Andrej Gosar

University of Ljubljana · Faculty of Natural Sciences and Engineering

The area of the NW Dinarides lies in the northeastern corner of the Adriatic microplate – a promontory of the African plate – which plays a major role in the collision processes occurring in the peri-Adriatic region. Taking advantage of the greatly increased amount of data due to the modernization of the Slovenian seismological network, improved cr...

Seismogenic depth and seismic coupling are important inputs into seismic hazard estimates. Although the importance of seismic coupling is often overlooked, it significantly impacts seismic hazard results. We present an estimation of upper and lower seismogenic depth and expected hypocentral depth and seismic coupling in the transition zone between...

The seismogenic depth and seismic coupling are important inputs into seismic hazard estimates. Although the importance of seismic coupling is often overlooked, it significantly impacts seismic hazard results. We present an estimation of upper and lower seismogenic depth and hypocentral depth and seismic coupling in the transition zone between the A...

Slovenia is an earthquake-prone country with a moderate seismic hazard, characterized by relatively long recurrence intervals for strong earthquakes. With newly compiled data and revised info on active faults of the region, we are now able to supplement and enhance the probabilistic seismic hazard assessment, which was previously based mainly on th...

The studied area of the northwestern (NW) Dinarides is located in the northeastern (NE) corner of the Adriatic microplate and is bordered by the Adriatic foreland, the Southern Alps, and the Pannonian basin. Its complex crustal structure is the result of interactions among different tectonic units, the most important of which are the Eurasian plate...

The Radovna River Valley is located in the north-western part of Slovenia in the Julian Alps, where there is an extensive intergranular aquifer whose depth to pre-Quaternary bedrock is unknown. Therefore, to obtain information about the depth of the valley and the geometry of the aquifer two geophysical methods were used in our study; ground penetr...

The investigated area of the NW Dinarides is located at the NE corner of the Adriatic microplate and is bordered by the Adriatic foreland, the Southern Alps, and the Pannonian basin. Its complex crustal structure is the result of interactions among different tectonic units, mainly the Eurasian plate and the Adriatic microplate. Despite numerous sei...

The AlpArray Gravity Research Group (AAGRG), as part of the European AlpArray program, focuses on the compilation of a homogeneous surface-based gravity data set across the Alpine area. In 2017 10 European countries in the Alpine realm agreed to contribute with gravity data for a new compilation of the Alpine gravity field in an area spanning from...

The AlpArray Gravity Research Group (AAGRG), as part of the European AlpArray program, focuses on the compilation of a homogeneous surface-based gravity dataset across the Alpine area. From this data set, Bouguer- and Free Air anomalies are calculated and presented here. In 2016/17 ten European countries in the Alpine realm have agreed to contribut...

It has been supposed that the Brežice Sava River Terrace (BSRT) is tectonically disturbed near the town of Brežice and tilted to the north. To confirm this tectonically induced tilt in a quantitative sense, low-frequency Ground Penetration Radar (GPR) was applied. A total of eight GPR profiles were recorded across the BSRT providing information of...

A recent slip-rate of an active fault is a very important seismotectonic parameter, but not easy to determine. Idrija fault, 120 km long, is a prominent geomorphologic feature with large seismogenic potential, still needed to be researched. Measurements of tectonic micro-displacements can provide insight into its recent activity. The Učja valley ex...

Knowledge about the crustal thickness is one of the key elements in the reconstruction of the regional tectonic history. The Dinaric mountain belt is one of the most enigmatic segments of the Alpine‐Mediterranean collision zone, characterized by large variations in crustal thickness and not studied sufficiently. We present a new Moho depth map for...

Karst as an extremely complex and heterogeneous system, that presents a great challenge for the ground penetrating radar (GPR). However, properly planed GPR surveys can provide additional information about the shallow subsurface, where most karst processes take place. Due to the specific nature of the karst terrain, the introductory part presents s...

