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Geosciences, Volume 9, Issue 12 (December 2019)

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Open AccessArticle
A Silicified Carboniferous Lycopsid Forest in the Colorado Rocky Mountains, USA
Geosciences 2019, 9(12), 510; https://doi.org/10.3390/geosciences9120510 (registering DOI) - 07 Dec 2019
Abstract
The1930 discovery of Carboniferous lycopsid fossils in south central Colorado resulted in the naming of a new species of scale tree, Lepidodendron johnsonii (=Lepidopholios johnsonii (Arnold) DiMichelle). Cellular structuresof L. johnsonii axes and periderm are preserved in silica—an unusual mode of fossil preservation [...] Read more.
The1930 discovery of Carboniferous lycopsid fossils in south central Colorado resulted in the naming of a new species of scale tree, Lepidodendron johnsonii (=Lepidopholios johnsonii (Arnold) DiMichelle). Cellular structuresof L. johnsonii axes and periderm are preserved in silica—an unusual mode of fossil preservation for Pennslyvanian lycopsid plant remains. The early reports on the Trout Creek lycopsid fossils focused on taxonomic and paleobotanical aspects. Our 2019 reinvestigation of the locality produced many new specimens and a wealth of new data from a variety of analytical methods. Optical microscopy, X-ray diffraction, scanning electron microscopy, energy dispersive electron spectroscopy, determination of specific gravity, and Loss on Ignition provide details of mineralization. Cell walls are preserved with very small fine quartz particles, and cell lumina are filled with microcrystalline quartz. Some cell exteriors are encrusted with euhedral quartz crystals. These multiple forms of quartz are evidence that petrifaction involved several episodes of silicification. The dark color of the fossil wood and siliceous matrix appears to be caused by traces of dispersed carbon, but 500 °C Loss on Ignition reveals that the fossil wood preserves only very small amounts of the original organic matter. Full article
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Open AccessArticle
Analysis of Flood Storage Area Operations in Huai River Using 1D and 2D River Simulation Models Coupled with Global Optimization Algorithms
Geosciences 2019, 9(12), 509; https://doi.org/10.3390/geosciences9120509 (registering DOI) - 06 Dec 2019
Abstract
This article addresses the issue of flood management using four flood storage areas in the middle section of Huai River in China which protect the important downstream city of Bengbu. The same areas are also used by the local population as residential and [...] Read more.
This article addresses the issue of flood management using four flood storage areas in the middle section of Huai River in China which protect the important downstream city of Bengbu. The same areas are also used by the local population as residential and agricultural zones. An optimization problem is therefore posed, with two objectives of simultaneously minimizing the downstream flood risk in Bengbu city and the storage areas’ economic damages. The methodology involved development of river flood models using HEC-RAS, with varying complexity, such as 1-dimensional (1D) model with storage areas represented as lumped conceptual reservoirs, and 2-dimensional (2D) models with detailed representation of the terrain, land-use and hydrodynamics in the storage areas. Experiments of coupling these models with global optimization algorithms (NSGA-II, PESA-II and SPEA-II) were performed (using the HEC-RAS Controller), in which the two objective functions were minimized, while using stage differences between the river and the storage areas as decision variables for controlling the opening / closing of the gates at the lateral structures that link the river with the storage areas. The comparative analysis of the results indicate that more refined optimal operational strategies that spread the damages across all storage areas can be obtained only with the detailed flood simulation models, regardless of the optimization algorithm used. Full article
(This article belongs to the Special Issue Impacts of Compound Hydrological Hazards or Extremes)
Open AccessArticle
Fracture Seismic: Mapping Subsurface Connectivity
Geosciences 2019, 9(12), 508; https://doi.org/10.3390/geosciences9120508 (registering DOI) - 06 Dec 2019
Abstract
Fracture seismic is the method for recording and analyzing passive seismic data for mapping the fractures in the subsurface. Fracture seismic is able to map the fractures because of two types of mechanical actions in the fractures. First, in cohesive rock, fractures can [...] Read more.
