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In tectonically active mountain ranges, the landscape is shaped by the interplay of erosion/sedimentation and tectonically driven crustal deformation. Characteristic landforms such as moraines, wind gaps, fault scarps, and river terraces can be used to decipher the landscape evolution. However, the available data often allow for different interpretations. Here we study the Pradol (Pradolino) Valley in Western Slovenia, a deeply incised canyon whose floor rests several hundreds of metres above the surrounding valleys. We use high-resolution digital elevation models, geomorphic indices and field observations to unravel the evolution of this peculiar landform. We present a six-stage evolution model of the canyon that includes the blockage of valleys by advancing glaciers, river diversion, and rapid incision due to a high discharge of post-glacial meltwater. The formation of the Pradol Valley was most likely facilitated by an underlying fault that serves as an easily erodible weakness zone in the Mesozoic limestones. Our model indicates that the formation of the canyon could have occurred during the last glaciation, which results in incision rates of several cm/yr. With the proposed model we can explain all remote and field observations available. Our study shows that a complex interplay of different landscape-shaping processes is needed to explain the occurrence of the Pradol dry valley and that rapid changes in the morphology occurred after the last glacial maximum. [ABSTRACT FROM AUTHOR]

Remote sensing-based tectonic geomorphology is widely applied to study neotectonic processes. This technique is relatively cheap and easy to apply, and it allows investigating large areas for tectonic activity. Existing literature comprises a variety of indices and techniques, seemingly able to work in almost all tectonic settings. In this paper we study a particularly challenging region in W Slovenia and NE Italy, characterised by slow deformation rates, high precipitation, dense vegetation, and intense modification of the landscape and drainage system due to karst processes. We apply a suite of well-established geomorphic indices including terrain ruggedness, surface roughness, hypsometric integral and analyses of drainage parameters, as well as several less commonly applied analyses, such as the assessment of doline density and doline geometry. The aim was to test the capabilities of the applied techniques at various spatial scales and to extract information about the active tectonics. We begin with broad, regional analyses to detect the morphological imprint of active faults in the landscape. Then, we perform detailed studies of selected sites and single faults. Finally, we analyse a polje located on the trace of an active fault in the highest detail. We then compare the different techniques and different digital elevation models regarding their usefulness for detecting tectonic influences on the karstic landscape. The results show that most of the well-established methods we tested are not suitable to detect even the largest, clearly active faults in the area. The resolution of the used DEMs also has a notable impact on the analyses. We conclude that it is almost impossible to identify active faults solely based on the used techniques. This is mainly due to the low deformation rates and to the intense karstification of the study area that leads to a disconnected surface drainage system. Additional problems arise from the strike-slip mechanism of active faulting. Lithological contrasts and inactive dip-slip faults can lead to false-positive signals of tectonic activity. However, some of our results also show a tectonic signal, indicating neotectonic strike-slip deformation with a notable dip-slip component. Remote sensing studies have demonstrated to be powerful tools for tectonic geomorphology studies, but low tectonic rate karstic landscape conditions as in W Slovenia/NE Italy push even the most trusted methods to their limits and highlight the importance of validation and ground-checks of the results. • Tests quantitative geomorphologic metrics to a challenging karstic study area • Investigates different spatial scales: regional, local fault traces, single polje • Lithology and karst control landscape, with metrics failing to detect active faults • Metrics less sensitive to fault activity than faulting mechanism • Using metrics to inform on active tectonics can fail in slow deforming karst areas [ABSTRACT FROM AUTHOR]

The Bolivian Amazon foreland basin is controlled by i) the sediment input from the Andes and the topographic load; ii) the basinal uplift in the forebulge; and iii) the uplifting Fitzcarrald Arch in the north. These boundary conditions should lead to bending and active faulting of the crust. However, although the presence of active faults has been inferred from geomorphological studies, neither seismicity studies nor geodetic methods and geomorphological constraints have been successful in identifying active faults so far. Reasons for this are mainly the dense vegetation and the extremely dynamic fluvial landscape of the Bolivian Amazon. In this study we use the TanDEM-X and SRTM digital elevation models to show that there are at least five faults, several tens of kilometres long, that are active. We present offset measurements from fault scarps and combine these data with river system analyses. Our results suggest that tilting of tectonic blocks occurred in the Late Pleistocene or Holocene. The reversal of fluvial longitudinal profiles and incipient creek erosion inside paleochannels, markers of young tectonic activity, allow us to reconstruct the tilting directions. We find two orthogonal main faulting directions: WNW-ESE trending faults parallel to the Andean uplift and NNE-SSW trending faults tangent to the bulge of the uplifting Fitzcarrald Arch. Thus, our study area records the interplay between these two main drivers of crustal deformation. We show that some fault scarps were caused by large single earthquakes with magnitudes of around M W 7, while others have recorded multiple strong seismic events. These magnitudes exceed by far the magnitudes known from instrumental seismicity in the last 40 years. Our results shed light on the seismic hazard of the region and highlight that catastrophic river course changes due to sudden uplift in this low-relief region are an underestimated hazard. • We have identified four previously unknown active faults in the Bolivian Amazon. • These faults suggest that here neotectonics are driven by the interplay between the forebulge and the Fitzcarrald Arch. • Faults and tilting blocks control the evolution of the fluvial landscape of the Bolivian Amazon. • Seismic risk in the Bolivian Amazon is higher than previously thought. [ABSTRACT FROM AUTHOR]