Overview of extensive seismological studies of Krn Mountains earthquakes performed in two decades is given. Detailed macroseismic studies by using a new European Macroseismic Scale EMS-98 showed large variations in damage to buildings due to the influence of very heterogeneous sediments and partly also due to the differences in source radiation pat...

A review of geological and seismotectonic investigations conducted in the two decades after the 12 April 1998 earthquake in Krn Mountains, according to its magnitude the strongest earthquake in Slovenia in the 20th century, is given. Many of these studies have wider scientific meaning than expected from the size of the earthquake. This was the firs...

The 1998 Krn Mountains Mw 5.6 earthquake had widespread effects on the natural environment, among which rockfalls prevail. All rockfalls were evaluated to estimate the total affected area. The 180 km2 area (r=7.6 km) was established and compared with two worldwide datasets. The affected area is considerably below the upper bound limit established f...

After conducting a successful GPR pilot study in a tectonically complex area of the Karst Thrust Edge, a follow-up study was carried out. In the pilot study, the geometry and spatial extent of the Socerb thrust-fault, which separates limestone above from flysch below, were investigated using a 50 MHz antenna in the Črnotiče quarry. After one part o...

Ground penetrating radar (GPR) named “Roteg” was used to detect known and unknown passages of Divaška Jama and Trhlovca caves in SW Slovenia. “Roteg’s” main characteristics are an extraordinary high power output (20 MW) and high voltage on antennas (up to 20 kV), which allows penetration more than ten times deeper than common GPRs. During the measu...

Earthquake activity rate estimation for seismic hazard analysis.

Ground penetrating radar (GPR), a non-destructive geophysical method, was used to detect cave sediments, now exposed on the karst surface (in so-called “unroofed caves”) due to a general lowering of the surface (dissolution of carbonate rocks). It turned out that cave sediments are expressed as areas with strong signal attenuation on GPR radargrams...

Ground penetrating radar (GPR) using a special unshielded 50 MHz Rough Terrain Antenna (RTA) in combination with a shielded 250 MHz antenna was used to study the capability of this geophysical method for detecting cave sediments. Allochthonous cave sediments found in the study area of Lanski vrh (W Slovenia) are now exposed on the karst surface in...

Verjetnostno ocenjevanje potresne nevarnosti upošteva učinke potresov različnih magnitud z vseh znanih potresnih izvorov na nekem območju. Izhodišče za opredelitev in parametrizacijo prelomnih potresnih izvorov predstavljajo aktivni prelomi, ki so bili v zadnjih letih na območju Slovenije predmet obsežnih raziskav. Na izračun potresne nevarnosti v...

On Kranjsko polje in central Slovenia, carbonate conglomerates have been dated to several Pleistocene glacial phases by relative dating based on the morphostratigrafic mapping and borehole data, and by paleomagnetic and 10Be analyses. To define how the age of conglomerates determines the geomorphological characteristics of karst surface features, m...

The ground penetrating radar (GPR) method was applied for the differentiation of rock layers within a heterogeneous turbidite, a multi-layered sedimentary formation that is formed by the resedimentation of vast amounts of material from underwater landslides and slope failures. The aim of the study was to determine the presence of discontinuities an...

The bare karst surface in the southeastern part of Krk Island (Croatia) is characterized by different surface karst features, such as valley-like shallow linear depressions and partially or fully sediment-filled depressions of various shapes and sizes. They were noticed due to locally increased thickness of sediment and enhanced vegetation but had...

Outcome of COST Action TU1208: A glossary of Ground Penetrating Radar terms in 15 languages spoken in COST Countries

In this paper we present the results of monitoring of temperatures in the air, soil and a borehole V-8/86 at Malence near Kostanjevica in the southeast Slovenia. The results include the temperatures measured in the period from year 2011 to 2015. Highlights of the paper are mainly on the inflence of heavy rainfall on temperatures in the upper parts...

