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Strike and dip are essential to the description of geological features and therefore play important roles in 3D geological modeling. Unevenly and sparsely measured orientations from geological field mapping pose problems for the geological modeling, especially for covered and deep areas. This study developed a new method for estimating strike and dip based on structural expansion orientation, which can be automatically extracted from both geological and geophysical maps or profiles. Specifically, strike and dip can be estimated by minimizing an objective function composed of the included angle between the strike and dip and the leave-one-out cross-validation strike and dip. We used angle parameterization to reduce dimensionality and proposed a quasi-gradient descent (QGD) method to rapidly obtain a near-optimal solution, improving the time-efficiency and accuracy of objective function optimization with the particle swarm method. A synthetic basin fold model was subsequently used to test the proposed method, and the results showed that the strike and dip estimates were close to the true values. Finally, the proposed method was applied to a real fold structure largely covered by Cainozoic sediments in Australia. The strikes and dips estimated by the proposed method conformed to the actual geological structures more than those of the vector interpolation method did. As expected, the results of 3D geological implicit interface modeling and the strike and dip vector field were much improved by the addition of estimated strikes and dips.

A multi-layer perceptron (MLP) technique is used to train on the response spectra for various strike angles, dip angles, and rake angles. Fixing the magnitude and depth of the earthquakes, the 3-component ground motion is simulated with the help of SPECFEM3D. The residuals of spectral acceleration as a function of time period, for low-rise to high-rise structures, are found to be free of any trend. The hidden layers in the MLP learn the interdependency of focal mechanism parameters on the response spectrum. The resultant model was checked for attenuation characteristics with respect to distance. Furthermore, the trained MLP also showed a shift in spectral peak due to radiation damping, as expected. This MLP architecture presented in this work can be broadly extended to predict the response spectrum, at bedrock level, for any focal mechanism parameters, i.e., strike, dip, and rake, depending on the velocity model of that region.

Mixture density networks (MDNs) are a class of neural network algorithms in the Bayesian framework that can invert for parameters and estimate the parameter uncertainties at the same time. We test MDNs by inverting the fault geometric parameters in a synthetic test with Okada’s model and demonstrate the efficiency and robustness of the model. To further describe the MDNs algorithm, we invert regional static GPS displacement data for the 2013 Ms7.0 Lushan Earthquake in China to obtain the fault geometric parameters. The inverted geometric parameters, which are in the form of distributions, agree well with the published solutions for this event once the 99.7% confidence interval are taken into account. The 99.7% confidence intervals of the strike and dip angles are [ $$187.5^\circ$$ , $$220.4^\circ$$ ] and [ $$20.76^\circ$$ , $$49.76^\circ$$ ], respectively. To demonstrate the applicability of the inverted geometric parameters, we invert the slip distribution of the Lushan earthquake with the inverted parameters and GPS displacements. From the slip distributions considering the distributions of the parameters, we obtain the 99.7% confidence intervals of the magnitude Mw, maximum slip and depth of maximum slip, which are [6.51, 6.65], [0.30, 0.74] m and [9.43, 13.61] km, respectively.

One of the main problems related to mature oilfields is the decreased pore pressure due to hydrocarbon production. Therefore, to maintain the production rate of a reservoir, the lost pressure must be compensated. A very traditional method to increase the pressure is to inject natural gas into the reservoir. This technique is widely used in SW Iranian reservoirs because of the readily available supply of this type of gas. Reactivation of pre-existing faults and inducing new fractures into the reservoir and cap rock are some of the potential risks regarding gas injection. In this article, using data such as well logs, pore pressure estimates, and rock mechanical test results, the geomechanical simulation of the Asmari reservoir in the Gachsaran oilfield, SW Iran has been carried out. For this purpose, the current stress field was determined using elastic moduli of reservoir rocks and formation integrity test (FIT) results. Then, by applying analytical methods such as Mohr diagrams and slip tendency, the reactivation possibility of four faults in the field was analyzed, and the maximum sustainable pore pressures were estimated. In the next step, numerical simulations were conducted using ABAQUS software to investigate the injected gas flow path, leakage potential through the cap rock, possible fault reactivation due to gas injection, and shear stress build-up and plastic strain development in different parts of the reservoir. Results of Mohr diagrams and slip tendency showed that all the faults are stable in the current stress state, and fault F2 has the potential to sustain a maximum pore pressure of 55 MPa in the field. On the other hand, fault F3 has the proper conditions (i.e., strike and dip referring to σHmax orientation) for reactivation. Results of numerical simulations suggested that an injection pressure of 30 MPa would not induce any new fracture or fault slip within 5 years of injection. In this period, the injected gas plume moves upward through the damage zone and reaches the shallower parts of the cap rock. It was also shown that by applying an injection pressure of 60 MPa, slip would occur on fault F4 after 10 days of injection.

Mining of multiple coal seams and sections is the main method adopted by the vast majority of coal mines in China at present. However, because of multiple mining, the damage and deformation of surrounding rock increases a lot when comparing with single coal seam mining. Moreover, the normal production and safety of coal mine may also get affected. In multiple coal seam mining, the distribution and alteration of mining induced stress are the main reasons of the above problems. In this study, based on the geological conditions and mining design of Weijiagou Coal Mine, the mining induced stress under multiple mining conditions were studied. According to the failure state, the surrounding rock was divided into the damaged zone, plastic zone and elastic zone. The distribution and range of mining stress in different areas were calculated by utilizing Strain Softening Model. Based on FLAC3D numerical simulation, the distribution and change of mining induced stress along the strike and dip direction of coal seam were obtained. By using the Logarithmic function and the Fourier function, the empirical formula of the relationship between the maximum mining stress in front of the working face and the advancing distance of the working face is obtained. This study provides a reference for the design of roadway support and mining face under multiple mining conditions.

Accessibility and inclusivity in field geology have become increasingly important issues to address in geoscience education and have long been set aside due to the tradition of field geology and the laborious task of making it inclusive to all. Although a popular saying among geologists is “the best geologists see the most rocks”, field trips cost money, time, and are only accessible to those who are physically able to stay outside for extended periods. With the availability of 3D block diagrams, an onslaught of virtual learning environments is becoming increasingly viable. Strike and dip is at the core of any field geologist's education and career; learning and practicing these skills is fundamental to making geologic maps and understanding the regional geology of an area. In this paper, we present the Strike and Dip virtual tool (SaD) with the objective of teaching the principles of strike and dip for geologic mapping to introductory geology students. We embedded the SaD tool into an introductory geology course and recruited 147 students to participate in the study. Participants completed two maps using the SaD tool and reported on their experiences through a questionnaire. Students generally perceived the SaD tool positively. Furthermore, some individual differences among students proved to be important contributing factors to their experiences and subjective assessments of learning. When controlling for participants' past experience with similar software, our results indicate that students highly familiar with navigating geographical software perceived the virtual environment of the tool to be significantly more realistic and easier to use compared with those with lower levels of familiarity. Our results are corroborated by a qualitative assessment of participants' feedback to two open-ended questions, highlighting both the overall effectiveness of the SaD tool and the effect of geographical software familiarity on measures of experience and learning.