The NW-SE trending Udine-Buttrio Thrust is a partly blind fault that affects the Friulian plain southeast of Udine in NE Italy. It is part of a wider fault system that accommodates the northward motion of the Adriatic plate. Although seismic reflection data and morphological evidence show that the fault was active during the Quaternary, comparably little is known about its tectonic activity. We used high-resolution digital elevation models to investigate the surface expression of the fault. Measured vertical surface offsets show significant changes along strike with uplift rates varying between 0 and 0.5 mm/yr. We then analyze a topographic scarp near the village of Manzano in more detail. Field mapping and geophysical prospections (Georadar and Electrical Resistivity Tomography) were used to image the subsurface geometry of the fault. We found vertical offsets of 1–3 m in Natisone River terraces younger than 20 ka. The geophysical data allowed the identification of deformation of the fluvial sediments, supporting the idea that the topographic scarp is a tectonic feature and that the terraces have been uplifted systematically over time. Our findings fit the long-term behaviour of the Udine-Buttrio Thrust. We estimate a post-glacial vertical uplift rate of 0.08–0.17 mm/yr recorded by the offset terraces. Our results shed light on the Late Quaternary behaviour of this thrust fault in the complicated regional tectonic setting and inform about its hitherto overlooked possible seismic hazard. [ABSTRACT FROM AUTHOR]

The northward motion of the Adriatic plate with respect to the Alps leads to thrusting on E-W striking fault in NE Italy and to right-lateral strike-slip faulting on NW-SE trending Dinaric structures in W Slovenia. GPS data allow to understand the collision on a regional scale, but the networks are either not dense enough to draw conclusions on the activity of individual faults, or displacement rates across these faults are below GPS resolution. Instrumental seismicity in the Alpine-Dinarides transition zone is higher than elsewhere in the Alps. However, only few reliable moment tensor solutions of moderate to strong earthquakes depict the slip vectors and the geometry of single faults, and the background seismicity >M3 is rather diffuse. Strong historical earthquakes with magnitudes exceeding M6 are documented in our study area, but in most cases they cannot be tied to the fault that ruptured. Published paleoseismic evidence for surface-rupturing earthquakes is very limited, but geomorphological studies have shown that a number of thrust faults in NE Italy and strike-slip faults W Slovenia have been active in the Quaternary. So far there is little data on slip rates of individual faults, on their earthquake history and recurrence intervals, and on their seismic potential. It is not clear if crustal deformation is distributed across many active structures or if few main faults take up most of the deformation. The transition between head-on thrusting in N Italy and right-lateral motion on NW-trending faults in Slovenia needs further research.In this study we used remote sensing, field studies, near-surface geophysics, and palaeoseismology to better understand crustal deformation as a response to the Adria-Alpine convergence. We focussed on the right-lateral strike-slip faults in W Slovenia. High-resolution digital elevation models from LiDAR and drones allowed us to image geomorphological evidence of active tectonics and potentially surface-rupturing earthquakes in the Late Quaternary. The widespread karst made it difficult to apply classical techniques of tectonic geomorphology, which mainly use landscape features shaped by surface drainage and the associated sedimentation and erosion. However, the high-resolution data proved to be useful in identifying offset and deformed marker surfaces. Field mapping and structural data helped to trace the active faults and to determine their sense of motion. Near-surface geophysics were applied to image the shallowest parts of several faults and to identify deformation in young geological units. Based on these data we excavated paleoseismological trenches to date paleo-earthquakes.Our results show that a number of roughly parallel, NW-SE trending strike-slip faults in Slovenia have been active in the Late Quaternary. Crustal deformation appears to be not taken up by one or two main structures only, but rather distributed in a wide shear zone and across many faults. This is in contrast to the Alpine front further west in NE Italy, where deformation is rather localised on S-vergent thrusts along the front of the Southern Alps. Given the low rate of overall deformation, the distributed faulting results in low fault slip-rates and large recurrence intervals of strong and even surface-rupturing earthquakes. [ABSTRACT FROM AUTHOR]