Geological Faults Research Articles

Automatic interpretive image-focusing analysis

The focusing of a seismic image is directly linked to the accuracy of the velocity model. Therefore, a critical step in a seismic imaging workflow is to perform a focusing analysis on a seismic image to determine velocity errors. Although the offset/aperture-angle axis is frequently used for focusing analysis, the physical axes of seismic images tend to be ignored because the focusing analysis of geologic structures is highly interpretive and difficult to automate. We have developed an automatic data-driven approach using convolutional neural networks to automate image-focusing analysis. Using focused and unfocused geologic faults, our approach makes use of spatial and offset/angle focusing information to robustly estimate local focusing errors within seismic images. The application of our method to a 2D limited-aperture image from the Gulf of Mexico shows that it can correctly estimate local focusing errors within the image, while a traditional semblance-based approach fails. Additionally, the proposed approach has the added benefit of improving the interpretation of faults within the image.

LRSTV: A low-rank total variation-based seismic fault preserving denoising algorithm

Low-rank and total variation techniques have shown their ability in different denoising applications. In this paper, we explore the effectiveness of a combined low-rank and total variation-based denoising algorithm for the first time in seismic data pre-processing. This unified mathematical framework enables restoration of seismic data corrupted by severe degradation. The aforementioned algorithm is capable of suppressing noise without smearing sharp edges. In addition to this, it is also able to sharpen blurred edges in the data. When we apply the algorithm at the pre-processing stage, it highlights edges and discontinuities that often correspond to geological faults and fractures, thereby making structural interpretation much simpler than usual. We evaluate the method through synthetic and field datasets. Results indicate that the method is an effective and robust tool that outperforms other state-of-the art methods for seismic denoising.

Real-Time Visualization of Large-Scale Geological Models With Nonlinear Feature-Preserving Levels of Detail.

The rapidly growing size and complexity of 3D geological models has increased the need for level-of-detail techniques and compact encodings to facilitate interactive visualization. For large-scale hexahedral meshes, state-of-the-art approaches often employ wavelet schemes for level of detail as well as for data compression. Here, wavelet transforms serve two purposes: (1) they achieve substantial compression for data reduction; and (2) the multiresolution encoding provides levels of detail for visualization. However, in coarser detail levels, important geometric features, such as geological faults, often get too smoothed out or lost, due to linear translation-invariant filtering. The same is true for attribute features, such as discontinuities in porosity or permeability. We present a novel, integrated approach addressing both purposes above, while preserving critical data features of both model geometry and its attributes. Our first major contribution is that we completely decouple the computation of levels of detail from data compression, and perform nonlinear filtering in a high-dimensional data space jointly representing the geological model geometry with its attributes. Computing detail levels in this space enables us to jointly preserve features in both geometry and attributes. While designed in a general way, our framework specifically employs joint bilateral filters, computed efficiently on a high-dimensional permutohedral grid. For data compression, after the computation of all detail levels, each level is separately encoded with a standard wavelet transform. Our second major contribution is a compact GPU data structure for the encoded mesh and attributes that enables direct real-time GPU visualization without prior decoding.

Seismicity variations in space and time in the area of the Saamy fault, Khibiny Massif, Kola Peninsula

The paper analyzes the dynamics of seismicity in the vicinity of the Saamy fault, Khibiny Massif, Kola Peninsula. The qualitative recording of seismic events has been carried out there since 2008. The study area is characterized as rockburst-hazardous and complicated by a geological fault, is developed by open pit mining, and includes the Kukisvumchorr and Yukspor deposits. In order to identify the influencing factors and mechanisms of rock mass failure, the authors used the spatial–temporal clustering of data, and analyzed the location and possible causes of the clusters. The areas with long-term seismic activity near the fault and the areas with short-term increase in seismic activity which is often induced by triggering factors are detected. The clusters in the console part of the rock mass are identified. At the Yukspor deposit, rock mass failed and caved into the Saamy open pit. It is found that opencast mining with blasting in the fault zone is a trigger for the fault activation, which is confirmed by seismic events recorded not only at the working level but also higher. The seasonal increase in water inflows is an additional factor in the fault activation; some clusters are characterized by a higher level of seismic activity during such periods. According to the authors’ conclusion, the analysis of seismicity on the basis of spatial and temporal data clustering allows timely revealing of seismic activation causes and enables necessary preventive measures (rock mass destressing, sectional breaking, bulk blasting to reduce stress level, etc.), which in general reduce the risks of man-induced catastrophes.

