Geological 3D Research Articles

Geometry of the Bushveld Complex from 3D potential field modelling

A full three-dimensional (3D) potential field model of the central and southern Bushveld Complex reveals information about the Complex in areas obscured by younger geological cover. Previously, two-dimensional gravity models and a few magnetic models limited to certain sections of the Bushveld Complex have been used to propose geometries for the Rustenburg Layered Suite, especially in the western and eastern lobes. These models were often used to support different emplacement models. Although these models provided valuable information, two-and-a-half-dimensional (2.5D) potential field modelling is not well suited to modelling complex 3D geology. Also, in most cases, only the magnetic or gravity data were modelled, but jointly modelling both data sets better constrains the results, as was shown recently for a 3D model of the northern lobe. Joint 3D modelling of regional gravity and magnetic data combined with published crustal thickness models derived from broadband seismic tomography studies and constrained by density and susceptibility data, geologic mapping, boreholes and seismic reflection data were used to create a 3D model of the central and southeastern sections of the Bushveld Complex, as well as the southern part of the northern lobe. The model shows a complex geometry with thick continuous Rustenburg Layered Suite S in most of the western and southeastern lobes, but less continuous Rustenburg Layered Suite in the eastern lobe. Large domes or thick granites and granophyre in the latter interrupt the continuity of the Rustenburg Layered Suite and the western and eastern lobes are strictly speaking only partially connected in places. However, they are not separate intrusions, but one disconnected by pre-existing and synmagmatic updoming. Three possible feeders were modelled in the northern, western, and south-eastern lobes.

Stratigraphical and sedimentological relationships of the Bolognano Formation (Oligocene–Miocene, Majella Mountain, Central Apennines, Italy) revealed by geological mapping and 3D visualizations

Stratigraphical and sedimentological relationships of the Bolognano Formation (Oligocene–Miocene, Majella Mountain, Central Apennines, Italy) revealed by geological mapping and 3D visualizations

A Geology and Geodesy Based Model of Dynamic Earthquake Rupture on the Rodgers Creek‐Hayward‐Calaveras Fault System, California

AbstractThe Hayward fault in California's San Francisco Bay area produces large earthquakes, with the last occurring in 1868. We examine how physics‐based dynamic rupture modeling can be used to numerically simulate large earthquakes on not only the Hayward fault, but also its connected companions to the north and south, the Rodgers Creek and Calaveras faults. Equipped with a wealth of images of this fault system, including those of its 3D geology and 3D geometry, in addition to inferences about its interseismic creep‐rate pattern and rock‐friction behavior, we use a finite‐element computer code to perform 3D dynamic earthquake rupture simulations. We find that the rock properties affect the locations and amount of slip produced in our simulated large earthquakes. Crucial factors that control rupture behavior in our modeling are the earthquake nucleation locations, the fault geometry, and the data that reveal where the fault system is creeping or locked. Our findings suggest that large Rodgers Creek‐Hayward‐Calaveras‐Northern Calaveras (RC‐H‐C‐NC) fault‐system earthquakes may result from dynamic rupture that starts in a locked part of the fault system, but is then stopped by the creeping parts, leading to high‐magnitude‐6 earthquakes; or, from dynamic rupture that starts in a locked part of the fault system, then cascades through some of the creeping parts, leading to magnitude‐7 earthquakes.

Regional groundwater flow and karst evolution\u2013theoretical approach and example from Switzerland