Ambient seismic noise tomography is a novel, low-impact method for investigating the earth's structure. Although most passive seismic studies focus on structures on crustal scales, there are only a few examples of this technique being applied in a mineral exploration context. In this study, we performed an ambient seismic experiment to ascertain the relationship between the shallow shear wave velocity and mineralized zones in the Erzgebirge in Germany, one of the most important metal provinces in Europe. Late Variscan mineralized greisen and veins occurring in the Geyer-Ehrenfriedersdorf mining district of the Central Erzgebirge were mined from medieval times until the end of the 19th century. These occurrences represent a significant resource for commodities of high economic importance, such as tin, tungsten, zinc, indium, bismuth and lithium. Based on ambient noise data from a dense “LARGE-N” network comprising 400 low-power, short-period seismic stations, we applied an innovative tomographic inversion technique based on Bayesian statistics (transdimensional, hierarchical Monte Carlo search with Markov Chains using a Metropolis/Hastings sampler) to derive a three-dimensional shear wave velocity model. An auxiliary 3D airborne time-domain electromagnetic dataset is used to provide additional insight into the subsurface architecture of the area. The velocity model shows distinct anomalies down to approximately 500 m depth that correspond to known geological features of the study area, such as (a) gneiss intercalations in the mica schist-dominated host rock, imaged by a SW–NE striking low-velocity zone with a moderately steep northerly dip, and (b) a NW-trending strike-slip fault, imaged as a subvertical linear zone cross-cutting and offsetting this low-velocity domain. Similar to the velocity data, the electromagnetic data exhibit north-dipping (high-conductivity) structures in the mica schists, corresponding to the strike and dip of the predominant metamorphic fabric. An unsupervised classification performed on the bivariate 3D dataset yielded nine spatially coherent classes, one of which shows a high correspondence with drilled greisen occurrences in the roof zone of a granite pluton. The relatively high mean shear velocity and resistivity values of this class could be explained by changes in density and composition during greisen formation, as observed in other areas of the Erzgebirge. Our study demonstrates the great potential of the cost-efficient and low-impact ambient noise technology for mineral exploration, especially when combined with other independent geophysical datasets.

Kashmir earthquake of October 8, 2005, was the most devastating in the recent history of South Asia, causing more than 86,000 casualties, and was accompanied by numerous slope failures. Like many other earthquakes hitting the rugged mountainous terrains of developing countries, strong ground motion records of Kashmir earthquake were also deficient. In the absence of waveforms, source inversion analysis of the geodetic data is performed to reveal spatial distribution of slip on a 90 km × 30 km fault rupture plan with dip and strike angles of 29° and 320°, respectively. The largest asperity, having a maximum slip value of 7.5 m, has appeared at the same location where the large crustal deformation was detected. The slip distribution pattern near the ground surface is consistent with the crustal deformations. Also, seismic stresses are calculated for the epicentral areas for a stratified half-space through forward modeling. All the landslides triggered by Kashmir earthquake are spotted in the areas having high values of square root of the second principal invariant of deviatoric stress tensor ( $$\sqrt{{J}_{2}}$$ ), witnessing a relationship between co-seismic stresses and earthquake-induced landslides. This study will be helpful to rationally understand earthquake-induced damages, their scientific basis, and to establish a cause-and-effect relation between the seismic activity and damaged pattern which can be helpful for rehabilitation, disaster management, and preparedness for future seismic disasters.

A new interpretation of the 2016 Meinong earthquake is proposed based on the Synthetic Aperture Radar (SAR) satellites, high-rate GPS and strong motion data. The fault geometry is firstly estimated by the Interferometric Synthetic Aperture Radar (InSAR) surface deformation data. Then, the coseismic rupture process is inferred through the 1-Hz GPS and strong motion data based on the estimated fault geometry parameters. The InSAR-derived best-fitting fault geometry model suggests that the preferred fault strike and dip angles are 271.7° and 22.7°, respectively. The inferred fault rupture model indicates that the coseismic fault rupture is a mixed motion of thrust and left-strike slip with the maximum slip of ~ 1.0 m, and the high slip area is located at 9–16 km underground. The snapshots demonstrate that the coseismic fault rupture propagation is along the northwest direction, with the entire duration of ~ 16 s. Besides, the InSAR-derived faulting model reflects that the InSAR observation includes the deformation caused by aseismic slip and aftershock. However, the InSAR-derived fault geometry model can significantly contribute to the estimation of the rupture process based on the high-rate GPS and strong motion data.

Deformation resulting from slip on a fault plane creates stress changes in the surroundings. The stress change formulated in the Coulomb stress equation has been used to explain this type of seismic interaction. However, the sensitivity of the input parameters needs to be assessed, including the earthquake source fault geometry and the regional stress. Range analysis based on the Taguchi orthogonal array has been widely used in experimental designs to analyze the result sensitivity based on the parameters. In this study, we incorporate the Taguchi orthogonal method to analyze the sensitivity of static Coulomb stress transfer in relation to the source fault geometry and the regional stress magnitude. The 2016 Pidie Jaya, Aceh earthquake (Mw = 6.5) in Indonesia, was used as a case study. Our sensitivity result shows that the dip and strike of the source fault are the first and second parameters that have the most effect on the distribution of static Coulomb stress transfer. We, thus, used additional constraint to model these parameters, i.e., the Pidie Jaya earthquake aftershocks which were obtained from a dense local seismic network. Using the updated input model, we conducted Pidie Jaya earthquake static Coulomb stress modeling. The stress results show a better agreement between positive stress change and the aftershock distribution.

Fault interpretation is a key step for seismic structural interpretation and reservoir characterization. In conventional approach, faults are identified as reflection discontinuity or abruption in post-stack seismic data. In order to highlight fault, several fault attributes by measuring waveform similarity or diversity have been proposed. However, noise and stratigraphic features can also be highlighted in a fault attribute image. We propose a forward and backward diffusion method to enhance the fault image so that the noisy features which unrelated to faults are suppressed and the fault features are sharpened. We first estimate the planarity (linearity in 2D) and fault orientation (strike and dip) of every sample in fault image by using a PCA-based algorithm. Combining the planarity and fault orientation, we then construct fault probability map based on the assumption that faults can be seemed as relatively steep planes in a small spatial window. Thanks to the fault probability map, we can adaptively switch the diffusion process from a forward mode to a backward mode. Forward diffusion force is used to suppress the non-fault features within the low fault probability area and backward diffusion force is used to enhance the fault features within the high fault probability area. A real 3D example is included to demonstrate that this method can effectively suppress the noise and sharpen the faults. Furthermore, automatic fault tracking on an enhanced fault image can get more accurate result than on an original fault image.