Identification of near-fault multi-pulse ground motion

The near-fault pulse-like ground motion is of practical importance since it tends to cause severer damage to structures than ordinary ground motion in engineering and helps characterize the seismic source and the kinematic characteristics of the geological fault in seismology. However, previous investigations mainly focus on single-pulse ground motion. As one of the particular seismic records in the near-fault earthquake, the multi-pulse ground motion is rarely considered caused by the absence of an effective identification method. Hence, a generalized continuous wavelet transform (GCWT) method is proposed by combining convolution analysis with evaluation parameters to facilitate wider studies on multi-pulse ground motion. In identification, the proposed method requires each pulse in the multi-pulse ground motion to satisfy the same criteria and excludes the effects of attenuation component. In methodology, the proposed method overcomes the limitations of the classical CWT method that requires a wavelet basis and provides a workable and flexible framework for pulse-like ground motion identification. Based on the method, single- and multi-pulse ground motions from two typical near-fault earthquakes on the PEER NGA-West2 database were identified. The effects of the pulse model and ground motion orientation on identification are discussed. Besides, the 5% damped spectral velocity of multi-pulse ground motions potentially contain multiple peaks in the high-period range. This phenomenon implies that the risk would be underestimated for the response spectrum-based seismic hazards and risk analysis if the multi-pulse features are not, or are insufficiently taken into account.

Fracture Energy and Breakdown Work During Earthquakes

Large seismogenic faults consist of approximately meter-thick fault cores surrounded by hundreds-of-meters-thick damage zones. Earthquakes are generated by rupture propagation and slip within fault cores and dissipate the stored elastic strain energy in fracture and frictional processes in the fault zone and in radiated seismic waves. Understanding this energy partitioning is fundamental in earthquake mechanics to explain fault dynamic weakening and causative rupture processes operating over different spatial and temporal scales. The energy dissipated in the earthquake rupture propagation along a fault is called fracture energy or breakdown work. Here we review fracture energy estimates from seismological, modeling, geological, and experimental studies and show that fracture energy scales with fault slip. We conclude that although material-dependent constant fracture energies are important at the microscale for fracturing grains of the fault zone, they are negligible with respect to the macroscale processes governing rupture propagation on natural faults. ▪ Earthquake ruptures propagate on geological faults and dissipate energy in fracture and frictional processes from micro- (less than a millimeter) to macroscale (centimeters to kilometers). ▪ The energy dissipated in earthquake rupture propagation is called fracture energy ( G) or breakdown work ( Wb) and scales with coseismic slip. ▪ For earthquake ruptures in natural faults, the estimates of G and Wbare consistent with a macroscale description of causative processes. ▪ The energy budget of an earthquake remains controversial, and contributions from different disciplines are required to unravel this issue.

Update for reactive transport modeling of the Kızıldere geothermal field to reduce uncertainties in the early inspections

