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Query: "author" (Andrej Gosar) .

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1.
Seismogenic depth and seismic coupling estimation in the transition zone between Alps, Dinarides and Pannonian Basin for the new Slovenian seismic hazard model
Polona Zupančič, Barbara Šket Motnikar, Michele M. C. Carafa, Petra Jamšek Rupnik, Mladen Živčić, Vanja Kastelic, Gregor Rajh, Martina Čarman, Jure Atanackov, Andrej Gosar, 2024, original scientific article

Abstract: 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 Alps, Dinarides and Pannonian Basin, characterized by a complex deformation pattern, highly variable crustal thickness, and moderate seismic hazard, supporting the development of the 2021 seismic hazard model of Slovenia. The hazard model was based on three seismic source models: area source model, fault source model and smoothed seismicity (point) source model. We estimated the lower seismogenic depth using seismological and geological data and compared them. The seismological estimate was based on two regional earthquake catalogues prepared for this study. In the area source model, estimates of lower seismogenic depth from seismological data are deeper or equal to the ones derived from geological data, except in one case. In the fault source model, we analysed each fault individually and chose seismological lower depth estimates in 12 among 89 faults as more representative. The seismogenic thickness for each individual fault source was determined for seismic coupling determination. The seismic coupling was assessed by two approaches, i.e. we chose the most trusted value from the literature, and the value determined for each fault individually by using the approach based on the updated regional fault and earthquake data sets. The final estimate of seismic coupling ranges from 0.77 to 0.38. We compared the tectonic moment rate based on long-term slip rate using different values of seismic coupling with the seismic moment rate obtained from the earthquake catalogue. The analysis is done for the whole area, as well as for the individual area zones. The analysis of N–S components of estimated slip for the largest faults in the area of west Slovenia shows that the regional geological and geodetic shortening rates are comparable. The total activity rate of three global seismic source models is compared, which gives up to a 10 % difference. Our results contribute to a better understanding of the seismic activity in the region. The presented approach for seismic coupling estimation can be applied in cases where the total slip rate is given instead of its seismic part and can be used at regional or national level. The approach is also suitable for the cross-border harmonization of the European seismic hazard modelling data.
Keywords: seismic hazard, modeling, Slovenia
Published in DiRROS: 18.03.2024; Views: 68; Downloads: 41
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2.
Geophysical investigations in the Radovna River Spring area (Julian Alps, NW Slovenia)
Anja Torkar, Marjana Zajc, Jure Atanackov, Andrej Gosar, Mihael Brenčič, 2021, original scientific article

Abstract: 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 aquif er two geophysical methods were used in our study; ground penetrating radar (GPR) and seismic reflection method. The low-frequency GPR method has shown to be useful for determining the depth of the groundwater and the predominant groundwater recharge. Also, the high-resolution seismic method provided an insight about the morphology of the pre-Quaternary basement with the deepest point at 141 meters below surface. Measurements of hydrogeological parameters such as groundwater level and river discharge measurements were carried out in the study area. Both data analyses showed that groundwater level and river discharge are highly fluctuatingand rapidly changing, indicating a well-permeable aquifer, implying that such an aquifer is extremely sensitive and vulnerable to extreme climate events. Both the geophysical methods and the hydrogeological information have provided important information about the morphology of the valley and the alluvial aquifer, as well as increasing the knowledge about the Radovna springs system, which will contribute very important information for future hydrogeological studies.
Keywords: Ground penetrating radar, Seismic reflection method, Radovna spring, hydrogeology, aquifer geometry, glacial valley, groundwater table
Published in DiRROS: 09.03.2022; Views: 669; Downloads: 306
.pdf Full text (6,27 MB)

3.
GPR survey to reveal a possible tectonic tilt of the Brežice Sava River Terrace in the Krško Basin
Marjana Zajc, Marijan Poljak, Andrej Gosar, 2021, original scientific article

Abstract: 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 the lower boundary of the terrace, which consists of loose to poorly cemented Quaternary gravel, while its Tertiary basement consists of poorly cemented carbonaceous silt (marl). The premise of the study was the assumption that this lithological boundary could be detected by the GPR method. In addition to the upper surface of the BSRT being tilted to the north by 0.18°, GPR profiles also showed a 0.04° difference in the tilt between the upper surface of the terrace and its lower boundary with the basement, which we assigned to the sin-sedimentary tilt. Upon this information, a cumulative tectonically induced dip of the BSRT lower boundary was defined at 0.22°.
Keywords: Brežice Sava River terrace, Krško basin, ground penetrating radar, tectonic tilt, seismic reflection profiling
Published in DiRROS: 06.01.2021; Views: 1359; Downloads: 628
.pdf Full text (4,88 MB)

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