Surrounding rock control is problematic at irregular fully-mechanized working faces of inclined seams. This study investigated the evolution of mining-induced stress at a variable-length working face under different coal seam inclination angles by using FLAC3D software to establish an experimental model based on the occurrence conditions of the inclined seam and the layout of fully-mechanized working face in the western district of Pan’er mine in China. Analysis of the simulation data was used to determine the stress evolution of working face in the strike and dip directions under different dip angle conditions and reveal the relationship between mining stress evolution and coal seam inclination. Comparative analysis of the formation and evolution of mining-induced stress before and after the roadway connection was used to determine the mechanisms behind mining-induced stress evolution in the short face to long face connection process and to reveal asymmetrical differences in the mining-induced stress evolution of the upper, middle and lower parts of the coal seam along the dip direction. Based on the relationship between supports and surrounding rock, the structure of hydraulic powered supports, the entry arrangement and supporting characteristics, control methods to ensure the stability of surrounding rock are proposed such as a metal mesh above hydraulic powered supports and reinforcement at the junction. These measures are effective for preventing partial roof fall and rib spalling, loss of support stability and stress concentration at connecting entry and for achieving safe and efficient mining of irregular working faces in thick inclined seams.

Geology information has an important role in development planning in Indonesia especially in physical development so that it needs to be well laid out in order to give the complete information. The objectives of the study are: First, integrating result of the SAR technique processing to image fusion technique to identify geological structure, landform and litology in Pidie Jaya region, Aceh province and Second, testing ability of SAR technique and image fusion technique in geology reconstruction in Pidie Jaya region. This study was done in most parts of Pidie Jaya and Pidie region using the main data that were Sentine-1A with VH polarization and Landsat 8 OLI with 567 composite. The methods used are digital image processing and field observation. Digital image processing uses some techniques including: SAR technique (calibration, multilook, deburst, median speckle filtering, geometric correction), InSAR tecnique to create DEM, HSV image fusion and directional spatial filter techniques (3x3 and 5x5 windows) to identify landform, geological structure and litology through visual interpretation. Field observation was done through strike and dip measuring with purposive sampling method. Results of HSV fusion technique visual interpretation can identify structural landform, volcanic landorm, fluvial landform, drainage patterns and litology. Results of directional filter visual interpretation can identify lineament, fault and fold. Geological structure in study region has dominant direction South West – North East or 42.4 o – 223.63 o . The study region is dominated by structural landform with an area of 555.39 km 2 or 59.56 % of study area total with accuration 86.04 %. Litology which dominates in study area is sandstone with an area of 571.78 km 2 or 61.31 % of study area total with accuration 82.93 %.

Knowing the current condition of the faults and fractures in a reservoir is crucial for production and injection activities. A good estimation of the fault reactivation potential in the current stress field is a useful tool for locating the appropriate spot to drill injection wells and to calculate the maximum sustainable pore pressure in enhanced oil recovery and geosequestration projects. In this study, after specifying the current stress state in the Gachsaran oilfield based on Anderson’s faulting theory, the reactivation tendency of four faults (F1, F2, F3, and F4) in the Asmari reservoir is analyzed using 3D Mohr diagrams and slip tendency factors. Results showed that all the faults are stable in the current stress state, and F2 has the potential to undergo the highest pore pressure build-up in the field. On the other hand, F3 has the proper conditions (i.e., strike and dip referring to σ Hmax orientation) for reactivation. Stress polygons were also applied to show the effect of the pore pressure increase on fault stability, in a graphical manner. According to the results, the best location for drilling a new injection well in this part of the field is the NW side of F2, due to the lower risk of reactivation. It was found that both methods of 3D Mohr diagrams and slip tendency factors predict similar results, and with the lack of image logs for stress orientation determination, the slip tendency method can be applied. The results of such studies can also be used for locating safe injection points and determining the injection pressure prior to numerical modeling in further geomechanical studies.

Assessment of discontinuity controlled failure phenomena over large areas is extremely hard or even impossible due to the difficulties encountered at the data collection stage. Conventionally, the data collection has been made by engineering geologists via field surveys using compass and measurement tapes. The present study proposes a new low-cost and practical approach by using mobile phones and photogrammetric methods, which allows the measurement of orientation (strike and dip) of discontinuity in a computerized environment. The images acquired using a smartphone camera provide the means for highly representative surface modeling via dense image matching. Such dense measurements reduce the errors caused by sparse sampling of discontinuity surfaces. The kinematic analysis based on the orientation data obtained from the proposed methodology shows the discontinuity controlled failure susceptibility. The methodology proposed here has been applied to a part of Ihlara Valley in Cappadocia Region (Central Turkey), which has columnar structures that are extremely difficult to survey with conventional field works. The application of the proposed methodology yields successful and promising results for large and inaccessible terrain types. Although a major improvement to the proposed methodology would be using the geolocation and rotation of the images obtained from the sensors of the phone directly (thus eliminating the need for external control points with known ground coordinates), the procedure described in this study is low-cost and do not require extensive knowledge on photogrammetry for engineering geologists.

The peculiarities of the structure of Cretaceous–Eocene boundary deposits in the Belogorsk district, Central Crimea, are considered. Tectonic structures interpreted as paleoseismodislocations are revealed and described; their age, structures, and evolutionary history are characterized; the magnitude and intensity of the seismic paleoevent are estimated. The position of steeply dipping fractures in Cretaceous rocks is regular and related to the bedding along the dip and strike of the structure. Their formation was caused by transverse extension in the background of general uplift at the beginning of Eocene, coincided in time with the main folding phase in North Turkey.

The article considers features of boundary Cretaceous–Eocene deposits in Belogorskiy district of Central Crimea. Structures interpreted as paleoseismic dislocations are described, their age, features of composition, history of formation are specified, magnitude and intensity of paleoearthquake are estimated. Steeply dipping fractures in Cretaceous rocks are regular and associated with dip and strike of the main regional structures. Their formation was caused by a transverse stretching during the main uplift of the structures at the beginning of the Eocene coinciding with the main phase of folding in Northern Turkey.