The development of carbon capture and storage techniques has become essential to reduce and mitigating CO2 emissions to the atmosphere. CarbFix1 and CarbFix2 projects carried out in Iceland demonstrated that the emissions of waste CO2 gas from geothermal power plants can be captured and mixed with the effluent geofluid and subsequently injected back into the geothermal reservoir. This experience gained in the CarbFix projects expanded into other geothermal fields around Europe, and one of the demonstration sites is the geothermal field in Turkey, Kızıldere. This paper focuses on the results of an updated study on early field evaluations with reactive transport simulations. In the new three-dimensional numerical model, the geological formations and fault zones were updated according to the well-logs data. Based on the tracer tests performed in the field, the anisotropic permeabilities between the wells were evaluated and imposed into the model. Geofluid chemistry, mineral components, and the volume fractions used as input in the simulations are modified depending on the performed laboratory experiments on the metamorphic schists taken from the geothermal site (i.e. X-ray diffraction (XRD), energy dispersive X-ray (EDX), scanning-electron microscope (SEM), and batch reactor tests). Different thermodynamic databases such as Lawrance Livermore National Laboratory (LLNL) and Thermoddem databases were tested using PHREEQC and TOUGHREACT programs for consistency with experiments. The thermodynamic conditions and the geofluid-rock-CO2 interactions prevent the mineralization of CO2 in the reservoir. This outcome differs from CarbFix projects in terms of the carbonization process, but the CO2 injection is still reliable with solubility-trapping in a geothermal reservoir to partially mitigate the emission. Roughly, 200 kt of CO2 in 10 years can be safely injected into the geothermal reservoir. According to the new analysis, the ratio of magnesium, sodium, and potassium varies in solid solution series of feldspars and clay minerals as albite end-member and montmorillonite/illite end-members, respectively. The evaluations of solid solution reactions are relatively limited in the law of mass action approach used by PHREEQC and TOUGHREACT.

A Multi-Task Learning Method for Relative Geologic Time, Horizons, and Faults With Prior Information and Transformer

Horizon extraction and fault detection are essential in seismic interpretation and closely related to each other. Most existing methods tend to deal with these two tasks independently, and may not work well in interpreting seismic images with complex geologic structures. We propose a multi-task learning (MTL) network with two branches to extract all horizons and detect faults simultaneously by estimating a relative geologic time (RGT) map as well as computing a fault map. These two branches share training datasets, feature maps, and network parameters during the training. The RGT estimation branch, constructed with a transformer architecture, is more lightweight compared to previous CNN methods but provides a larger and structure-oriented receptive field to adaptively capture global structural information for estimating a globally optimal RGT map. The fault detection branch is a simple convolutional neural network (CNN) which merges feature maps shared by the transformer and the derivatives of the estimated RGT to compute a fault map. The fault detection branch provides boundary control for the RGT estimation branch while the later provides global constraints for the former to improve its robustness to noise. Note that our RGT estimation by globally fitting all structures in a seismic image is a volumetric horizon interpretation method with which we are able to obtain a whole volume of horizons, all at once, by simply extracting contours of the RGT map. In our method, we further enable convenient human interactions by integrating manually interpreted horizons (or horizon segments) into the network, which imposes expert knowledge on the network to estimate reasonable RGT results from seismic images with complex fault systems, unconformities, and poor data quality. Moreover, when using 3D horizons as constraints, we are able to decompose the computationaly expensive 3D RGT estimation from a seismic volume into independently parallel 2D estimations slice by slice and combine them to obtain a laterally consistent 3D result.

A Local Iterative Approach for the Extraction of 2D Manifolds from Strongly Curved and Folded Thin-Layer Structures.

Ridge surfaces represent important features for the analysis of 3-dimensional (3D) datasets in diverse applications and are often derived from varying underlying data including flow fields, geological fault data, and point data, but they can also be present in the original scalar images acquired using a plethora of imaging techniques. Our work is motivated by the analysis of image data acquired using micro-computed tomography ([Formula: see text]) of ancient, rolled and folded thin-layer structures such as papyrus, parchment, and paper as well as silver and lead sheets. From these documents we know that they are 2-dimensional (2D) in nature. Hence, we are particularly interested in reconstructing 2D manifolds that approximate the document's structure. The image data from which we want to reconstruct the 2D manifolds are often very noisy and represent folded, densely-layered structures with many artifacts, such as ruptures or layer splitting and merging. Previous ridge-surface extraction methods fail to extract the desired 2D manifold for such challenging data. We have therefore developed a novel method to extract 2D manifolds. The proposed method uses a local fast marching scheme in combination with a separation of the region covered by fast marching into two sub-regions. The 2D manifold of interest is then extracted as the surface separating the two sub-regions. The local scheme can be applied for both automatic propagation as well as interactive analysis. We demonstrate the applicability and robustness of our method on both artificial data as well as real-world data including folded silver and papyrus sheets.