In regional scale aquifers in the Rhine Valley and Tabular Jura east of Basel (Switzerland), the groundwater circulation was investigated using regional-scale geological and hydraulic 3D models. The main aquifers in the area comprise the Quaternary aquifer of unconsolidated gravel deposits along the River Rhine and its tributaries, as well as the regional scale karst aquifer within the Upper Muschelkalk. Land subsidence, a process likely associated with salt solution mining, indicates further subordinate groundwater bearing segments and complex groundwater interactions along fault zones. In the aquifer systems we investigated, regional-scale groundwater circulation was simulated and visualized in relation to the geological settings. Lithostratigraphic units and fault structures were parameterized and analyzed, including the sensitivity of hydraulic properties and boundaries. Scenario calculations were used to investigate the sensitivity that the aquifer systems had to hydraulic parameter changes during Quaternary aggradation and degradation in the main valley. Those calculations were also done for base-level changes in the Rivers Rhine and Birs. For this purpose, this study considered probable historic base-levels before river regulation occurred, and before river dams and power plants were constructed. We also focused on scenarios considering increased groundwater recharge rates, e.g. due to exceptional long-lasting precipitation, or heavy rainfall events in the catchment area. Our results indicate that increased groundwater recharge rates in the catchment areas during such events (or periods) are associated with orders of magnitude increases of regional inflow into the Upper Muschelkalk karst aquifer. Furthermore, the groundwater fluctuations and groundwater saturated regions within the karst aquifer shift to places where high densities of sinkholes are documented. When the surface water base-levels adapt to probable historic levels, it leads to increased hydraulic gradients (i.e. local lowering of the groundwater level by up to 7 m). Those increased gradients are associated with increased groundwater flow within some aquifer regions that are particularly prone to karst development.

3D Geological Model of the Touro Cu Deposit, A World-Class Mafic-Siliciclastic VMS Deposit in the NW of the Iberian Peninsula

The Touro volcanogenic massive sulfide (VMS) deposit is located in the NW of the Iberian Variscan massif in the Galicia-Trás-os-Montes Zone, an amalgamation of several allochthonous terrains. The Órdenes complex is the most extensive of the allochthone complexes, and amphibolites and paragneisses host the deposit, characterized as being massive or semimassive (stringers) sulfides, mostly made up of pyrrhotite and chalcopyrite. The total resources are 103 Mt, containing 0.41% copper. A 3D model of the different orebodies and host rocks was generated using data from 1090 drill core logs. The model revealed that the structure of the area is a N–S-trending antiform. The orebodies crop out in the limbs and in the hinge zone. The mineralized structures are mostly tabular, up to 100 m in thickness and subhorizontal. Based on the petrography, geochemistry and the 3D model, the Touro deposit is classified as a VMS of the mafic-siliciclastic type formed in an Ordovician back-arc setting, which was buried and metamorphosed in Middle Devonian.

Crane Lifting Optimization and Construction Monitoring in Steel Bridge Construction Project Based on BIM and UAV

Modular construction methods are adopted in many spatial and temporal limited projects. As the major equipment used in modular construction, the mobile crane affects the safety and efficiency of construction significantly. Currently, building information modeling (BIM) is widely adopted to improve the lifting operation planning of cranes. However, the inaccurate simulation of the dynamic construction environment makes those BIM‐based lifting operation planning methods unsuitable for land mobile cranes operation planning, such as in the overpass bridge construction project, which may cause several safety risks during the lifting process. Based on an overpass steel bridge construction project, this paper attempted to integrate the BIM and unmanned aerial vehicles (UAVs) to streamline lifting operation planning and construction monitoring. Specifically, in the preliminary stage, a level of development (LOD) 400 steel superstructure model was built and then divided into eighty sections. In addition, a three‐dimensional (3D) geology model of the as‐is construction site was modeled by UAV‐captured images. Then, a fusion model which contains the lifting modules models, the as‐is site model, and the crane model was gathered, based on which the collision detection was conducted by 4D crane operating path simulation. According to the results, three potential collisions were found and eliminated by lengthening the jib of the crane from 43.5 m to 46.5 m. Furthermore, the optimum crane location for lifting each steel structure was determined based on the 3D geology model. The study shows that the UAV is able to acquire geological information and then 3D simulates the real construction environment quickly and accurately. Furthermore, BIM and UAV have the potential to optimize the design and construction as well as the monitoring of bridge projects.

基于形状上下文的成矿构造形态控矿特征深度学习及三维成矿预测——以大尹格庄金矿床为例

基于形状上下文的成矿构造形态控矿特征深度学习及三维成矿预测——以大尹格庄金矿床为例

A 3D Geological Model Constrained by Gravity and Magnetic Inversion and its Exploration Implications for the World‐class Zhuxi Tungsten Deposit, South China