Dyke intrusion is a highly dynamic process with seismicity preceding and accompanying magma emplacement on timescales of hours to days. Recent surveys of microseismicity indicate shear failure along fault planes parallel to the orientation of intruding dykes. However, the precision of earthquake hypocentre locations is typically limited to tens or hundreds of meters and cannot resolve whether the hypocentres relate to strain of wall rock fragments within the dykes, fault damage around the intrusions or peripherally in the country rock. Here we present high-resolution three-dimensional (3D) reconstructions of outstanding coastal exposures of a swarm of 19 dolerite dykes, near Albany, Western Australia using an unmanned aerial vehicle and Structure-from-Motion photogrammetry. It is observed that the number of faults and joints increases towards the dyke swarm, which, alongside mutually overprinting relationships, indicate that dyke emplacement and faulting were coeval. The faults contain cataclasites and are parallel to the dykes. In contrast, Mohr–Coulomb theory predicts shear failure on strike-parallel faults inclined ∼30° to the dyke plane. The faults and joints form a damage zone associated with the dyke swarm, even though the dykes themselves occupy Mode I extension fractures. These results confirm the recent geophysical evidence for dyke-parallel shear failure that can occur in the host rocks around intruding dykes. We suggest that coeval dyke-parallel seismicity both reactivated existing fracture networks and nucleated new fractures. Based on the premise that host-rock fracturing induces changes in elastic properties, remote stresses can reorientate locally leading to shear failure. This model provides for the first time an explanation for the origin of double-couple failure that is parallel in 3D (strike and dip) to dykes during their emplacement.

We relocate earthquakes occurring 1 week before and 1 month after the 2016 Yunlong Ms5.0 earthquake by simultaneously using P (and S) travel times and waveform cross-correlation data in the double-difference relocation algorithm. We then use the well-relocated earthquakes as template events and scan through the continuous waveforms to search for and locate weak events by using the match and locate method. A total of 4602 events are detected by using 660 templates, which is ~ 3 times the number of events listed in the Yunnan Seismic Networks catalogue. Our refined catalogue reveals three stages of seismic activity and energy release processes during the 2016 Yunlong Ms5.0 earthquake sequence. We also refine the focal depths and mechanisms of 12M ≥ 3.0 earthquakes using the broadband waveform modeling method. Both the relocated hypocenters and focal mechanisms of the 12M ≥ 3.0 earthquakes delineate fault strike and dip angles of ~ 200° and ~ 75°, respectively, indicating that the seismogenic fault could be a NNE-striking blind or subfault located between the Weixi-Qiaohou Fault and Lancangjiang Fault. Our results could contribute to better understanding of local seismic hazard evaluations in the vicinity of Yunlong area of Yunnan, China.

Ground-based, time-domain electromagnetic, magnetic and gravity datasets were obtained for the southern-section of the Gurubang VHMS deposit located approximately 15 km east of Cooma, NSW. The Gurubang deposit is hosted in a mid-late Silurian sequence of rock composed of shallow marine sediments and felsic volcanic rocks. The aim of this research was to ascertain the usefulness of high-resolution geophysical techniques in targeting and evaluating a small-scale polymetallic massive sulphide deposit, and to investigate how the detailed geophysics relates to the overall geological framework of the prospect area. The acquired data was analysed using a forward modelling approach. Due to the deposits high concentration of conductive minerals, a coincident loop time-domain electromagnetic 2D survey effectively delineated the sulphide mineralisation, and was useful in interpreting and adapting deposit parameters such as the azimuth, dip and strike length. Based on the physical nature of the target deposit, it was determined that high-resolution magnetic and gravity surveys would not be effective methods in directly delineating these smaller-scaled (10’s of m’s) mineral deposits. However, magnetics and gravity did prove effective in depicting the surrounding geology, including potential volcanic intrusions and basement lithologies and structures.

Fast-tracked by need for field trip alternatives during the Covid-19 pandemic, the Strike and Dip (SaD) tool uses structure from motion 3D models of rocks in a virtual environment to facilitate teaching students how to measure the orientation of rock faces, necessary for the completion of geologic maps. Spatial reasoning is a difficult skill to master for geology students, although a significant component of their studies involves visualising 3D structures from 2D representations, in particular, maps. More time and experience is necessary for students to practice their spatial reasoning skills, but this is a logistical challenge. The SaD tool provides an interface that resolves these logistics of practice time and field site access. Geology is often first characterised as a field science, but recent and increasing efforts to make a more inclusive environment have shown a demand to establish a comprehensive alternative to fieldwork/trips. The SaD tool is malleable, and while providing an inclusive way to teach core components, it is also capable of an array of field experiences for almost every sub-field within the geosciences. In this pilot study, introductory geoscience students were assigned a geologic mapping lab using the SaD tool. Results overall were positive in regard to the usefulness of the tool and provide us with three main directions for next steps in research and development.

To design underside protective seam strip layout. Similarity model experiments, numerical simulations and theoretical calculations are used to quantitatively study the pressure relief protection effect of different strip widths, dip angles and coal pillar widths of a thin underside protective seam under deeply buried conditions. The optimal strip width range is obtained according to the change law of strain during the mining process of the underside protective seam in a similar model experiment. The change law of the expansion of the protected coal seam is obtained and the fitting surfaces among the dip angle and strip width of the coal seam with the protection distance and pressure relief angle along the strike and dip of the protected coal seam are established according to the numerical simulation results of underside protective seam mining. It is concluded that the best pressure relief effect can be achieved when the dip angle is 16.7° and the strip width is 70 m. According to the stability threshold of coal pillars considered in strip mining theory, the coal pillar width is calculated to be 50 m. Similarity model experiments and numerical simulations of protected coal seam mining verify the pressure relief effect of the designed protective seam strip width and pillar width. A calculation method of the protective seam strip width, position and pillar width required by the specific width of the protected seam is proposed.

Soils and rocks can undergo deformation and sedimentation processes, which are architectural, geological structures. The geological formation of an area generally refers to field observations and secondary data. Consideration has been carried out at two locations in Maros Regency, South Sulawesi Province, with the aim of the study being to determine the stress orientation in the area. This observation uses a geological compass to measure strike and dip shapes, which are then processed to produce a Rosette Diagram. Based on the Rosette diagram obtained, it can be concluded that the principal stress in the area has orientation around the northwest-southeast. It is suspected that the formation of fractures in the Maros Regency influenced by volcanism in the structure of the Camba formation. Furthermore, this geological information is expected to be used as a comparison in research related to geoscience.