The town of Idrija is located in an area with an increased seismic hazard in W Slovenia and is partly built on alluvial sediments or artificial mining and smelting deposits which can amplify seismic ground motion. There is a need to prepare a comprehensive seismic microzonation in the near future to support seismic hazard and risk assessment. To st...

The new railway route Divača - Koper is planned to cut through the Karstic thrust edge, a prominent geomorphologic step within the active Adria - Dinarides thrust zone. This represents a major obstacle for the railway construction, therefore it is crucial to understand the structural properties and the geometry of the thrust-fault planes within the...

The 12 April 1998 Mw5.6 Krn Mountains earthquake with a maximum intensity of VII-VIII on the EMS-98 scale caused extensive environmental effects in the Julian Alps. The application of intensity scales based mainly on damage to buildings was limited in the epicentral area, because it is a high mountain area and thus very sparsely populated. On the o...

Since 2002 the Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS) in Udine (Italy), the Agencija Republike Slovenije za Okolje (ARSO) in Ljubljana (Slovenia) and the Zentralanstalt für Meteorologie und Geodynamik (ZAMG) in Vienna (Austria), are collecting, analyzing, archiving and exchanging seismic data in real time, initially in...

The Idrija town is located in area with increased seismic hazard in W Slovenia and is partly built on alluvial sediments or artificial mining and smelting deposits which can amplify seismic ground motion. There is a need to prepare a comprehensive seismic microzonation in the near future to support seismic hazard and risk assessment. To study the a...

Potresno nevarnost ocenjujemo z determinističnim (DSHA) ali verjetnostnim (PSHA) pristopom. Danes PSHA pripisuje velik pomen seizmotektonskim podatkom, ki jih podajamo predvsem v obliki aktivnih prelomov in seizmotektonskih območij. Aktivni prelomi v Sloveniji so bili v zadnjih letih predmet obsežnih raziskav. Rezultati so spodbudili natančnejšo an...

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 morpho-tectonic an...

In areas experiencing low deformation rates, landscapes provide limited evidence of ongoing tectonic activity, being either masked or altered by exogenic processes. Accordingly, the identification of fault activity and near surface deformation is commonly accomplished by multidisciplinary research combining geological, geophysical and geomorphic me...

The S-19 Cave was with its explored depth of 177 m one of the most important caves of the Mt. Kanin massif, but after its discovery in 1974, a huge snow avalanche protection dyke was constructed across the cave entrance. To excavate the buried cave, the accurate location of the cave had to be determined first. Since the entrance coordinates were in...

With the aim of monitoring the seismic activity in the eastern sector of the Alps, since 2001 OGS (Istituto Nazionale di Oceanografia e di Geofisica Sperimentale, Bragato et al., 2011) in Udine (Italy), the Agencija Republike Slovenije za Okolje (ARSO) in Ljubljana (Slovenia), the Zentralanstalt für Meteorologie und Geodynamik (ZAMG) in Vienna (Aus...

Ljubljana is one of three regions with the highest seismic hazard in Slovenia. In addition soft sediments in the Ljubljana basin have a strong influence on seismic ground motion. We used macroseismic data to investigate the influence of local geological structure on earthquake intensities in greater Ljubljana area. We determined intensities for ele...

Since 2002, OGS (Istituto Nazionale di Oceanografia e di Geofisica Sperimentale) in Italy, the Agencija Republike Slovenije za Okolje (ARSO) in Slovenia, and the Zentralanstalt für Meteorologie und Geodynamik (ZAMG) in Austria are exchanging seismic data in real time. The data exchange is very effective for seismic events at the borders between Ita...

The region of central and eastern Europe is an area characterised by a relatively high seismic risk. Since 2001, to monitor the seismicity of this area, the OGS (Isti-tuto Nazionale di Oceanografia e di Geofisica Sperimentale) in Italy, the Agencija Republike Slovenije za Okolje (ARSO) in Slovenia, the Zentralanstalt für Meteorologie und Geo-dynami...