AbstractThe Zhuxi tungsten deposit in Jiangxi Province, South China, contains a total W reserve of about 2.86 Mt at an average grade of 0.54 wt% WO3, representing the largest W deposit in the world. Numerous studies on the metallogeny of the deposit have included its timing, the ore‐controlling structures and sedimentary host rocks and their implications for mineral exploration. However, the deep nappe structural style of Taqian–Fuchun metallogenic belt that hosts the W deposit, and the spatial shape and scale of deeply concealed intrusions and their sedimentary host rocks are still poorly defined, which seriously restricts the discovery of new deposits at depth and in surrounding areas of the W deposit. Modern 3D geological modeling is an important tool for the exploration of concealed orebodies, especially in brownfield environments. There are obvious density contrast and weak magnetic contrast in the ore‐controlling strata and granite at the periphery of the deposit, which lays a physical foundation for solving the 3D spatial problems of the ore‐controlling geological body in the deep part of the study area through gravity and magnetic modeling. Gravity data (1:50000) and aeromagnetic data (1:50000) from the latest geophysical surveys of 2016–2018 have been used, firstly, to carry out a potential field separation to obtain residual anomalies for gravity and magnetic interactive inversion. Then, on the basis of the analysis of the relationship between physical properties and lithology, under the constraints of surface geology and borehole data, human–computer interactive gravity and magnetic inversion for 18 cross‐sections were completed. Finally, the 3D geological model of the Zhuxi tungsten deposit and its periphery have been established through these 18 sections, and the spatial shape of the intrusions and strata with a depth of 5 km underground were obtained, initially realizing “transparency” for ore‐controlling bodies. According the analysis of the geophysical, geochemical, and geological characteristics of the Zhuxi tungsten deposit, we discern three principles for prospecting and prediction in the research area, and propose five new exploration targets in its periphery.

Constructing 3D Geological Model for Tertiary Reservoir in Khabaz Oil Field by using Petrel software.

3D Geological model for tertiary reservoir in khabaz oil field had been constructed byusing petrel software. Seven wells have been selected in this study in order to designPetrophysical properties (porosity, water saturation, and permeability). Structural modelcan be clarified tertiary reservoir in term of geological structures is a symmetrical smallanticline fold with four faults. Tertiary reservoir consist of six units are (Jeribe, UnitA,UnitA', UnitB, UnitBE, and UnitE). According to Petrophysical properties, layering hadbeen constructed for each tertiary units. Petrophysical model has been designed using thesequential Gaussian simulation algorithm as a geostatistical method. The results illustratesthat Unit B and Unit BE have the best petrophysical properties and the big amount of oil.

Modeling Geoelectric Fields Induced by Geomagnetic Disturbances in 3D Subsurface Geology, an Example From Southeastern Australia

AbstractGeomagnetic storms can cause power grid instabilities and blackouts due to excessive geomagnetically induced currents (GICs) flowing in electric transmission systems. In this study, we assess regional vulnerability to GICs by modeling the geoelectric fields induced by significant historic geomagnetic disturbance events in the presence of 3D subsurface geology using data from the Australian Lithospheric Architecture Magnetotelluric Project (AusLAMP) magnetotelluric array, Australia‐Wide Array of Geomagnetic Stations (AWAGS) magnetometer array, and Geoscience Australia geomagnetic observatory network. We analyze the vertical component of the magnetic field with respect to the horizontal magnetic‐field polarization for two magnetic storms and gain insight into the inductive effects associated with field polarization orientations in the 3D case. We also analyze the telluric field intensity and polarization for a unit geomagnetic field polarized in northerly and easterly directions at AusLAMP sites and find that in the presence of 3D geology the induced field has a very polarization‐sensitive anomaly. We model the geoelectric fields in southeastern Australia for the 1989 “Québec storm.” The induced ground electric fields are typically in the range 1,000–2,000 mV/km with a few sites within 2,000–5,000 mV/km on highly resistive regions and in coastal areas, and below 300 mV/km on inland sedimentary basins. The current study focuses on magnetic‐field variations with periods between 120 and ~20,000 s due to bandwidth limits in our magnetotelluric tensor data and the Nyquist limit for the 60 s sampling of our geomagnetic‐field data. Hence, our modeled maximum values should be considered lower estimates of potential real values.