An overlying rock structure plays a key role in controlling the roof deformation of nonpillar gob-side entry retaining by roof cutting. On the bases of the actual geological conditions of II 632 Haulage Roadway at the Hengyuan coal mine, a similar three-dimensional simulation experiment of roof precutting is conducted. Thereafter, the caving characteristics and migration law of the roof strata in the strike and dip directions are obtained. Moreover, the roof of the retained roadway and key strata of the goaf can form a hinge structure of the key blocks. By monitoring the deformation of the surrounding rock and stress distribution of the roof, the skew deformation characteristics of roadway roof are obtained. By observing the borehole peeping technology, the roof subsidence near the goaf is determined to be greater than that of the solid coal side, and the roof subsidence of the gob-side entry retained by roof cutting is greater than that of the floor heave and two sides approaching. Results of the three-dimensional similar simulation experiment indicate that the mechanical structure model of the key block of the retained roadway roof is constructed, and the mechanical analytical solution of the required support resistance of the retained roadway roof is obtained. This study proposes the constant resistance and large deformation anchor cable reinforcement support method to control the roof deformation of the retaining roadway. Through engineering application, the maximum value of the roof and floor movement of the retained roadway is stable at approximately 650 mm. The retained roadway can meet the demand of the next mining face.

In three-dimensional (3-D) implicit geological modeling, the bounding surfaces between geological units are automatically constructed from lithological contact data (position and orientation) and the location and orientation of potential faults. This approach was applied to conceptualize a karst aquifer in the Middle Triassic Muschelkalk Formation in southwest Germany, using digital elevation data, geological maps, borehole logs, and geological interpretation. Dip and strike measurements as well as soil-gas surveys of mantel-borne CO2 were conducted to verify the existence of an unmapped fault. Implicit geological modeling allowed the straightforward assessment of the geological framework and rapid updates with incoming data. Simultaneous 3-D visualizations of the sedimentary units, tectonic features, hydraulic heads, and tracer tests provided insights into the karst-system hydraulics and helped guide the formulation of the conceptual hydrogeological model. The 3-D geological model was automatically translated into a numerical single-continuum steady-state groundwater model that was calibrated to match measured hydraulic heads, spring discharge rates, and flow directions observed in tracer tests. This was possible only by introducing discrete karst conduits, which were implemented as high-conductivity features in the numerical model. The numerical groundwater flow model was applied to initially assess the risk from limestone quarrying to local water supply wells with the help of particle tracking., Eberhard Karls Universität Tübingen (1020)

High-strength mining of super-large coalfaces in the Shendong coalfield causes significant damage to the ground surface. To study the key parameters of undermined coalfaces that affect ground damage, 25 numerical simulation models were designed using an orthogonal experimental method based on the geological and mining conditions of the Bulianta Mine. In the orthogonal design, four factors (the lengths in both the dip and strike directions, the thickness and the mining speed of the coalface) were considered, with five levels designed for each factor. The subsidence displacements and deformations caused by the excavation were then simulated and verified using field surveying data. A damage extent index (DEI) was introduced and used to assess the extent of global ground damage caused by each simulative excavation. Analysis of variance (ANOVA) method was then employed to determine the key parameters of the coalface that significantly influence the ground damage. It was found that the coalface dip length and thickness and the coalface thickness can be regarded as the key parameters for ground objects of building and timberland, respectively. This research provides theoretical and technical support for the coordinated exploitation of resources and environments in Shendong and other similar, ecologically fragile coalfields.

Proper and rational borehole utilization in various aspects of prospecting and outlining of mineral deposits is undoubtedly a vital task. Geometric modeling and a widespread use of a CAD system could facilitate the solution of various mining, geological, and engineering problems. The geometric modeling of boreholes improves the process of prospecting and outlining of mineral deposits and supports their assignment to automation system of project planning. This research addresses one of the aspects of subsoil geometry associated with widespread use of computers to solve various mining-and-geological and engineering problems. A core pole provides various data about the geological structure of a blanket deposit gap. It reveals mechanical and structural properties of mineral deposits and helps to evaluate mineral reserves. To obtain this data a number of exploration holes is bored on a studied gap of a mineral deposit. The geometric modeling of boreholes is based on their approximation to the classic geometric images. From the geometric point of view, a borehole is a cylinder. Therefore, some positional and metric problems could be solved on a core pole using descriptive geometry. A developed algorithm and its mathematical formulation contribute to designing of a program for automatic problem solving and measuring of strike and dip using a core pole.

This study reports in-situ sedimentologic evidence of giant floods in Gale crater, Mars, during the Noachian Period. Features indicative of floods are a series of symmetrical, 10 m-high gravel ridges that occur in the Hummocky Plains Unit (HPU). Their regular spacing, internal sedimentary structures, and bedload transport of fragments as large as 20 cm suggest that these ridges are antidunes: a type of sedimentary structure that forms under very strong flows. Their 150 m wavelength indicates that the north-flowing water that deposited them was at least 24 m deep and had a minimum velocity of 10 m/s. Floods waned rapidly, eroding antidune crests, and re-deposited removed sediments as patches on the up-flow limbs and trough areas between these ridges forming the Striated Unit (SU). Each patch of the SU is 50–200 m wide and long and consists of 5–10 m of south-dipping layers. The strike and dip of the SU layers mimic the attitude of the flank of the antidune on which they were deposited. The most likely mechanism that generated flood waters of this magnitude on a planet whose present-day average temperature is − 60 °C was the sudden heat produced by a large impact. The event vaporized frozen reservoirs of water and injected large amounts of CO and CH from their solid phases into the atmosphere. It temporarily interrupted a cold and dry climate and generated a warm and wet period. Torrential rainfall occurred planetwide some of which entered Gale crater and combined with water roaring down from Mt. Sharp to cause gigantic flash floods that deposited the SU and the HPU on Aeolis Palus. The warm and wet climate persisted even after the flooding ended, but its duration cannot be determined by our study., With funding from the Spanish government through the "María de Maeztu Unit of Excellence" accreditation (MDM-2017-0737)

It has been suggested that a better knowledge of fault locations and slip rates improves seismic hazard assessments. However, the importance of detailed along‐fault‐slip‐rate profiles and variable fault geometry has not yet been explored. We quantify the importance for modeled seismicity rates of using multiple throw‐rate measurements to construct along‐fault throw‐rate profiles rather than basing throw‐rate profiles on a single measurement across a fault. We use data from 14 normal faults within the central Italian Apennines where we have multiple measurements along the faults. For each fault, we compared strain rates across the faults using our detailed throw‐rate profiles and degraded data and simplified profiles. We show the implied variation in average recurrence intervals for a variety of magnitudes that result. Furthermore, we demonstrate how fault geometry (variable strike and dip) can alter calculated ground‐shaking intensities at specific sites by changing the source‐to‐site distance for ground‐motion prediction equations (GMPEs). Our findings show that improved fault‐based seismic hazard calculations require detailed along‐fault throw‐rate profiles based on well‐constrained local 3D fault geometry for calculating recurrence rates and shaking intensities.

