Predictive Modelling of Landslide Susceptibility in the Western Carpathian Flysch Zone

Landslides are the most common geodynamic phenomenon in Slovakia, and the most affected area is the northwestern part of the Kysuca River Basin, in the Western Carpathian flysch zone. In this paper, we evaluate the susceptibility of this region to landslides using logistic regression and random forest models. We selected 15 landslide conditioning factors as potential predictors of a dependent variable (landslide susceptibility). Classes of factors with too detailed divisions were reclassified into more general classes based on similarities of their characteristics. Association between the conditioning factors was measured by Cramer’s V and Spearman’s rank correlation coefficients. Models were trained on two types of datasets—balanced and stratified, and both their classification performance and probability calibration were evaluated using, among others, area under ROC curve (AUC), accuracy (Acc), and Brier score (BS) using 5-fold cross-validation. The random forest model outperformed the logistic regression model in all considered measures and achieved very good results on validation datasets with average values of AUCval=0.967, Accval=0.928, and BSval=0.079. The logistic regression model results also indicate the importance of assessing the calibration of predicted probabilities in landslide susceptibility modelling.

Tracing Pre-Mesozoic Tectonic Sutures in the Crystalline Basement of the Protocarpathians: Evidence from the Exotic Blocks from Subsilesian Nappe, Outer Western Carpathians, Poland

Pre-Mesozoic exotic crystalline blocks within the Outer Carpathian flysch have potential to unravel the nature of their eroded basement source(s) and to reconstruct the Paleozoic–Precambrian history of the Protocarpathians. Strongly tectonized Campanian–Maastrichtian grey marls in the Subsilesian Nappe of the Outer Western Carpathians in Poland contain a variety of different lithology types, including granitoids and andesites. Petrological investigations coupled with zircon and apatite U-Pb dating were performed on crystalline (subvolcanic) exotic blocks from a locality in the Subsilesian Nappe. U-Pb zircon dating yields magmatic crystallization ages of c. 293 Ma for the microgranitoid and c. 310 Ma for the andesite block, with inherited zircon cores yielding Archean, Paleoproterozoic, Mesoproterozoic and Cadomian ages. Whole rock trace element and Nd isotope data imply that the melt source was composed of a significant Neoproterozoic crustal component in both the microgranite and andesite. The Late Carboniferous–Permian magmatic activity likely continues outside the Carpathian Belt and can be linked to a Late Paleozoic transtensional zone, which is a continuation of the Lubliniec–Kraków Zone that extends under the Carpathians to Moesia. This Late Paleozoic transtensional zone was probably reactivated during the Late Cretaceous under a transpressional regime within the Żegocina tectonic zone, which caused the uplift of the Subsilesian Ridge and intensive erosion.

Stabilization of Landslides Sliding Layer Using Electrokinetic Phenomena and Vacuum Treatment

The article presents the efficiency of application of cohesive soil dewatering for increasing its resistance to shearing, which influences the mass stability of flysch rock. Studies of the typical soil constituting the contact layer initiating the sliding of existing Carpathian flysch landslides were conducted. This aspect was examined because the water content of this soil decides its ability to form a sliding surface of the landslide block soil. The soil was subjected to changes in water content by dewatering with different methods. The influence of dewatering by self-acting gravitational outflow was examined and was additionally aided by two selected methods: electrokinetic phenomena and vacuum treatment. The model study conducted demonstrates the influence of the abovementioned dewatering methods on increasing the strength parameter of the soil at the contact layer in which sliding surfaces can be created. The paper also demonstrates the degree to which the application of the vacuum and electrokinetic treatment caused by DC current voltage influences the draining, decrease of plasticity, and increase of soil shear stress resistance. The application conditions and increase in effectiveness due to the application of the studied methods were determined. The proposed methods allowed for the strengthening of slopes for two exemplary landslides which formed in the area of occurrence of the Carpathian flysch.

Real time and in-situ analysis of the gas-emissions of the Eastern Carpathians: results and perspectives

<p>The Carpathian-Pannonian region was dominated by diverse volcanic activity for the last 20 million years, and even 1 million years ago there was precedent for active zones.  Although volcanic eruptions are very uncommon in the region today, however the frequent earthquakes in the Carpathian-bend, the numerous appearance and intense manifestation of gas-emissions in the southeastern areas of the region and many petrochemical and geochemical volcanologic studies as well, indicate that the area is likely not completely inactive. The gas emissions investigated by us may be directly related to these geodynamic processes [1].</p><p>In Romania, the Eastern Carpathian Neogene-Quaternary volcanic chain and it’s neighbouring zones contain most of the carbon dioxide rich gas emissions, which also occur in the form of natural mofettes, bubbling pools and springs. They can appear in frequently populated settlements more often in cellars, which puts the inhabitants in direct danger due the lack of information in the public knowledge.</p><p>The motivation of our work is to gather real time and in-situ information with the help of Multi-Gas instrument about the composition of the gas-emissions across the Eastern Carpathians and to create a high resolution geological map from the measured sites in the mentioned area above. Furthermore, we would like to clarify if there is any relation between the tectonic characteristics of the study area and the manifestation, concentration of gas-emissions.</p><p>In total, 205 gas emissions were investigated for their CO<sub>2 </sub>(0-100%), CH<sub>4 </sub>(0-7%) and H<sub>2</sub>S (0-200 ppm) concentrations. The composition of the different gas-species varied according to the geological context. The <strong>CO<sub>2</sub></strong> concentrations varied between 0.96 and 98.08 %. The highest values were measured in the the Quaternary volcanic area of Ciomad, and also in the neighbouring thrusted and folded area of the Carpathian Flysch which suggests a tectonic control over the appearance of the gas emissions.</p><p>The <strong>CH<sub>4</sub></strong> concentrations ranged between 0.21 and 6.76% and were higher at hydrocarbon-prone areas, such as the sedimentary deposits of the Transylvanian Basin and Carpathian Flysch. In these cases the CO<sub>2</sub> concentrations were low (up to 4.6%).</p><p>The <strong>H<sub>2</sub>S</strong> concentrations varied between 0.21 and 200 ppm, according to our knowledge, these are the first H<sub>2</sub>S in-situ measurements in the gas emissions of the study area. The concentrations of H<sub>2</sub>S were higher at the volcanic area of Ciomad, reaching values above the detection limit (~200 ppm) which are related to volcanic degassing.</p><p>In conclusion, based on the investigated sites, there is a spatial correlation between the appearance of mineral water springs, gas emissions on surface and the neighbouring tectonic structures. The Multi-Gas proved to be a useful tool in the in-situ investigation of gas emissions of the Eastern Carpathians, being efficient especially for the measurement of the H<sub>2</sub>S concentrations that are very sensitive for oxidation processes.</p><p><strong>Bibliography:</strong></p><p>1.Kis B.M., Caracusi, A., Palcsu, L., Baciu, C., Ionescu, A., Futó, I., Sciarra, A., Harangi, Sz., Noble Gas and Carbon Isotope Systematics at the Seemingly Inactive Ciomadul Volcano (Eastern‐Central Europe, Romania): Evidence for Volcanic Degassing, Geochemistry, Geophysics, Geosystems, vol.20, issue 6, 2019, 3019-3043.</p>