A new multi-disciplinary integrated steering technology for horizontal wells in tight sandstone gas reservoirs: A case study of the Ordos Basin

The sandstone layers of the Upper Paleozoic tight clastic gas reservoirs in the Ordos Basin are generally distributed in a pattern of nearly NS strip, and the channel branches and intersects frequently. A single sand body is in a multilayered contact mode resulted from lateral accretion, and the sand bodies at the river intersections present a feature of lying in the nearly EW direction, which brings great difficulties to the geo-steering of horizontal wells. In order to improve the reservoir drilling rate of horizontal wells, this paper systematically analyzed the geo-steering status of horizontal wells and the sedimentary characteristics of reservoirs. Then, the spatial distribution of reservoirs was predicted using 3D geological modeling and 3D seismic. In addition, based on the cognitions on the space distribution of sand bodies from the drilled horizontal wells, the horizontal well geo-steering technology and method were constantly improved and enriched. Thus, an integrated steering technology of “fine sublayer correlation for target entering, geology in small scale, and seismic in large scale” based on in-depth integration of multidisciplinary thinking was newly formed, and it was also applied on site. And the following research results were obtained. First, under the guidance of the sedimentation model, the target entering process is controlled precisely and the success rate of one-trip target entering is improved, so it is one important method for the target steering of deviated hole sections. Second, geological modeling can guide the drilling of horizontal wells, but to some extent, it is deviated from the real underground geologic bodies, so it can be used as an auxiliary horizontal-well steering method. Third, 3D seismic steering can tell the boundary of complex river channel and discriminate the spatial relative location of predominant sand bodies, so it is the primary method for horizontal-well steering to provide excellent judgment and guidance on the steering of horizontal hole sections. Fourth, owing to the application of this new method in 62 horizontal wells drilled in the tight gas demonstration area, the average horizontal section length reaches 1430 m, the average sandstone drilling rate is 86.2%, the average gas layer drilling rate is 70.2%, and the gas layer drilling rate of horizontal wells is increased by more than 10%.

A 3D Geological Model as a Base for the Development of a Conceptual Groundwater Scheme in the Area of the Colosseum (Rome, Italy)

Geological models are very useful tools for developing conceptual schemes owing to their capacity to optimize the management of stratigraphic information. This is particularly true in areas where archaeological heritage is exposed to hydrogeological hazards; 3D models can constitute the first step toward the construction of numerical models created to understand processes and plan mitigation actions to improve visitor safety and preserve archaeological heritage. This paper illustrates the results of a 3D hydrostratigraphic model of the site of the Colosseum in the Central Archaeological Area of Rome. In recent years, this area has experienced numerous floods caused by intense meteorological events. A new borehole survey provided the opportunity to update previous maps and cross sections and build a local scale 3D model. The resulting conceptual model was used to identify primary gaps in existing knowledge about the groundwater system and to optimize the planning of a piezometer monitoring network. Further studies can then focus on the development of groundwater numerical models to verify hypotheses regarding inflow-outflow dynamics and facilitate the optimization of water management.

Urban Geological 3D Modeling Based on Papery Borehole Log

Borehole log is important data for urban geological 3D modeling. Most of the current borehole logs are stored in a papery form. The construction of a smart city puts forward requirements for the automatic and intelligent 3D modeling of urban geology. However, it is difficult to extract the information from the papery borehole log quickly. What is more, it is unreliable to rely entirely on automated algorithms for modeling without artificial participation, but there is no effective way to integrate geological knowledge into 3D geological modeling currently. Therefore, it is necessary to research how to use existing papery borehole logs efficiently. To overcome the above obstacles, we designed a method that combines structural analysis and layout understanding to extract information from the borehole log. Then, the knowledge-driven three-dimensional geological modeling is proposed based on dynamic profiles. With these methods, the papery borehole log can be converted into structured data which can be used for data analysis directly, and geological knowledge can be integrated into the process of 3D geological modeling. The 3D geological modeling of Xinyang City based on a papery borehole log has been taken as an example to verify the feasibility of the method.