The phase I main canal of the Middle Route of the South-to-North Water Diversion Project crosses the coal mining area in Yuzhou city, and thus it is very important to predict the surface subsidence of the goaf. The GIS-based prediction system for Yuzhou goaf area subsidence has been developed by data collection, and the subsidence, horizontal movement, tilt and curvature are predicted for five mined out areas. The results show that the surface movement and deformation in the strike and dip directions are not more than the stability indexes specified in the coal mining regulation under buildings, water-bodies and railways, indicating that the residual deformation will not cause damage against the canal. The forecasting and monitoring values of Guo coal mine goaf and original Xinfeng goaf, located in Liang Town, Yuzhou City, are relatively large, thus the canal in this region may be affected and the safety monitoring should focus on this region.

Stochastic modeling techniques have been widely applied to oil-gas reservoir lithofacies. Markov chain simulation, however, is still under development, mainly because of the difficulties in reasonably defining conditional probabilities for multi-dimensional Markov chains and determining transition probabilities for horizontal strike and dip directions. The aim of this work is to solve these problems. Firstly, the calculation formulae of conditional probabilities for multi-dimensional Markov chain models are proposed under the full independence and conditional independence assumptions. It is noted that multi-dimensional Markov models based on the conditional independence assumption are reasonable because these models avoid the small-class underestimation problem. Then, the methods for determining transition probabilities are given. The vertical transition probabilities are obtained by computing the transition frequencies from drilling data, while the horizontal transition probabilities are estimated by using well data and the elongation ratios according to Walther’s law. Finally, these models are used to simulate the reservoir lithofacies distribution of Tahe oilfield in China. The results show that the conditional independence method performs better than the full independence counterpart in maintaining the true percentage composition and reproducing lithofacies spatial features.

Topographic shielding (TS) is an important factor in cosmogenic nuclide surface exposure dating. The development of geographic information systems (GIS) and the availability of digital elevation models (DEMs) make it possible to derive this factor directly from a DEM. Most available GIS models derive the TS factors for an area (all cells in a DEM) without the consideration of surface conditions of individual sites, such as the strike, dip, and height above ground, into the calculation. This paper presents a new GIS model to derive the TS factors for discrete sample sites. This model uses the Skyline and Skyline Graph functions in ArcGIS to extract the set of azimuth and elevation angles of topographic obstructions around each site from a DEM (considering the sample height above ground) and then incorporates the strike and dip information of the sample surface to derive the TS factor. All processing tools and steps are streamlined in ArcGIS modelbuilder and this model can be run like a standard ArcGIS geoprocessing tool. It provides an easy and user-friendly means to derive the TS factors for discrete samples based on a DEM and the measured strike, dip and sample height for each site.

The Linnan subsag is a petroliferous, secondary tectonic unit of the Huimin sag that is located in the western part of the Jiyang depression in the Bohai Bay basin, eastern China. In this study, the authors calculated basin extensional rate and slipping displacement of boundary faults in the dip and strike directions, using seismic and drilling data. The evolution of the Linnan transtensional basin from the Eogene through the Quaternary is quantitatively described, and a dynamic model is established. The Linshan and Xiakou boundary faults of the Linnan subsag are used as a case study to describe a method to calculate the strike and dip slipping displacements of active faults under oblique extension. The results quantitatively illustrate the behavior of the Linnan subsag boundary faults over time. The Linnan subsag transtensional basin experienced four stages of evolution: weak extension during the Kongdian Formation, rapid extension and fault depression during the fourth member of the Shahejie Formation, intensive transtension and fault depression during the third member of the Shahejie Formation–Dongying Formation, and weakening fault depression during the Guantao Formation–Pingyuan Formation. The results of this study provide further understanding of the processes of petroleum migration and accumulation in the region. Keywords: Transtensional basin, Fault activity, Quantitative calculation, Basin evolution model, Linnan subsag, Bohai Bay basin

On August 8, 2017, an earthquake of M 7.0 occurred at Jiuzhaigou. Based on the Sentinel-1 satellite InSAR data, we obtained coseismic deformation field and inverted the source slip model. Results show that this event is dominated by strike slip, and the total released seismic moment is 8.06 × 1018 Nm, equivalent to an earthquake of Mw ~ 6.57. We calculated static stress changes along strike and dip direction, and the static stress analysis show that the average stress drop are at low level, which may be responsible for the low level of ground motion during Jiuzhaigou earthquake. The coseismic Coulomb stress changes are calculated base on the inverted slip model, which revealed that 82.59 % of aftershocks are located in the Coulomb stress increasing area, 78.42 % of total aftershocks may be triggered by the mainshock aftershock, indicating that the mainshock has a significant triggering effect on the subsequent aftershocks. Based on stochastic finite fault model, we simulated regional peak ground acceleration (PGA), peak ground velocity (PGV) and the intensity, and results could capture basic features associated with the ground motion patterns. Moreover, the simulated results reflect the obvious rupture directivity effect.

Overcharging in rocks (wall faces) during blasting and excavation usually causes damage to rock mass in most mining and quarry industries. This creates blast-induced fractures which can relates with pre-existing fracture pattern thereby increasing sliding and rockfall from the crest and body of an excavated wall. The spacing and orientation of pre-existing fractures are predominant at a small-scale mining (galamsey) site at ‘Atta ne Atta', a town near Beposo, in the Western Region of Ghana. Geotechnical field studies were carried out to investigate the possibility of any instability within the area to eradicate the occurrence of an unexpected future wall failure (rockfall). The geotechnical mapping conducted was focused on fracture distribution and spacing. Mean spacing (Sm) of existing fractures was calculated and corrections were made to obtain calculated spacing (Sc). The scanlines of wall face 001 and wall face 002 intersect with their corresponding strike and dip at 78° and 80° respectively creating a slightly favourable fracture pattern and rock wall stability. The fracture pattern created at Wall Face 003 and Wall Face 004 were unfavourable for rock stability with their corresponding scanlines having a strike and sip of 67° and 73° respectively. The instability of these wall faces (003 and 004) is as a result of parallel orientation of the induced fractures to the strike of the pre-existing fractures. Observations made from the stereographic projections and rose diagram indicate a cluster of fracture patterns with a general strike of NNE-SSW. Hence, the fracture patterns in the study area are composed of favourable (stable) rock mass at some walls and unfavourable (unstable) rock mass at other wall faces due to overcharging of blast holes.