The Karstic thrust edge, a pronounced geomorphologic step, which is a result of the tectonostratigraphic evolution of the active Adria–Dinarides thrust zone, represents a major obstacle for the planned new railway route Divača–Koper. Thus, the geotechnical and structural properties as well as the geometry of the thrust-fault planes in this area are...

Geophysical investigations were conducted using electrical resistivity tomography (ERT) along planned dykes of the HPP Brežice water accumulation basin. The ERT profile is 7.3 km long and is located on the right riverbank of the Sava River on the Kr{ko-Brežice field (E Slovenia). A purpose of the investigations was to determine a boundary between s...

Aiming at the seismic risk mitigation in the eastern sector of the Alps, since 2002 OGS (Istituto Nazionale di Oceanografia e di Geofisica Sperimentale) in Udine (Italy), the Agencija Republike Slovenije za Okolje (ARSO) in Ljubljana (Slovenia) and the Zentralanstalt für Meteorologie und Geodynamik (ZAMG) in Vienna (Austria) are collecting, analyzi...

Since 2002 OGS (Istituto Nazionale di Oceanografia e di Geofisica Sperimentale) in Udine (Italy), the Agencija Republike Slovenije za Okolje (ARSO) in Ljubljana (Slovenia) and the Zentralanstalt für Meteorologie und Geodynamik (ZAMG) in Vienna (Austria), are collecting, analyzing, archiving and exchanging seismic data in real time. The data exchang...

The region of the Central and Eastern Europe is an area characterised by a relatively high seismicity. The active seismogenic structures and the related potentially destructive events are located in the proximity of the political boundaries between several countries existing in the area. An example is the seismic region between the NE Italy (FVG, T...

Since 2002 the OGS (Istituto Nazionale di Oceanografia e di Geofisica Sperimentale) in Udine (Italy), the Agencija Republike Slovenije za Okolje (ARSO) in Ljubljana (Slovenia) and the Zentralanstalt für Meteorologie und Geodynamik (ZAMG) in Vienna (Austria) are collecting, analyzing, archiving and exchanging seismic data in real time. The data exch...

We evaluated the use of ground penetrating radar (GPR) in detecting karst cavities and discontinuities that could form potential landslide surfaces in flyschoid rocks of the Rodež open pit mine in Anhovo (W Slovenia). We recorded 21 GPR profiles in three consecutive benches with the unshielded 50 MHz rough terrain antenna (RTA) system, and correlat...

Two moderate magnitude (Mw = 5.6 and 5.2) earthquakes in Krn Mountains occurred in 1998 and 2004 which had maximum intensity VII-VIII and VI-VII EMS-98, respectively. Comparison of both macroseismic fields showed unexpected differences in the epicentral area which cannot be explained by site effects. Considerably, different distribution of the high...

During the exploitation of flyschoid rocks in quarries, the presence of karst features such as caves and phreatic channels in carbonate units can be extremely hazardous. Several case studies to date have shown that the Ground Penetrating Radar (GPR) is a suitable method for detecting such features. We evaluated its use in detecting karst caves and...

The convergent boundary zone surrounding the Adriatic Sea represents the major component in the larger tectonic framework of the Mediterranean area. Dinarides, as a part of this convergence zone, are usually seen as the region where the interaction between Adriatic microplate and the Eurasian mainland was initiated. During the structural evolution...

Located in central Europe between the southern Alps and the Dinarides, the≈ 100km long Idrija fault, striking N310 and dipping ≈ 80°NE is often considered as the potential source of the 1511 earthquake (estimated magnitude: 6.9). However, although continental earthquakes of similar size are almost invariably associated with surface faulting, no sur...

Breginjski kot is among the most endangered seismic zones in Slovenia with the seismic hazard assessed to intensity IX MSK and the design ground acceleration of 0.250 g, both for 500-year return period. The most destructive was the 1976 Friuli Mw = 6.4 earthquake which had maximum intensity VIII-IX. Since the previous microzonation of the area was...