Fracture seismic is the method for recording and analyzing passive seismic data for mapping the fractures in the subsurface. Fracture seismic is able to map the fractures because of two types of mechanical actions in the fractures. First, in cohesive rock, fractures can emit short duration energy pulses when growing at their tips through opening and shearing. The industrial practice of recording and analyzing these short duration events is commonly called micro-seismic. Second, coupled rock–fracture–fluid interactions take place during earth deformations and this generates signals unique to the fracture’s physical characteristics. This signal appears as harmonic resonance of the entire, fluid-filled fracture. These signals can be initiated by both external and internal changes in local pressure, e.g., a passing seismic wave, tectonic deformations, and injection during a hydraulic well treatment. Fracture seismic is used to map the location, spatial extent, and physical characteristics of fractures. The strongest fracture seismic signals come from connected fluid-pathways. Fracture seismic observations recorded before, during, and after hydraulic stimulations show that such treatments primarily open pre-existing fractures and weak zones in the rocks. Time-lapse fracture seismic methods map the flow of fluids in the rocks and reveal how the reservoir connectivity changes over time. We present examples that support these findings and suggest that the fracture seismic method should become an important exploration, reservoir management, production, and civil safety tool for the subsurface energy industry. Full article
Open AccessReview
The Carbon-Isotope Record of the Sub-Seafloor Biosphere
Geosciences 2019, 9(12), 507; https://doi.org/10.3390/geosciences9120507 - 05 Dec 2019
Abstract
Sub-seafloor microbial environments exhibit large carbon-isotope fractionation effects as a result of microbial enzymatic reactions. Isotopically light, dissolved inorganic carbon (DIC) derived from organic carbon is commonly released into the interstitial water due to microbial dissimilatory processes prevailing in the sub-surface biosphere. Much [...] Read more.
Sub-seafloor microbial environments exhibit large carbon-isotope fractionation effects as a result of microbial enzymatic reactions. Isotopically light, dissolved inorganic carbon (DIC) derived from organic carbon is commonly released into the interstitial water due to microbial dissimilatory processes prevailing in the sub-surface biosphere. Much stronger carbon-isotope fractionation occurs, however, during methanogenesis, whereby methane is depleted in 13C and, by mass balance, DIC is enriched in 13C, such that isotopic distributions are predominantly influenced by microbial metabolisms involving methane. Methane metabolisms are essentially mediated through a single enzymatic pathway in both Archaea and Bacteria, the Wood–Ljungdahl (WL) pathway, but it remains unclear where in the pathway carbon-isotope fractionation occurs. While it is generally assumed that fractionation arises from kinetic effects of enzymatic reactions, it has recently been suggested that partial carbon-isotope equilibration occurs within the pathway of anaerobic methane oxidation. Equilibrium fractionation might also occur during methanogenesis, as the isotopic difference between DIC and methane is commonly on the order of 75‰, which is near the thermodynamic equilibrium. The isotopic signature in DIC and methane highly varies in marine porewaters, reflecting the distribution of different microbial metabolisms contributing to DIC. If carbon isotopes are preserved in diagenetic carbonates, they may provide a powerful biosignature for the conditions in the deep biosphere, specifically in proximity to the sulphate–methane transition zone. Large variations in isotopic signatures in diagenetic archives have been found that document dramatic changes in sub-seafloor biosphere activity over geological time scales. We present a brief overview on carbon isotopes, including microbial fractionation mechanisms, transport effects, preservation in diagenetic carbonate archives, and their implications for the past sub-seafloor biosphere and its role in the global carbon cycle. We discuss open questions and future potentials of carbon isotopes as archives to trace the deep biosphere through time. Full article
(This article belongs to the Special Issue Tracking the Deep Biosphere through Time)
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Open AccessReview
Antarctic Sea Ice Proxies from Marine and Ice Core Archives Suitable for Reconstructing Sea Ice over the past 2000 Years
Geosciences 2019, 9(12), 506; https://doi.org/10.3390/geosciences9120506 - 04 Dec 2019
Abstract
Dramatic changes in sea ice have been observed in both poles in recent decades. However, the observational period for sea ice is short, and the climate models tasked with predicting future change in sea ice struggle to capture the current Antarctic trends. Paleoclimate [...] Read more.