On 12 June 2017 (UTC 12:28:38.26) a magnitude Mw 6.3 earthquake occurred offshore Lesvos Island in SE Aegean Sea, which was widely felt, caused 1 fatality, and partially ruined the village of Vrisa on the south-eastern coast of the island. I invert broad band and strong motion waveforms from regional stations to obtain the source model and the distribution of slip onto the fault plane. The hypocentre is located at a depth of 7 km in the upper crust. The mainshock ruptured a WNW-ESE striking, SW dipping, normal fault, projecting offshore and bounding the Lesvos Basin. The strongest and most aftershocks clustered away from the hypocentre, at the eastern edge of the activated area. This cluster indicates the activation of a different fault segment, exhibiting sinistral strike-slip motions, along a plane striking WNW-ESE. The slip of the mainshock is confined in a single large asperity, WNW from the hypocentre, with dimensions 20 km × 10 km along fault strike and dip, respectively. The average slip of the asperity is ~ 50 cm and the peak slip is ~ 1 m. The rupture propagated unilaterally towards WNW to the coastline of Lesvos island at a relatively high speed (~ 3.1 km/s). The imaged slip model and forward modelling was used to calculate peak ground velocities (PGVs) in the near-field. The damage pattern produced by this earthquake, especially in the village of Vrisa is compatible with the combined effect of rupture directivity, proximity to the slip patch and the fault edge, spectral content of motions, and local site conditions.

Multichannel seismic reflection profiles show that the Outer Cilicia Basin evolved mainly during the uppermost Messinian–Quaternary as an asymmetric piggyback basin on the hanging wall of the large south-verging Kyrenia thrust culmination, following the partitioning of the much larger Miocene basin. A major north-verging backthrust and several similarly-verging smaller splays developed during the deposition of the uppermost Messinian–Quaternary succession, elevating the southern sector of the Outer Cilicia Basin ~250–500 ms above the central portion of the basin. An E–W trending zone characterized by 6–9 positive flower structures which are cored by the Messinian evaporite successions developed immediately north of the backthrust. Two prominent broadly E–W striking extensional fault zones define the tectonic framework of the north and south margins of the basin: (a) the Zafer–Kormakiti zone in the south with 5–6 internally parallel and invariably north-dipping large listric extensional faults developed immediately north of the Kyrenia Range and (b) the Anamur–Silifke zone in the north with 4–8 internally parallel and steeply north- and south-dipping planar faults defining a series of shore-parallel horst and graben structures developed immediately south of the Central Taurus Mountains. The Zafer–Kormakiti and the Anamur–Silifke fault zones are shown to be the westward extensions of the uppermost Messinian–Quaternary Misis–Kyrenia and Kozan fault zones, respectively. The tectonic framework of the Miocene successions across the Mut Basin delineated using >310 strike and dip measurements extracted from 1:25,000–1:100,000 maps supplemented by >1200 strike and dip determinations using the rule of Vs and construction of structure contours. These data revealed two distinct regional folds, where the anticlinal and synclinal axes are oriented WNW–ESE and NE–SW directions. Geological cross sections constructed suggest that the folds are likely cored by broadly southerly verging deep-seated blind thrusts.

Interferometric synthetic aperture radar (InSAR) technology can obtain one-dimensional surface displacements in the radar line of sight (LOS). In the field of mining subsidence, large 3D movements often occur at the same time, and hence InSAR derived one-dimensional LOS displacements can hardly reflect the actual surface motion in mining areas. To realize the monitoring of three-dimensional large surface displacements in mining areas, a method for monitoring three-dimensional large surface displacements in mining areas that combines SAR pixel offset tracking (OT) and an improved mining subsidence model is proposed in this article. First, a new functional relationship between surface subsidence and horizontal movement combined with the characteristics of the overburden rock stress and the deformation characteristics of the fractured rock mass in coal mining areas is established. Then, a three-dimensional surface deformation model is established based on the proposed relationship between surface subsidence and horizontal movement and the radar projection equation, and finally, the optimal parameters of the deformation model are inverted iteratively using LOS deformation results obtained by OT method to retrieve the three-dimensional large displacements of the surface. The significant advantage of the method proposed in this article is that it can accurately acquire the 3D large surface displacements using only two SAR amplitude images with the same imaging geometry. To verify the accuracy and reliability of the proposed algorithm, two scenes of high-resolution spotlight TerraSAR-X images are used in this paper to conduct a three-dimensional surface displacement monitoring experiment on a working panel in the Daliuta mining area in Shaanxi Province, China, based on the proposed method. Experimental monitoring results show that the maximum surface subsidence is approximately 4.5 m, and the maximum horizontal movements in the strike and dip directions are approximately 1.4 m and 1.2 m, respectively. Using GPS measurements to verify the monitoring results, the root mean square error (RMSE) of vertical subsidence is 6.8 cm, and the RMSE of horizontal movement is 7.1 cm. Compared with those in the original mining subsidence model, the accuracies of vertical subsidence and horizontal movement in the proposed model are increased by 28.2% and 37.5%, respectively, which proves the reliability and accuracy of the proposed method.

Various observations are made to invert for the source model of the 2015 Gorkha earthquake. Previously published slip models involve different slip distributions and slip amplitudes. To obtain a robust model, we jointly invert for the rupture process of the Gorkha earthquake using three types of observations: Global Positioning System (GPS), Interferometric Synthetic Aperture Radar (InSAR), and teleseismic P wave data. Three constraints (i.e., spatial and temporal smoothness and minimum moment constraints) are applied to regulate the rupture process. The weight ratios between data sets and prior constraints are determined from a new developed generalized Akaike’s Bayesian Information Criterion (gABIC) weight determination method. This gABIC method can simultaneously and objectively weigh various kinds of observations and prior constraints, rather than being limited to the two types in the traditional ABIC method. The inverted slip model reveals the seismic moment of the earthquake is 9.40 × 1020 N m released primarily in the first 60 s, equivalent to Mw 7.92. The rupture front propagates unilaterally along the strike direction and spreads in both the strike and dip directions. The slip distribution shows one large slip patch with two peaks along the strike direction with a maximum slip amplitude of approximately 7.6 m and identifies large slips (> 2 m) that occur in the updip section of the Main Himalayan Thrust (MHT) fault plane. Our results indicate that the released slip amplitude is larger than the accumulated slip amplitude since 1833, so the 2015 earthquake likely does not overlap with the 1833 earthquake.

Interpretation of 2-D deep seismic reflection data can be limited by the recording of out-of-plane reflections that cannot be readily distinguished from those originating beneath a seismic line. Here I present a method analogous to semblance velocity analysis that utilizes varying source-receiver azimuths to derive continuous estimates of 3-D reflector orientations along onshore 2-D reflection profiles. For each zero-offset time within a common depth point supergather, the semblance is calculated along 3-D travel time curves, and the dip and strike of the most coherent reflection is determined. Relative errors in these angles are derived from the range of travel time curves that have semblance values greater than a specified fraction, for example 90%, of the maximum. The method is illustrated using a section from line 10GA-YU1 from the Youanmi terrane of the Yilgarn craton in Australia in which the original field data have been replaced with synthetic in-line and cross-line reflections. Reflector orientations are generally well recovered where the range of available source-receiver azimuths is greater than 20o, but the method fails at lower ranges where the seismic line is almost linear, and this behavior is also observed in analysis of the field data. Nevertheless when using a realistic 1-D velocity function the orientation of upper crustal shear zones can be readily determined, and on unmigrated sections subhorizontal sills can be distinguished on the basis of their geometry from the mid-crustal reflectivity. In future surveys, reflector orientations can be determined along the near-linear sections of a seismic profile by deploying additional receivers, perhaps as cross-line recording spreads, to supplement the limited range of azimuths available from the in-line acquisition. The method can in principle be extended to marine reflection surveys, and more complex sub-surface velocity models.

