SUMMARY
Western Slovenia is part of an actively deforming region accommodating anticlockwise rotation of Adria and its continuous collision with Eurasia. The geometry of the active faulting system in ...this plate boundary is not well defined. In this study, detailed analysis of earthquake activity was performed with relocation of earthquakes in the period between 2006 and 2017. With inspection of the waveform data, slight temporal clustering of activity was observed. To increase the detection rate of microearthquakes we used a matched filter detection algorithm method. Templates of earthquakes were created and a database of continuous waveform data within the period 2006–2017 was investigated. As a result, high temporal correlation allowed us to identify swarms and earthquake sequences that affected the active fault system in the study region.
Relocated seismicity allowed us to constrain the geometry of 5 nearly parallel faults, namely: Ravne, Idrija, Predjama, Selce and Raša faults. All these faults do have an expression in the geomorphology and reach a seismogenic depth of up to 20 km. Vertical and along strike extents of these active faults can favour earthquakes of moment magnitude equal to 7 or larger. The most recent large earthquake that occurred in this region is the 1511 earthquake with a magnitude 6.8.
The leading fault in the system being the Idrija right-lateral strike-slip fault, experiences earthquake activity from 5 to 20 km on its northern segment, while on its southern segment no earthquake activity is detected over the decade of observations. We show that the interseismic loading on the southern segment of Idrija fault is likely unclamping the locked adjacent faults promoting the observed bursts of seismicity. Moreover, in 2009 the Predjama fault accommodated a sudden increase of the surface deformation at the extensometer accompanied by a simultaneous swarm activity at its seismogenic depth. This behaviour might correspond to velocity strengthening and weakening processes taking place at both the surface and depth terminations of a locked vertical fault. These processes can be driven by a slow-slip event on the deeper part of Idrija fault that would generate a temporary acceleration of the interseismic loading rate along with a change within the fluid circulation.
Black deposits covering speleothems, cave walls and floors in Postojna Cave and Predjama Cave (SW Slovenia), and charcoal found in soil outside the Postojna Cave, were studied in order to establish ...their origin and age. SEM/EDS analysis of these deposits from both caves indicated that they are charred plant remains, very similar to oxidised charcoal in soil. Stable carbon isotope δ13C values of −29.41‰ (Črna Jama, P1), −26.9‰ (Predjama), and −25.1‰ (charcoal in soil) confirm their origin from biomass burning. Radiocarbon dating from Postojna Cave (Črna Jama (P1) 8394±35calyrB.P. and Pisani Rov 8235±25calyrB.P.) suggests that the oldest analysed black deposits formed in the Early Holocene (Mesolithic). The age is consistent with soil charcoal found at 1m depth in the surrounding area. Black deposits from Predjama were dated to 4095±25calyrB.P. (Eneolithic) and were caused by burning fires at the cave entrance, as supported by archaeological remains. Prehistoric (2375±20calyrB.P.) charcoal from the upper part of the soil profile (0.5 to 0.6m) and historic (1240±29calyrB.P. or 745calyrCE) black deposits from Postojna Cave (Črna Jama, P2) are related to forest fires, which are most likely human-induced. We interpret the oldest dated black deposits in Postojna Cave as traces of Early Holocene natural forest fires, since fire activity inside Črna Jama and Pisani Rov is not supported by archaeological remains. Favourable cave entrance morphology and microclimate allowed smoke to enter the cave during the winter period and deposit on speleothems. But an anthropogenic cause of forest fires cannot be excluded, since there are well-documented Mesolithic archaeological cave sites located close to the area. The study shows that black deposits on speleothems in caves are an important palaeoenvironmental record and proxy for Holocene climate.
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•Black deposits on speleothems and charcoal in soils in karst area were studied.•SEM/EDS, 14C dating, C stable isotope analysis, organic matter analyses were applied.•Black deposits and charcoal in soil proved forest fires event dating 8200calyrB.P.•Black deposits on cave speleothems are important proxy for Holocene climate.
Historical air temperatures at three karst caves in Slovenia have been compared to current data time series. In Postojnska Jama (PJ), the most visited show cave in Slovenia, the significant ...temperature difference between historical and modern measurements at the Pulpito site relates to the months April to November. Mean monthly temperatures measured at the Sepolcro site (PJ) in the modern period (2016–2019) are year round significantly higher than in the historical period (1935–1937). The temperature increase over the last 85 years in PJ is attributed to outside temperature rise and additional heat input from visitors, especially for Sepolcro site. A comparison of current (2017–2019) and historical (1956–1957) temperature data in touristically poorly visited Predjama Cave shows lower increase as in PJ and is completely related to outside cave conditions. In the case of Škocjanske Jame (Tiha Jama), air temperature has not significantly increased since the historical 1928 measurements because the monitoring site looks to be morphologically isolated from significant impacts of outside climate and visitors.