Dramatic changes in sea ice have been observed in both poles in recent decades. However, the observational period for sea ice is short, and the climate models tasked with predicting future change in sea ice struggle to capture the current Antarctic trends. Paleoclimate archives, from marine sedimentary records and coastal Antarctic ice cores, provide a means of understanding sea ice variability and its drivers over decadal to centennial timescales. In this study, we collate published records of Antarctic sea ice over the past 2000 years (2 ka). We evaluate the current proxies and explore the potential of combining marine and ice core records to produce multi-archive reconstructions. Despite identifying 92 sea ice reconstructions, the spatial and temporal resolution is only sufficient to reconstruct circum-Antarctic sea ice during the 20th century, not the full 2 ka. Our synthesis reveals a 90 year trend of increasing sea ice in the Ross Sea and declining sea ice in the Bellingshausen, comparable with observed trends since 1979. Reconstructions in the Weddell Sea, the Western Pacific and the Indian Ocean reveal small negative trends in sea ice during the 20th century (1900–1990), in contrast to the observed sea ice expansion in these regions since 1979. Full article
Open AccessArticle
Water, Hydrous Melting, and Teleseismic Signature of the Mantle Transition Zone
Geosciences 2019, 9(12), 505; https://doi.org/10.3390/geosciences9120505 - 04 Dec 2019
Abstract
Recent geophysical and petrological observations indicate the presence of water and hydrous melts in and around the mantle transition zone (MTZ), for example, prominent low-velocity zones detected by seismological methods. Experimental data and computational predictions describe the influence of water on elastic properties [...] Read more.
Recent geophysical and petrological observations indicate the presence of water and hydrous melts in and around the mantle transition zone (MTZ), for example, prominent low-velocity zones detected by seismological methods. Experimental data and computational predictions describe the influence of water on elastic properties of mantle minerals. Using thermodynamic relationships and published databases, we calculated seismic velocities and densities of mantle rocks in and around the MTZ in the presence of water for a plausible range of mantle potential temperatures. We then computed synthetic receiver functions to explore the influence of different water distribution patterns on the teleseismic signature. The results may improve our understanding and interpretation of seismic observations of the MTZ. Full article
(This article belongs to the Section Geophysics)
Open AccessReview
An Overview of Opportunities for Machine Learning Methods in Underground Rock Engineering Design
Geosciences 2019, 9(12), 504; https://doi.org/10.3390/geosciences9120504 - 02 Dec 2019
Abstract
Machine learning methods for data processing are gaining momentum in many geoscience industries. This includes the mining industry, where machine learning is primarily being applied to autonomously driven vehicles such as haul trucks, and ore body and resource delineation. However, the development of [...] Read more.
Machine learning methods for data processing are gaining momentum in many geoscience industries. This includes the mining industry, where machine learning is primarily being applied to autonomously driven vehicles such as haul trucks, and ore body and resource delineation. However, the development of machine learning applications in rock engineering literature is relatively recent, despite being widely used and generally accepted for decades in other risk assessment-type design areas, such as flood forecasting. Operating mines and underground infrastructure projects collect more instrumentation data than ever before, however, only a small fraction of the useful information is typically extracted for rock engineering design, and there is often insufficient time to investigate complex rock mass phenomena in detail. This paper presents a summary of current practice in rock engineering design, as well as a review of literature and methods at the intersection of machine learning and rock engineering. It identifies gaps, such as standards for architecture, input selection and performance metrics, and areas for future work. These gaps present an opportunity to define a framework for integrating machine learning into conventional rock engineering design methodologies to make them more rigorous and reliable in predicting probable underlying physical mechanics and phenomenon. Full article
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Open AccessEditorial
Interdisciplinary Geosciences Perspectives of Tsunami Volume 2
Geosciences 2019, 9(12), 503; https://doi.org/10.3390/geosciences9120503 - 28 Nov 2019
Abstract
Disaster related research has its own interdisciplinary perspectives connected to the disaster cycle (response, recovery, prevention, and preparedness). This special issue focuses on interdisciplinary geosciences perspectives of tsunami that cover the whole process of tsunami disasters (generation, propagation, impact assessment, psychological perspectives, and [...] Read more.
