Geophysical investigations in the Radovna River Spring area (Julian Alps, NW Slovenia)

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 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 fluctuating and 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.

Application of Combined Geophysical Methods for the Examination of a Water Dam Subsoil

The paper presents the results of geophysical measurements that were carried out in the vicinity of the water dam/water reservoir supplying the city of Bielsko-Biala with drinking water. The measurements were performed in order to non-invasively detect faults, fractured zones and areas filled with breccia, which may be, at the same time, a preferential path of groundwater flow. The aforementioned factors influence the stability of the dam. The general identification of the examined media was realized by the electrical resistivity tomography method. The ERT surveys were supplemented by capacitively-coupled resistivity. The electrical methods allowed them to recognize geological settings, indicate possible fault locations, and point out the fault plane as a path of water flow. The ground penetrating radar method detected fractured and filled water areas and underground water paths in the dam’s forefield as a result of the method’s very high resolution. The high resolution seismic reflection method provided a clear and high resolution image of the relatively deep geological structure and verified a location and the run of the faults. In general, the complex geophysical-geological interpretation enabled classification of the unconsolidated/fractured zones associated with faults as a place where the erosion process is the most intense and can bring danger on the dam. Finally, it was confirmed that the area should be the subject of geophysical monitoring.

The nature of regional magnetic anomalies in the northeast of the Barents-Kara continental margin based on the results of seismic data interpretation

Based on the interpretation of seismic sections via seismic reflection method, the lines of which intersect the positive magnetic anomalies in the St. Anna Trough and on the North Kara Shelf, the authors have substantiated the position of the Early Cretaceous dike belt in the north of the Barents-Kara platform for the first time. They traced the belt from the arch-block elevation of arch. Franz Josef Land, which belongs to the Svalbard platе through the Saint Anna Trough and further into the Kara platе to arch. Severnaya Zemlya. The distinguished dyke belt has discordant relationships with the structural-tectonic plan of the region under consideration. The authors illustrate the manifestations of dyke magmatism in the marked tectonic elements in seismic sections, and conclude that the dyke belt relates to the formation of the structural system of the Arctic basin.

Shallow seismic reflection survey for imaging deep-seated coal layer - Case study from Muara Enim coal

Indonesia has a great potential for deep-seated coal resources. To assist and support the deep-seated coal exploration, a shallow seismic reflection method is applicable for this purpose. This study has conducted a shallow seismic reflection method in Musi Banyuasin Regency, South Sumatera Province. The Muara Enim coal target varies from 100 to 500 meters from the surface. The thickness of the coal layer varies from 2 to 10.65 meters. This study uses 48 channels with 14 Hz single geophone and MiniSosie as the energy source. The receiver and source interval is 15 meters. This study uses a fixed receiver and moving source configuration. From the interpreted seismic section, this study identified a deep-seated coal layer target. These layers are Mangus, Burung, Benuang, Kebon and Benakat layers. A simple interpretation is analyzed by combining the seismic amplitude characteristics and the thickness of the coal layer from the borehole data. From the interpreted seismic section, deep-seated coal layer targets have strong amplitude characteristics and are continuous from southwest to the northeast with a down-dip of around 20-30°. This study helps to inform the operator companies who develop the utilization of deep-seated coal (coalbed methane, underground coal gasification and underground coal mining) about the effective and proper geophysical method for imaging deep-seated coal layer.

Application of combined electrical resistivity tomography and seismic reflection method to explore hidden active faults in Pingwu, Sichuan, China

Pingwu County, which is located at the northern end of the Longmenshan fault structural belt, has an active regional geological structure. For a long time, the Longmenshan fault tectonic belt has become intensely active with frequent earthquakes. According to the existing geological data, the Pingwu–Qingchuan fault passes through the urban area of Pingwu. However, because of the great changes in the original landform of Pingwu caused by the construction activities in this urban area, a precise judgment of the location of the Pingwu–Qingchuan fault according to the new landform characteristics is difficult. Here, the seismic reflection method, electrical resistivity tomography (ERT), and drilling method were used to determine the accurate location of the buried active faults in Pingwu County. The seismic reflection method and ERT are used to determine the location of faults, the thickness of overlying strata of the fault, and the basic characteristics of faults. The drilling data can be used to divide the bedrock lithology and confirm the geophysical results. The geological model of the faults can be constructed by 3D inversion of ERT, and the structural characteristics of the faults can be viewed intuitively. The results of this study can provide a basis for earthquake prevention and construction work in Pingwu. The finding also shows that seismic reflection method and ERT can effectively explore buried active faults in urban areas, where many sources of interferences may exist.

Application of Specific Energy in Evaluation of Geological Conditions Ahead of Tunnel Face

In underground construction, especially tunnel building, a detailed knowledge of the geological conditions ahead of the tunnel face is essential for both safety and efficiency of work. Many tunnel collapses have been reported to occur because of a lack of accurate evaluation of the geological conditions. While conventional horizontal boring conducted from a tunnel face provides good accuracy, it is infrequently conducted due to its high cost and time-consuming nature. In addition, the tunnel seismic reflection method has limited practicality owing to the complexity of data processing. This paper presents a new approach based on the specific energy of the mechanical drilling rig to evaluate the geological conditions ahead of the tunnel face. In order to assess the geological conditions, rock mass quality index, buried depth of the tunnel and tunnel deformation investigation were undertaken, and the obtained data were compared to the specific energy. Results from the comparison reveal the evaluation criterion that if the distribution of specific energy in some areas deviates from the distribution of buried depth, it is considered that abnormal geological conditions exist in this area. This work can greatly contribute to the accurate and effective evaluation of the geological conditions ahead of the tunnel face.