Two seismic sources were tested on different surfaces during acquisition of a 5.5-km long high resolution seismic reflection (HRS) profile on the Ljubljana Moor in central Slovenia. Maximum target depth range of the survey was 200 - 300 m. Nine different combinations of source-surface conditions were analysed. Seismic sources included a seismic sho...

During heavy rainfalls between September 17 and 19, 2010 large part of Slovenia has suffered extensive floods that last for nearly two weeks. For the river Iška record discharge of 59.3 m3/s was measured on September 19 on the gauging station in Iška vas located at the southern rim of Ljubljansko barje. In the first hour of September 21, 2010 two w...

Site effects studies using microtremor free-field measurements were performed recently in five Slovenian towns characterized by increased seismic hazard to determine resonance frequency of soft sediments. In this study, microtremor investigations were extended to the measurements inside buildings to determine their fundamental frequencies and to as...

The 12 April 1998 Mw = 5.6 Krn Mountains earthquake with a maximum intensity of VII-VIII on the EMS-98 scale caused extensive environmental effects in the Julian Alps. The application of intensity scales based mainly on damage to buildings was limited in the epicentral area, because it is a high mountain area and thus very sparsely populated. On th...

High frequency ground penetrating radar (GPR) is usually applied for cavities detection in a shallow subsurface of karst areas to prevent geotechnical hazards. For specific projects, such as tunnel construction, it is important to detect also larger voids at medium depth range. However, dimensions of classical rigid low frequency antennas seriously...

Seismicity of the Ljubljana Basin, the most densely populated area of Slovenia, is evaluated as "moderate" with a seismic hazard characterized by design ground acceleration of 0.25 g and expected intensity VIII EMS-98 for a return period of 475 years. So far the seismic hazard has been evaluated solely on the basis of historic seismicity, the large...

The town of Litija was hit by four damaging earthquakes in the last 120 years which reached a maximum intensity of VII-VIII MSK. The town is located in a shallow sedimentary basin filled with relatively soft Quaternary sediments in which seismic site amplification is expected. On the other hand no borehole or geophysical data are available to suppo...

At the end of 2010 seven TM 71 extensometers, installed at or near the active faults in Slovenia, were in operation. Three of them are on the surface and four inside karst caves. The highest rates with stable sense of movements were observed on the Idrija fault. Average horizontal displacement rate was 0.24 mm/year. Short term rates were even great...

Evropska seizmološka komisija (ESC) organizira generalno skupščino vsaki dve leti. Leta 2010 je bila generalna skupščina od 5. do 10. septembra v Montpellieru (Francija). Lokalna organizatorja sta bila Evropsko-sredozemski seizmološki center (EMSC) in Univerza v Montpellieru. Od 13. do 17. septembra je bila v prostorih oddelka Geoznanosti na Univer...

The town of Kobarid is located in one of three areas with the highest seismic hazard in Slovenia. It was hit by several 1976–1977 Friuli sequence earthquakes and recently by the 1998 and 2004 Krn Mountains earthquakes which caused damage of intensity up to VII EMS-98 scale. The town is located in a small basin filled with heterogeneous glaciofluvia...

Ljubljana, the capital of Slovenia, is located in the central region of the country in a shallow sedimentary basin filled with Quaternary deposits. It is one of the most seismically active regions in Slovenia, with some important historical earthquakes that have caused damage and economic losses. The soft sediments are some of the most important fa...

The European plate has a 4.5 Gy long and complex tectonic history. This is reflected in the present day large scale structures. The new digital Moho depth map is compiled from more than 250 data sets of individual seismic profiles, 3D models obtained by body and surface waves, receiver function results, and maps of seismic and/or gravity data compi...

The tectonic setting of W Slovenia is characterised by NW-SE trending dextral strike-slip fault systems and moderate seismicity. Monitoring of tectonic movements along five presumably active faults or in their vicinity using TM 71 extensometers was set up in 2004. In five years of monitoring some clear trends of displacement were established. The m...