Disaster related research has its own interdisciplinary perspectives connected to the disaster cycle (response, recovery, prevention, and preparedness). This special issue focuses on interdisciplinary geosciences perspectives of tsunami that cover the whole process of tsunami disasters (generation, propagation, impact assessment, psychological perspectives, and planning). This special issue collects tsunami research papers not only as lessons from the 2011 Great East Japan tsunami, but also from other areas in Japan (coastal defense structures, tsunami fires, economic loss assessment, and emergency planning) as well as other countries (morphological changes in Indonesia and building risk assessment in New Zealand. The order of the paper follows the tsunami disaster process and the connections between each paper show the interdisciplinary perspectives of tsunami research, which can also be used as a framework for other types of disaster research. Full article
(This article belongs to the Special Issue Interdisciplinary Geosciences Perspectives of Tsunami Volume 2)
Open AccessArticle
Why Are There No Earthquakes in the Intracratonic Paris Basin? Insights from Flexural Models
Geosciences 2019, 9(12), 502; https://doi.org/10.3390/geosciences9120502 - 28 Nov 2019
Abstract
Comparing nearby areas with contrasted seismicity distributions like the French Variscan Armorican Massif (AM) and the surrounding intracratonic Paris Basin (PB) can help deciphering which parameters control the occurrence or absence of diffuse, intraplate seismicity. In this paper, we examine how lithosphere temperature, [...] Read more.
Comparing nearby areas with contrasted seismicity distributions like the French Variscan Armorican Massif (AM) and the surrounding intracratonic Paris Basin (PB) can help deciphering which parameters control the occurrence or absence of diffuse, intraplate seismicity. In this paper, we examine how lithosphere temperature, fluid pressure, and frictional strength variations, combined with horizontal and bending stresses, may condition brittle, ductile or elastic behaviours of the crust in the AM and PB. We compute yield stress envelopes (YSE) and lithospheric flexure across a 1000 km-long SW–NE profile crossing the AM and PB approximately parallel to the direction of the minimum horizontal stress. Flexural models slightly better fit measured Bouguer gravity data if we apply two vertical loads on the AM and PB, with values (positive downward) ranging between −3 and −2.1012, and between 4 and 6.1012 N.m-2, respectively, depending on the chosen crustal composition. Our results evidence that whatever the crustal composition, bending stresses and heat flow variations alone are not sufficient to explain the difference in seismogenic behaviour between the AM and the PB. Variations in friction coefficient, in the range of standard values, are not totally satisfying either, since they do not restrain the brittle crustal thickness in the PB to less than 10 km, which is still large enough to be the locus of shallow earthquakes. Oppositely, increasing the cohesion from 10 to 80 MPa has a stronger effect on the thickness of the brittle upper crust, decreasing it from 10 to 15 km beneath the AM to 0–5 km beneath the PB. This suggests that the Mesozoic sedimentary pile can act as a sticky layer holding together basement rocks of the PB, which is equivalent to an increase in cohesion, and protects them from failure. Full article
(This article belongs to the Special Issue Active Deformation and Rheology of the Continental Lithosphere)
Open AccessArticle
A Quantitative Evaluation of Hyperpycnal Flow Occurrence in a Temperate Coastal Zone: The Example of the Salerno Gulf (Southern Italy)
Geosciences 2019, 9(12), 501; https://doi.org/10.3390/geosciences9120501 - 28 Nov 2019
Abstract
 The inner continental shelf is regarded as a repository of hyperpycnal flow (HF) deposits the analysis of which may contribute to hydrogeological risk assessment in coastal areas. In line with the source to sink paradigm, we examined the dynamics of the coastal watersheds [...] Read more.