Nowcasting earthquakes in Iran: A quantitative analysis of earthquake hazards through natural times

Despite the extremely complex earthquake generation mechanism in a driven nonlinear threshold system, simple empirical scaling laws apply to the collective behavior of earthquakes in a network of geological faults. The physical interpretation of these properties and associated relations exhibit a wealth of information to study earthquake processes and consequent earthquake hazards in a defined area. In this article, an area-source-based earthquake nowcasting method is implemented to statistically determine the current state of earthquake hazards at several cities of Iran through the formulation of a discrete time-series of cumulative interevent counts, known as natural times. Use of natural times to mark the evolution of the seismic process, rather than the passage of clock time, essentially provides spatiotemporal and clustering invariable properties. Statistical inference of natural time counts corresponding to M ≥ 6.0 events results in an earthquake potential score (%) as Ahvaz (94), Hamadan (50), Isfahan (98), Karaj (76), Kerman (78), Kermanshah (73), Mashhad (40), Qom (92), Rasht (21), Shiraz (98), Tabriz (45), Tehran (78), Urmia (51), and Zahedan (53). These nowcast values provide a snapshot of the current progression of a city in its earthquake cycle of large-sized events and thus facilitate better decision-making, city-planning, and earthquake awareness, leading to an efficient seismic risk reduction strategy in the densely populated study region.

The applications of hyperspectral remote sensing techniques in the identification of subsurface faults. An experimental study

The study shows that geological faults can be identified by hyperspectral remote sensing techniques. The study was carried out at the Balapur fault, the longest evident fault in the Kashmir valley, NW Himalaya. The results indicate that the faults constitute a good oxidation and reduction environment, which causes some mineral elements in the soil to undergo oxidation and reduction reactions. The absorption features at the strike of the fault are typical of Fe3+ and Fe2+ and the soil spectrum across the fault is different and can be separated by clustering and discrete wavelet transform.

Magnetic and gravity modeling and subsurface structure of two geothermal fields in the UAE

There are two low-enthalpy geothermal systems along the eastern border of the United Arab Emirates: Ain Khatt (Khatt City, Ras Al Khaimah Emirate) and Green Mubazzarah–Ain Faidha (GMAF) (Al-Ain City, Abu Dhabi Emirate). The hot springs are likely to be meteoric waters fed through deep-seated faults that intersect the geothermal reservoirs at 2.6–3.8 km depth. Gravity and magnetic data were analyzed by gradient (horizontal derivative “HD”, and improved normalized horizontal tilt angle “INH”), and separately 3D modeled to image the subsurface structure of the two UAE geothermal systems. Bouguer anomalies in GMAF and Ain Khatt range from − 14.2 to 8.09 mGal and − 169.3 to − 122.2 mGal, respectively. Magnetic intensities in GMAF and Ain Khatt vary from 39,327 to 44,718 nT and 43,650 to 44,653 nT, respectively. The UAE hot springs (GMAF and Ain Khatt) are located in mainly high HD and INH regions, which reflect significant discontinuities in the basement rock, such as faults or lithological contacts. A joint inversion of magnetic and gravity data, through Artificial Neural Network (ANN) modeling, was performed to explore and interpret the 3D density and magnetic susceptibility variations. Results show that the hot springs in both geothermal systems are associated with intersecting geological contacts and fault zones. The Green-Mubazzarah–Ain Faidha hot springs may be connected at depth.