Detection and analysis of linear features related to surface and subsurface structures have been deemed necessary in natural resource exploration and earth surface instability assessment. Subjectivity in choosing control parameters required in conventional methods of lineament detection may cause unreliable results. To reduce this ambiguity, we developed LINDA (LINeament Detection and Analysis), an integrated tool with graphical user interface in Visual Basic. This tool automates processes of detection and analysis of linear features from grid data of topography (digital elevation model; DEM), gravity and magnetic surfaces, as well as data from remote sensing imagery. A simple interface with five display windows forms a user-friendly interactive environment. The interface facilitates grid data shading, detection and grouping of segments, lineament analyses for calculating strike and dip and estimating fault type, and interactive viewing of lineament geometry. Density maps of the center and intersection points of linear features (segments and lineaments) are also included. A systematic analysis of test DEMs and Landsat 7 ETM+ imagery datasets in the North and South Eastern Deserts of Egypt is implemented to demonstrate the capability of LINDA and correct use of its functions. Linear features from the DEM are superior to those from the imagery in terms of frequency, but both linear features agree with location and direction of V-shaped valleys and dykes and reference fault data. Through the case studies, LINDA applicability is demonstrated to highlight dominant structural trends, which can aid understanding of geodynamic frameworks in any region.

Seismic fault detection using principal component analysis (PCA) is an effective method for interpreting fault distribution and orientations in the Bakken Formation. The PCA fault attribute indicates significantly different, and geologically more plausible, 3D fault distributions than conventional seismic attributes, such as curvature. The PCA fault attribute has identified different fault patterns in the Upper, Middle, and Lower Bakken members and the Three Forks Formation. Two distinct fault trends in approximately 40°–50° northeast–southwest and 50°–60° northwest–southeast directions are observed in the Bakken Formation in the study area, and they are apparent on the strike and dip attributes derived from the PCA fault attribute. Fault cuts interpreted from missing well-log sections correlate well with the PCA fault attribute. Seismically derived fault orientations correlate with borehole image log data in the horizontal wells. Crossing conjugate faults observed on the fault dip attribute may result in the widening of the faulted area and localized thinning of the rock sequence where the faults intersect, and this could potentially enhance permeability along the fault strike.

Tectonic tremor and low-frequency earthquakes (LFEs) are relatively poorly studied in the Alaska-Aleutian subduction zone due to the limited data availability, difficult logistics, and rugged terrain. Using 2months of continuous data recorded by a mini seismic array in the Akutan Island, we detect near-continuous tremor activity with an average of 1.3h of tectonic tremor per day using a beam backprojection method. Tremor sources are clustered in two patches with an ~25km gap in between them. In addition, we visually identify three low-frequency earthquakes, and using them as templates, we detect ~1300 additional LFEs applying a matched-filter method. Tremor and LFE activities agree well in space and time, and LFEs show a much smaller recurrence interval during tremor than during non-tremor time periods. Tremor sources propagate both along the strike and dip directions of the subduction fault with velocities ranging between 13 and 110km/h. Prolific patchy tremor and LFE activities suggest lateral heterogeneity in the locked to freely slipping transition zone, indicating that slow earthquakes may play an important role in the earthquake cycles in this subduction zone.

Water flooding disasters are one of the five natural coal-mining disasters that threaten the lives of coal miners. The main causes of this flooding are water-conducting fractured zones within coal seams. However, when resistivity methods are used to detect water-conducting fractured zones in coal seams, incorrect conclusions can be drawn because of electrical anisotropy within the water-conducting fractured zones. We present, in this paper, a new geo–electrical model based on the geology of water-conducting fractured zones in coal seams. Factors that influence electrical anisotropy were analyzed, including formation water resistivity, porosity, fracture density, and fracture surface roughness, pressure, and dip angle. Numerical simulation was used to evaluate the proposed electrical method. The results demonstrate a closed relationship between the shape of apparent resistivity and the strike and dip of a fracture. Hence, the findings of this paper provide a practical resistivity method for coal-mining production.

This paper describes a simple methodology for determining paleocurrent directions or fracture orientations from core that has traditionally been considered unoriented. Provided the core does not intersect bedding at a 90° angle, and that the attitude of bedding (strike and dip) and the drill hole (azimuth and inclination) are known, paleocurrent directions and fracture orientations can be determined in present-day geographic coordinates without the need for scribed core. This technique supplements dip-meter and borehole-image logs and allows the use of structures that are too small to be imaged geophysically.

We introduce a new algorithm for determining the geometry of active parts of faults. This algorithm uses surface measurements of displacement fields and local modeling of the Earth’s crust as a half-space elastic medium. The numerical method relies on iterations alternating non-linear steps for recovering the geometry and linear steps for reconstructing slip fields. Our algorithm greatly improves upon past attempts at reconstructing fault profiles. We argue that these past attempts suffered from either the restrictive assumption that the geometry of faults can be derived using only uniformly constant slips or that they relied on arbitrary assumptions on the statistics of the reconstruction error. We test this algorithm on the 2006 Guerrero, Mexico, slow slip event (SSE) and on the 2009 SSE for the same region. These events occurred on a relatively well-known subduction zone, whose geometry was derived from seismicity and gravimetric techniques, see Kostoglodov et al. (Geophys Res Lett 23(23):3385–3388, 1996), Pardo and Suarez (J Geophys Res 100(B7):357–373, 1995), Singh and Pardo (Geophys Res Lett 20(14):1483–1486, 1993), so our results can be compared to known benchmarks. Our derived geometry is found to be consistent with these benchmarks regarding dip and strike angles and the positioning of the North American Trench. In addition, our derived slip distribution is also consistent with previous studies (all done with an assumed fixed geometry), see Larson et al. (Geophys Res Lett 34(13), 2007), Bekaert et al. (J Geophys Res: Solid Earth 120(2):1357–1375, 2015), Radiguet et al. (Geophys J Int 184(2):816–828, 2011, J Geophys Res 2012), Rivet et al. (Geophys Res Lett 38(8), 2011), Vergnolle et al. (J Geophys Res: Solid Earth 115(B8), 2010), Walpersdorf et al. Geophys Res Lett 38(15), 2011), to name a few. We believe that the new computational inverse method introduced in this paper holds great promise for applications to blind inversion cases, where both geometry and slip distribution are unknown.