In August 2009 a continuous cave-air temperature monitoring programme was initiated to help improve the understanding of natural microclimate conditions in Predjama Cave one of 10,700 karst caves in ...Slovenia. Whereas Predjama Castle, which is build partly in the shelter of one of the cave's entrances, is among the most popular and spectacular tourist destinations in Slovenia, Predjama Cave currently attracts fewer visitors. Studies of the cave microclimate are being conducted to help determine the potential impact of increased tourist visits on the natural cave environment. Recently recorded visitor numbers create no notable impact on the natural cave microclimate. However, increased tourist traffic and additional heat generated by proposed electrical installations could elevate air temperature in the cave. Provision of sustainable precautions to minimize such anthropogenic effects on the cave microclimate and cave fauna must be considered in any future planning for the development of Predjama Cave as a show cave.
•Predjama Cave in Slovenia has big potentials for increased tourism in the future.•Continuous cave-air temperature monitoring initiated to understand microclimate.•Sustainable environmental precautions in future planning must be considered.
High floods of September 2010 partly ruined historic inscription made by charcoal »Slovenski gadje 1882« in Predjama cave system. Regarding studied historic records the September 2010 floods were the ...highest in Predjama at least since 1882. If we thrust the well-documented floods in 1826 they can even be higher than ones in 2010. In 2010 the water reached 489.60 m above the sea level at entrance parts of the cave and about 485 m at Vetrovna Luknja causing that the old inscription from 1882 was under water and partly destroyed. Another old inscription »Nagel 1748«, probably done by more resistant pencil, did not suffer from the 2010 floods. Contrary, it was twice partly destroyed by carless visitors, first in 1991 and secondly in the period 1991 – 2005.
Monitoring of air temperature takes place at five locations in two cave systems. At monitoring location Velika gora (Postojna 1), mean air temperature for the time period 2009–2010 was 11.10 °C. Of ...three monitoring locations Velika gora is situated at the highest absolute height. Mean air temperature in the same period was 10.66 °C in the central part of the Lepe jame cave (Postojna 3) and 10.30 °C in the side passage (Postojna 2). Temperature difference between outside and cave temperature is the highest at Postojna 2 monitoring location, due to the inflow of the air currents from the unknown parts, especially in winter time. Manual temperature measurements (2004–2010) exhibit slight increase of air temperature at Postojna 1 and Postojna 2 monitoring sites. In the Predjama cave system, the air temperature in Velika dvorana is much more stable than in Konjski hlev passage, which is more subject to external influences.
Imenski rov (Rov starih podpisov), the Old Cave (Stara jama), was the only part of Postojnska jama known for several centuries until 1818 when Luka Čeč discovered the access to the inner parts of the ...cave. Here we documented ca. 400 inscriptions. About 100 more were also recorded in the historic part of Predjama Cave. From these signatures we correlated 19 with independently historically known persons, less than 5% of the total. The correlation is firm for 15 names, but only tentative for Bellegarde, Kotze, Mihanović and Karl von Zur. The oldest one is that of Johann Melchior Ott(o) of 1642, a painter in the service of Johann Anton zu Eggenberg (1610–1649) the owner of the Castle of Adelsberg at the time, whose coat of arms Ott drew as well. The next oldest is the name Josef Anton Nagel 1748 who also left Latin inscriptions in Predjama cave and in Sloup Cavern, Moravia. All other inscriptions of historic persons are younger than 1800 including those of Franz Graf von Hohenwart, Joseph Petsch Ritter von Löwengreif and Alois Schaffenrath (each with several inscriptions). Noteworthy are also the signatures of Josef Franz Eggenhöfner (1801 or 1809, and 1820; developer of Grotta di Padriciano), Johann Natterer (biologist, 1815, who stayed 19 years in Brazil and laid the basis of the zoological department of the Natural History Museum in Vienna), Karl Beyrich (1819, botanist who died during an expedition in Arkansas, 1834), Giuseppe de Volpi (1820, from Trieste who published first evidence of the cave bear presence in Postojnska jama), Johann Fercher, mine supervisor, and his team of miners from Idrija who signed during their survey of the cave in 1833, Johann Ritter von Hauer (1836 in Pisani rov, Vienna, Imperial Councelor of War and Palaeontologist), Ivan Andrej Perko (the later director of the cave) and several cave guides. Members of the nobility or state employees include Bellegard, Adrienne Brandis Desenffans and her brother Karl Graf Desenffans, Carl von Kotze, and Mihanović.
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Provider: - Institution: - Data provided by Europeana Collections- All metadata published by Europeana are available free of restriction under the Creative Commons CC0 1.0 Universal Public Domain ...Dedication. However, Europeana requests that you actively acknowledge and give attribution to all metadata sources including Europeana
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