Underground Water Level, Strain, and Tilt Changes Observed Around the Fault Near Tono Research Institute of Earthquake Science

Near the Tono Research Institute of Earthquake Science (TRIES), Mizunami City, Gifu, two 500 m- deep shafts with diameters of 4.5 m and 6.5 m were excavated by the Japan Atomic Energy Agency (JAEA). The 6.5 m shaft is crossed by an NNW-trending geological fault (NNW fault), which has a right-lateral strike-slip component and a dip-slip component. Since before the excavation TRIES has been performing observations by a comprehensive set of borehole crustal activity observation devices in deep boreholes and extensometers in a vault near the shafts to observe variations in, for example, strain, tilt, and groundwater level continuously. During the shaft excavation, groundwater inflow to the shafts was encountered. The water was twice pumped out. During the pumping and non-pumping periods, TRIES’s observation data such as the groundwater level, the strain, and the tilt showed anomalous variations. The analysis of them revealed relationships among the groundwater level, the fault, the strain and the tilt. Strain analysis of TGR350 borehole station showed that the direction of the maximum shear strain was parallel to strike of the NNW fault. In addition, when the water in the shafts was being pumped out, the groundwater level at TGR350 declined and the maximum shear strain showed a right-lateral strike-slip movement in the NNW direction. When pumping was paused, the groundwater level increased, and the maximum shear strain showed a left-lateral strike-slip movement in the NNW direction. On the other hand, strain analysis of TGR165 borehole station showed different behavior from that of TGR350 borehole station deeper than TGR165. Tilt analysis of TGR165 borehole station showed tilt changes nearly perpendicular to strike of the NNW fault corresponding to the pumping and the non-pumping periods. Tilt analysis of TGR350 borehole station showed tilt changes of E-W direction with much smaller amplitude than that of TGR165. Behavior of the strain and the tilt during the pumping and non-pumping periods can be attributed in part to differences in the response of the medium to groundwater fluctuations, due to differences in the number and distribution characteristics of the fractures in the medium where the observation instruments are installed. We also discussed the observation results from the viewpoint of poroelasticity.

Numerical investigations to assess ground subsidence and fault reactivation during underground coal gasification

Abstract. This paper aims to assess potential environmental impacts associated with commercial-scale application of in situ coal conversion in a target area in Hungary. The site is an environmentally protected forested area. Parametric numerical modelling techniques were employed using a discrete element method (DEM) to evaluate the surface subsidence and fault activation during mining processes. The Mohr–Coulomb elastic–plastic material model adopted to simulate rock formations. Zero-thickness interfaces with friction and cohesive characteristics were employed to simulate geological faults. A sensitivity study on rock formations and fault properties was conducted to address the importance of geological parameters that have an impact on surface subsidence as well as fault activation, which could in turn result in pollutant migration from the deep coal seams to the surface. The analysis of the results demonstrated that surface subsidence is affected by the average Young's modulus of the geological strata, whereby the activation of the faults is influenced by the friction angle between faults. Also, it was found that shallower seams are more likely to produce surface subsidence; i.e. as excavation depth increases, the surface subsidence decreases. Finally, computational outputs from this work were used to develop the web-based and interactive Environmental Hazards and Risk Management Toolkit (EHRM) for planning and decision-making processes during in situ coal conversion.

Practical remote sensing data analysis for efficient geological field mapping: An example from the southwest portion of the Three Peaks 7.5ʹ quadrangle, southwest Utah

ABSTRACT We present the results of remote sensing analysis of U.S. Geological Survey digital elevation models, Landsat spectral data, and National Agriculture Imagery Program orthophotos to generate a preliminary geologic map that significantly aided our boots-on-the-ground geologic mapping of the southwest portion of the Three Peaks 7.5ʹ quadrangle in southwest Utah. Sedimentary rocks, intrusive rocks, and a variety of geologic contacts, including unconformities and faults, as well as unconsolidated alluvium are recognized in the study area. We constructed a series of geologic maps using remote sensing data and analysis techniques that are readily available to geoscientists. These techniques include band-ratioing, random forest analysis, and these analyses. Resolution of the resulting geologic maps generated by random forest analysis and principal component analysis were greatly improved by incorporating both the high resolution orthophoto and the 1/3 arc second digital elevation model into the principal component analysis. Our final remotely sensed geologic map integrated results from each technique. We used this remotely sensed geologic map to develop our preliminary plan for the field campaign. We preselected high priority targets (e.g., previously unrecognized units and faults) for in-person field analysis. We also identified highly accessible areas that allowed for efficient use of in-person field time needed for evaluation of large areas covered by relatively homogeneous units. The authors spent 25 days in the field over a seven-week field season, mapping the same area. Here, we compare the remote-sensed geologic maps with the final in-person field checked geologic map and discuss the utility of remote sensing data for detailed geologic field investigations. Preparing a remote sensing geologic map prior to field work has several advantages, including identification of mappable units, recognition of geologic contacts, and selection of priority target areas for direct evaluation of hypothesized field relationships, thereby promoting more efficient geologic mapping.

