (GNSS) approaches to constrain the stress and strain fields of the area extended from the alpine External Crystalline Massifs to the eastern edge of the French Massif Central, which encompasses the Rhône Valley. Seismic strain rates for a set of subareas defined on tectonic arguments (seismotectonic zoning) have been evaluated. They are processed by combining the total seismic energy obtained with statistical integrations of Gutenberg-Richter distributions with representative focal-mechanisms obtained from stress inversions. Seismic strain rates are then compared to the geodetic strain field obtained from an updated GNSS solution focused on the study area. Seismic strain rates of subareas in the Rhone Valley and surroundings range between a few nanostrains/yr and 10E-2 nanostrains/yr. In terms of amplitude, geodesy seems to provide deformation rates one order of magnitude higher than seismicity. However, our seismic strain tensors are globally consistent with the geodetic ones, specifically in the front of the Alps (Belledonne region), where seismic and geodetic networks are denser. In a last step, we replace these strain and stress fields in a new 3D-structural model, which has been developed on purpose. It integrates the main crustal units and the main faults of the area, allowing to better constrain the relationship between the current deformation and stress patterns of the Rhône Valley under the Alpine influence, and the inherited fault system carving the entire domain.

How to cite: Sue, C., Walpersdorf, A., Bienveignant, D., Al Najjar, L., Hannouz, E., Lemoine, A., and Baize, S.: Tectonic Transfer from the Western Alpine Front to the French Rhône Valley in its 3D-Structural Context, 15th Emile Argand Conference on Alpine Geological Studies, Ljubljana, Slovenia, 12–14 Sep 2022, alpshop2022-20, https://doi.org/10.5194/egusphere-alpshop2022-20, 2022.