Variations in the bathymetry and bottom morphology of the Izu-Bonin Trench modelled by GMT

Abstract Cartographic visualisation is a central concept in geoinformatics, and Generic Mapping Tools (GMT) functionality provides a variety of modules for effective mapping. However, due to its specific scripting approach, there is not enough reported experience of GMT mapping, comparing to traditional GIS. This contribution introduces steps that can be taken to perform cartographic mapping and modelling using GMT. Geographically, this paper investigates the Izu-Bonin Trench in the Pacific Ocean. The aim was to compare its geomorphology in two segments, and each was modelled by a series of profiles. The comparative analysis shows that the southern segment is deeper and is a more precisely V-shaped form with a steeper gradient slope. The northern part has an asymmetric slope with submarine terraces to the west and a straight shape to the east. The northern profile is based on 407 samples (13.5%) at depths of −5,600 to −5,800 m, followed by 304 samples at −5,800 to −6,000 m (10%). The southern histogram has a bimodal distribution with two peaks: 523 samples (20%) with depths of −5,800 to −6,000 m. The second peak (10%) is on the Bonin Ridge. The GMT proved to be an effective instrument for marine geological mapping, 3D and 2D modelling, statistical analysis and graphical plotting.

Multi-sensor core logging (MSCL) and X-ray computed tomography imaging of borehole core to aid 3D geological modelling of poorly exposed unconsolidated superficial sediments underlying complex industrial sites: An example from Sellafield nuclear site, UK

The 3D characterisation of geology underlying complex industrial sites such as nuclear plants is problematic due to the presence of the built infrastructure that restricts or in some cases completely prevents access for geologists to the subsurface environment. Outcrops are rare, geophysics surveys are often impossible (particularly at nuclear plants where activities such as vibroseis are frowned upon due to their effect on the infrastructure itself), and boreholes are often the only way to obtain subsurface data. Yet, with sedimentary deposits in particular, geotechnical logging undertaken to specific standards sometimes misses key information that could have been used to directly inform the creation of geological 3D models.Multi-sensor core logging (MSCL) and X-ray computed tomography (XCT) undertaken on core obtained from a borehole within the Sellafield nuclear plant, is used to illustrate the potential for the techniques to contribute significantly to the creation of 3D subsurface geological models, particularly where access is restricted, such as within nuclear industry locations. Geophysical characteristics are recorded and used to reassess and enhance geotechnical descriptions, leading to the modification of existing unit boundaries or the creation of new ones. A new sedimentary log was created and this was used in a comparison with existing logs and nearby historic exposures, and as the basis for an illustration of industrial site to regional correlation.

When seeing what's wrong makes you right: The effect of erroneous examples on 3D diagram learning

SummaryComprehending 3D diagrams is critical for success in scientific practice and research demonstrates that understanding of 3D geology diagrams can be improved by making predictive sketches. In mathematics, explaining erroneous examples can support learning. This study combined these approaches to better understand how to effectively support 3D geologic diagram understanding. Participants generated sketches, explained erroneous example sketches, or copied and explained correct sketches. It was hypothesized that generating sketches or explaining erroneous cases would improve understanding, but an open question was whether these conditions would differ from each other. Explaining erroneous examples and sketching improved understanding whereas explaining correct sketches did not. Further, explaining erroneous examples was a more efficient strategy than sketching. These results indicate that erroneous examples can be effective for supporting 3D diagram comprehension and may be a practical substitute for some traditional sketching activities in the context of real classrooms where class time is limited.

Structural interpretation of SW part of Denizli, Turkey, based on gravity data analysis

Detection of the linear features is a useful task to understand the tectonism of a region. Gravity anomaly data was used to investigate the tectonic structures of SE part of Denizli, western Anatolia. This region is a tectonically active transition zone between Aegean extensional and Anatolian Taurides compressional provinces. Lineaments are appearance of the instantaneous change in the density of the subsurface rocks in gravity data. To determine the lineaments, derivative-based edge detection methods, horizontal gradient, analytic signal, tilt angle and hyperbolic tilt angle applied gravity anomaly data. In defining the lineaments, 3D sediment-basement model, elevation, geology and seismicity data were used comparatively. The sediment-basement topography was modelled by 3D inversion of gravity data. The maximum sediment thickness is defined 2.4 km in the northern part of Acipayam basin and 2.3 km in the southern part of Denizli basin. The earthquake distribution map, geology and elevation maps were provided insight the linear features of the region. As a result of the study, the new tectonic map is attained. Besides the known structures, many new lineaments and some buried faults were defined in the study area.