Crustal Structure of the Chuan‐Dian Block Revealed by Deep Seismic Sounding and its Implications for the Outward Expansion of the East Tibetan Plateau

AbstractThe Chuan‐Dian Block (CDB) is located in the southeastern margin of the Tibetan Plateau, with a complex geological structure and active regional faults. The present tectonic condition with strong crustal deformation is closely related to the ongoing collision of the India and Eurasia plates since 65 Ma. The study of the crustal structure of this area is key to revealing the evolution and deep geodynamics of the lateral collision zone of the Tibetan Plateau. Deep seismic sounding is the most efficient method with which to unravel the velocity structure of the whole crust. Since the 1980s, 19 deep seismic sounding profiles have been captured within the CDB area. In this study, we systematically integrate the research results of the 19 profiles in this area, then image the 3D crustal velocity, by sampling with a 5 km spacing and 2D/3D Kriging interpolation. The results show the following. (1) The Moho depth in the study area deepens from 30 km in the south to 66 km in the north, whereas there is no apparent variation from west to east. The Pn wave velocity is higher in stable tectonic units, such as 7.95 km/s in the Lanping‐Simao block and 7.94 km/s in the western margin of the Yangtze block, than in active or mobile tectonic units, such as 7.81 km/s in the Baoshan block, 7.72 km/s in the Tengchong block and 7.82 km/s in the Zhongdian block. (2) The crustal nature of the Tengchong block, the northern Lanping‐Simao block and the Zhongdian block reflects a type of orogenic belt, having relatively strong tectonic activities, whereas the crustal nature of the central Lanping‐Simao block and the western margin of the Yangtze block represents a type of platform. The different features of the upper‐middle crust velocity, Moho depth and Pn wave velocity to both sides of the Red River fault zone and the Xianshuihe fault zone, reflect that they are clearly ultra‐crustal. (3) Based on the distribution of the low velocity zones in the crust, the crustal material of the Tibetan Plateau is flowing in a NW–SE direction to the north of 26°N and to the west of 101°E, then diverting to flowing eastwards to the east of 101°E.

North slope transition zone of Songnan-Baodao sag in Qiongdongnan Basin and its control on medium and large gas fields, South China Sea

Based on analysis of newly collected 3D seismic and drilled well data, the geological structure and fault system of Baodao sag have been systematically examined to figure out characteristics of the transition fault terrace belt and its control on the formation of natural gas reservoirs. The research results show that the Baodao sag has the northern fault terrace belt, central depression belt and southern slope belt developed, among them, the northern fault terrace belt consists of multiple transition fault terrace belts such as Baodao B, A and C from west to east which control the source rocks, traps, reservoirs, oil and gas migration and hydrocarbon enrichment in the Baodao sag. The activity of the main fault of the transition belt in the sedimentary period of Yacheng Formation in the Early Oligocene controlled the hydrocarbon generation kitchen and hydrocarbon generation potential. From west to east, getting closer to the provenance, the transition belt increased in activity strength, thickness of source rock and scale of delta, and had multiple hydrocarbon generation depressions developed. The main fault had local compression under the background of tension and torsion, giving rise to composite traps under the background of large nose structure, and the Baodao A and Baodao C traps to the east are larger than Baodao B trap. Multiple fault terraces controlled the material source input from the uplift area to form large delta sand bodies, and the synthetic transition belt of the west and middle sections and the gentle slope of the east section of the F12 fault in the Baodao A transition belt controlled the input of two major material sources, giving rise to a number of delta lobes in the west and east branches. The large structural ridge formed under the control of the main fault close to the hydrocarbon generation center allows efficient migration and accumulation of oil and gas. The combination mode and active time of the main faults matched well with the natural gas charging period, resulting in the hydrocarbon gas enrichment. Baodao A transition belt is adjacent to Baodao 27, 25 and 21 lows, where large braided river delta deposits supplied by Shenhu uplift provenance develop, and it is characterized by large structural ridges allowing high efficient hydrocarbon accumulation, parallel combination of main faults and early cessation of faulting activity, so it is a favorable area for hydrocarbon gas accumulation. Thick high-quality gas reservoirs have been revealed through drilling, leading to the discovery of the first large-scale gas field in Baodo 21-1 of Baodao sag. This discovery also confirms that the north transition zone of Songnan-Baodao sag has good reservoir forming conditions, and the transition fault terrace belt has great exploration potential eastward.

