We applied an interdisciplinary approach to analyze the late Quaternary activity of the Sava Fault in the Slovenian Southern Alps. The Sava Fault is an active strike-slip fault, and part of the ...Periadriatic Fault System that accommodated the convergence of Adria and Europe. It is one of the longest faults in the Southern Alps. Using high-resolution digital elevation models from lidar and photogrammetric surveys, we were able to overcome the challenges of assessing fault activity in a region with intense surface processes, dense vegetation, and relatively low fault slip rates. By integrating remote sensing analysis, geomorphological mapping, structural geological investigations, and near-surface geophysics (electrical resistivity tomography and ground penetrating radar), we were able to find subtle geomorphological indicators, detect near-surface deformation, and show distributed surface deformation and a complex fault pattern. Using optically stimulated luminescence dating, we tentatively estimated a slip rate of 1.8 ± 0.4 mm/a for the last 27 ka, which exceeds previous estimates and suggests temporal variability in fault behavior. Our study highlights the importance of modern high-resolution remote sensing techniques and interdisciplinary approaches in detecting tectonic deformation in relatively low-strain rate environments with intense surface processes. We show that slip rates can vary significantly depending on the studied time window. This is a critical piece of information since slip rates are a key input parameter for seismic hazard studies.
Located at the northeastern corner of the Adria microplate, the Alps‐Dinarides junction represents a key region for understanding how the Adria microplate interacts with stable Europe. However, ...little is known on how the present‐day deformation imposed by the rotation of the Adria microplate is absorbed across the Dinarides. Using morphotectonic analysis based on satellite and aerial images, accurate topographical maps, and digital elevation models combined with field investigations, we mapped in detail the three main active faults of the Northern Dinarides. Geomorphic and geological cumulative displacements ranging from a few meters to several kilometers have been identified on those faults and dated for the most recent ones using 36Cl exposure dating. Those results yielded a total right‐lateral motion of 3.8 ± 0.7 mm/yr oriented N317. Comparing our results with the motion expected from Adria rotation models suggests that the Northern Dinarides absorbs most of the predicted Adria‐Eurasia motion, thus representing the eastern boundary of the microplate. However, a significant E‐W component is lacking, suggesting that part of the stress imposed by the microplate rotation is transferred farther to the east. Finally, bounds placed on the Plio‐Pleistocene kinematics confirm that faulting onset occurred during the Early Pliocene and evidence a significant kinematic change at the Early/Middle Pleistocene boundary.
Key Points
Pleistocene slip rates of the Dinaric faults are derived from displaced markers and 36Cl CRE ages
Chronological bounds are placed on the kinematic evolution of the Dinarides over the Plio‐Pleistocene
Deformation in the Dinarides absorbs most of the Adria microplate rotation (versus stable Eurasia)
Deciphering deformation mechanisms within Quaternary sediments in a highly dynamic environment such as the southeast European Alps is often a challenging task that requires the use of a variety of ...methods. Due to the geohazards involved, the interpretation of deformation mechanisms can have a major impact on society and may enable the preparation of appropriate engineering solutions. We present an example of how deformation structures can be studied by integrating geomorphological, sedimentological and structural geological mapping using photogrammetric and leveling surveys, paleoseismological techniques, optically stimulated luminescence dating and ground penetrating radar surveys. Quaternary deposits on the slopes of the formerly glaciated Soča Valley near Most na Soči are tilted and dissected along numerous faults within the deformation zone of the Idrija Fault, a large, active, dextral strike-slip fault. Reconstruction of deformation history indicates that at least five deformation events occurred during deposition of the glaciofluvial succession interbedded with glaciolacustrine deposits, dated to Penultimate Glaciation. Ground penetrating radar profiles and outcrop observations reveal NE – SW striking faults, which are approximately perpendicular to the primary Idrija Fault. Based on the local geologic setting, we considered glaciotectonics, gravitational faulting due to ice-decay collapse or slope instability, and tectonic faulting as possible deformation mechanisms. Based on detailed documentation and analysis of the geometry and kinematics of the deformations, we interpret the observed deformations as secondary structures that result from paleoseismic activity of the Idrija Fault, and some structures resulting from glaciotectonics and gravitational faulting. The transtensional type of deformations at the studied site shows the local character of the main fault, which occurs here due to geometrical and kinematical changes of the Idrija Fault causing local transtension in the Most na Soči area. The complexity of the fault and the first paleoseismic evidence dating back to Penultimate Glaciation provide valuable new data for understanding the seismic hazard in the region.
•Origin of deformations within Quaternary sediments in a highly dynamic environment unraveled.•Glaciofluvial and glaciolacustrine deposits record recurrent faulting and non-tectonic deformations.•First paleoseismological evidence on the major Idrija Fault extending back to Penultimate Glaciation.•Local scale fault complexities reflect fault geometric and kinematic changes.
The earthquake (Mw 6 from the SHEEC defined by the MDPs) that occurred in the central part of Slovenia on 14 April, 1895, affected a broad region, causing deaths, injuries, and destruction. This ...event was much studied but not fully explained; in particular, its causative source model is still debated. The aim of this work is to contribute to the identification of the seismogenic source of this destructive event, calculating peak ground velocity values through the use of different ground motion prediction equations (GMPEs) and computing a series of ground motion scenarios based on the result of an inversion work proposed by Jukić in 2009 and on various fault models in the surroundings of Ljubljana: Vič, Želimlje, Borovnica, Vodice, Ortnek, Mišjedolski, and Dobrepolje faults. The synthetic seismograms, at the basis of our computations, are calculated using the multi-modal summation technique and a kinematic approach for extended sources, with a maximum peak ground velocity value of 1 Hz. The qualitative and quantitative comparison of these simulations with the macroseismic intensity database allows us to discriminate between various sources and configurations. The quantitative validation of the seismic source is done using ad hoc ground motion to intensity conversion equations (GMICEs), expressly calculated for this study. This study allows us to identify the most probable causative source model of this event, contributing to the improvement of the seismotectonic knowledge of this region. The candidate fault that has the lowest values of average differences between observed and calculated intensities and chi-squared is a strike slip fault with a toward-north rupture as the Ortnek fault.
ABSTRACT
In this study, we focused on the Pliocene–Early Pleistocene fluvial terraces in the Velenje Basin and reconstructed the morphostratigraphy, sedimentary depositional environment, provenance ...and age of the gravel deposits using geomorphological, sedimentological, petrographic and chronological analyses. Geomorphological mapping revealed the presence of two main river‐terrace groups. The terraces in the older terrace group are severely degraded and preserved only as remnants capping high ground, while in contrast the younger group is better preserved. Detailed lithofacies analyses of four selected stratigraphic sections of the older terrace group show that the gravel was deposited in a meandering and wandering environment. The gravel consists of metamorphic, igneous, volcaniclastic, clastic and carbonate lithologies derived from the north, east and west from the Paka River catchments. To determine the timing of deposition, we performed isochron‐burial dating using cosmogenic 26Al and 10Be. Our new age constraints date the deposition of the older terrace group to 2.7 ± 0.3 Ma. Establishing the aggradation and incision model of the Velenje Basin documents pronounced regional tectonic uplift during the Pliocene–Early Pleistocene, which led to incision and the subsequent formation of a terrace staircase.
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