GMT Based Comparative Geomorphological Analysis of the Vityaz and Vanuatu Trenches, Fiji Basin

The study is geographically focused on the two deep-sea trenches: Vanuatu and Vityaz, Fiji Basin, East Australia, located in the area of the double convergent complex boundary of Pacific and Indo-Australian plates in the North Fiji back-arc basin. Complex geophysical settings results in the formation of the trenches, seismicity, geodynamic complexity and instability of the region. The work aimed at modelling and comparative statistical analysis of the bathymetry and geomorphology of two trenches. Technically, the methodology of this work is based on the Generic Mapping Tools (GMT) using cartographic mapping of the geophysical, tectonic and geological settings, 2D and 3D modelling, visualizing raster grids GEBCO, ETOPO1, ETOPO5. Histogram topographic equalization (equalized, normalized, quadratic) was done using module ’grdhisteq’. Modelling geoid and gravity was based on EGM96 by sequence of GMT modules. The cross-spectrals of 2D binary raster grids were compared and their coherency plotted by ’grdfft’. The automated cross-sectioning was done using ’grdtrack’ module. The results include modelled transects visualizing trenches asymmetry, bathymetric and geomorphic variations. Vityaz Trench is shallower with depths <–6,100 m, has ’bell-shape’ data distribution with two peaks at ranges –3,500 m to –3,700 m, and –4,800 m to –5,000 m. Vanuatu Trench reaches up to –7,000 m with majority of values between –5,000 m to –3,000 m, even data distribution with depth increasing at –2,200 m to –800 m. Geomorphic form of both trenches varies: Vityaz has flat wide bottom similar to a trough, steeper gradient eastern slope. Vanuatu has V-form classic shape with gentle shapes on both slopes. Selected segment of Vityaz has shallower depths with maximal <–5,000 m while Vanuatu is deeper (–6,000 m). Cartographic functionality of the GMT is presented by various cartographic projections: Mercator, Behrman, Cylindrical Stereographic, Hammer retroazimuthal. 3D modelling was done using GMT module ’grdview’. Trenches were visualized and rotated at 160°/45°azimuth. Presented maps, 2D and 3D models and graphics are plotted and visualized by GMT with selected code snippets explained. Current work contributes to the methods of the modelling of deep-sea trenches geomorphology.

A geophysical and geomorphological investigation of large-offset normal faulting in Beachlands, Auckland

ABSTRACT The identification and characterisation of faults in urban environments is important to inform seismic and landslide hazard, yet urban development often obscures geological and geomorphological evidence of fault traces. On the other hand, urban development also generates a wealth of borehole data, which, when combined with geophysical surveys, can enable a view into the subsurface. Here we combine geomorphological and geological mapping, gravity surveying, and 3D geological modelling to identify, map and characterise several faults in Beachlands, Auckland, some of which have large offsets. Our work has identified one new fault, the Motukaraka Fault, and confirmed the presence of two proposed faults, the Waikopua North and Te Puru faults. The Motukaraka and Waikopua North faults are both steeply dipping normal faults, which strike NNW and downthrow Mesozoic basement to the west. The Motukaraka Fault has an offset of 250 m (±100 m) and the Waikopua North Fault a combined offset of 240 m (±50 m) across two parallel fault segments. The Te Puru fault strikes northeast near the northern extent of the Waikopua Fault, and downthrows Mesozoic basement to the northwest by 60–100 m. Further investigations are required to determine whether these buried faults are active.

An integrated geological, geotechnical and geophysical approach to identify predisposing factors for flowslide occurrence

This study combines geological, geotechnical and geophysical analyses to construct a 3D model of the subsoil, based on a significant amount of data collected at a test site in the Lattari mountain range in southern Italy. Several investigation techniques were applied to study the spatial variability of the local stratigraphic setting and relevant geophysical and geotechnical parameters at the slope scale. By integrating field and laboratory measurements, such as geological logs, soil sampling, 2D and 3D electrical resistivity tomography surveys, time domain reflectometry profiles and characteristic curves of electrical resistivity vs saturation degree, the continuous stratigraphy of the pyroclastic cover in question was reconstructed and 3D models of effective saturation degree in different pyroclastic horizons were retrieved. As the proposed procedure is applied to study flowslide initiation, the test site was implemented on a 32° slope affected by historical flowslides. The following factors predisposing to flowslides were identified: steep stratigraphic contact between shallower soils and bedrock, impermeable layers that buffer the draining of the fractured limestone, preferential rainwater infiltration paths, and spatial distribution of water content in the soil.