Impact of past mining on public safety: seismicity in area of flooded abandoned coal Gardanne mine, France

This paper focuses on the impact of past mining on public safety. It emphasizes the need to understand the induced seismic hazard and consequently improve the post-mining management procedures and legislations, as many mining sites are located in proximity to populated areas. Due to many challenges and complexity of the post-mining environments, induced seismic hazard nowadays remains largely unknown. However, the return experience of several post-mining sites in recent decades have shown us that the mine flooding and/or degradation of mining works can lead to the stress perturbations, inducing the seismicity and the reactivation of the surrounding geological faults. Hence, it is important to advance the seismic monitoring and research of seismicity in flooded post-mining districts. As the number of mine closures worldwide is rising, it can be expected that flooding induced reactivation of the surrounding faults becomes a more often observed phenomenon. We present in this paper the experience of the abandoned flooded coal mine of Gardanne in France, which has been experiencing post-mining seismicity problems since its closure in 2010. We show the results of a recent study of seismic multiplets and clustering of seismic events, as well as their spatio-temporal activity compared to meteorological conditions. These results provide us new insights as well as lead to raising new questions on seismic sources and triggering mechanisms.

Seismic Performance Evaluation of a Multi Storey RC Structure Subjected to Strong Ground Motions

Abstract: A tremor or a movement of the ground occurs during an earthquake on Earth's surface. Earthquakes can also cause landslides and volcanic eruptions. Natural disasters or human activity can produce earthquakes, which are defined as seismic events generating seismic waves. Earthquakes most commonly occur when geological faults rupture, however they can also occur as a result of volcanic eruptions, landslides, mine explosions, and nuclear testing. The study of structural behavior towards different ground motions is therefore one of the main criteria to determine damage intensity. Structural Analysis of a residential building is carried out by using ETabs Software. Present study is intended to study the dynamic behavior of Multistorey Reinforced Concrete structure by considering, an existing G+13 storey residential building is modeled and its structural behaviour is studied using Time history method by considering different high intensity earthquakes. The behaviour of the building is studied mainly for its base shear, Storey displacement and maximum joint displacement.

The Usage of GIS Tools on Vintage Aerogeophysical Data for Simple and Fast Processing with a Focus on Fault Interpretation: An Austrian Case Study

The reuse of vintage datasets which were acquired in the 20th century can pose challenges for modern geophysical modeling due to missing detailed preprocessing information, significant uncertainties, or lack of precise tracking, etc. Nevertheless, they are often the only available datasets in a target region. We explore here the potential of such vintage airborne geophysical datasets (magnetics, AEM, radiometrics) to detect the location and dip direction of geological faults, using a non-modeling interpretation approach based on multiple GIS tools. We apply our approach in a geologically well-known region where four different types of faults are mapped. The applicability of the tools used in this study depend on the geological setting of each fault and is evaluated based on the comparison with geological and—where available—with modeling data. In general, the GIS tools, especially used on a combination of datasets, show reliable results concerning the location and strike of faults, and even seem to be able to predict the dip direction of a fault.