 The inner continental shelf is regarded as a repository of hyperpycnal flow (HF) deposits the analysis of which may contribute to hydrogeological risk assessment in coastal areas. In line with the source to sink paradigm, we examined the dynamics of the coastal watersheds facing the Salerno Gulf (Southern Tyrrhenian Sea) in generating hyperpycnal flows and investigated the shallow marine sediment record to verify their possible occurrence in the recent past. Thus, the morphometric properties (hypsometric integral, hypsometric skewness, hypsometric kurtosis, density skewness and density kurtosis) of the watersheds together with the potential rivers’ discharge and sediment concentration, calculated by applying altitude- and extent -based experimental relations, allowed to detect the rivers that were prone to producing HFs. In the shallow marine environment record of the last 2 kyr, anomalous sedimentation, possibly linked to HF events, was identified by comparing the sand-mud ratio (S/M) down-core—at three sites off the main river mouths—to the expected S/M calculated by applying the relation governing the present-day distribution of sand at the seabed in the Salerno Gulf. A return period of major HF events £ 0.1 kyr can be inferred for rivers which fall into the category “dirty rivers”. In these cases, the watersheds have a hypsometric index ranging between 0.2 and 0.3, coastal plains not exceeding 30% of the entire catchment area and a maximum topographic height ³1000 m. A return period of about 0.3 kyr has been inferred for the “moderately dirty rivers”. In these other cases, about 50% of the watersheds develop into a low gradient coastal plain and have a hypsometric index ranging between 0.09 and 0.2. The observations on land and offshore have been complemented to reach a more comprehensive vision of the coastal area dynamics. The method here proposed corroborates the effectiveness of the source to sink approach and is applicable to analogous sediment records in temperate continental shelves which encompass the last 3 kyr, a time interval in which the oscillations of relative sea level can be overlooked. Full article
(This article belongs to the Section Natural Hazards)
Open AccessArticle
Topographic Base Maps from Remote Sensing Data for Engineering Geomorphological Modelling: An Application on Coastal Mediterranean Landscape
Geosciences 2019, 9(12), 500; https://doi.org/10.3390/geosciences9120500 - 27 Nov 2019
Abstract
Coastal landscapes are one of the most changeable areas of the earth's surface. Given this spatial complexity and temporal variability, the construction of reference maps useful for geo-engineering is a challenge. In order to improve the performance of geomorphic models, reliable multiscale and [...] Read more.
Coastal landscapes are one of the most changeable areas of the earth's surface. Given this spatial complexity and temporal variability, the construction of reference maps useful for geo-engineering is a challenge. In order to improve the performance of geomorphic models, reliable multiscale and multi-temporal base maps and Digital Elevation Models (DEM) are needed. The work presented in this paper addresses this issue using an inter-geo-disciplinary approach to optimize the processing of multisource and multi-temporal data and DEMs by using field surveys, conceptual model, and analytical computation on a test area. The data acquired with two surveying techniques were analyzed and compared: Aerial Laser Scanning (ALS) and photogrammetry from stereo pairs of High-Resolution Satellite Images (HRSI). To assess the reliability of the DEMs produced from point clouds, the residuals between the point cloud and the interpolated filtered surface were identified and analyzed statistically. In addition to the contour maps, some feature maps such as slope, planar, and profile curvature maps were produced and analyzed. The frequency distribution of the slope and curvature values were compared with the diffusion, advection, and stream power model, revealing a good agreement with the past and present geomorphic processes acting on the different parts of the study area. Moreover, the integrated geomatics–geomorphic analysis of the outliers’ map showed a good correspondence (more than 75%) between the identified outliers and some specific geomorphological features, such as micro-landforms, which are significant for erosive and gravity-driven mechanisms. The different distribution of the above singularities by different data sources allowed us to attribute their spatial model to the temporal variation of the topography and, consequently, to the geomorphic changes, rather than to the different accuracy. For monitoring purposes and risk mitigation activities, the methodology adopted seems to meet the requirements to make a digital mapping of the coast analyzed, characterized by a rapid evolution of the surface, and can be extended to other stretches of coast with similar characteristics. Full article
(This article belongs to the Special Issue Geodesy and Geomatics Engineering)
Open AccessArticle
Late Orogenic Heating of (Ultra)High Pressure Rocks: Slab Rollback vs. Slab Breakoff
Geosciences 2019, 9(12), 499; https://doi.org/10.3390/geosciences9120499 - 27 Nov 2019
Abstract
Some (ultra)high-pressure metamorphic rocks that formed during continental collision preserve relict minerals, indicating a two-stage evolution: first, subduction to mantle depths and exhumation to the lower-crustal level (with simultaneous cooling), followed by intensive heating that can be characterized by a β-shaped pressure–temperature–time (P–T–t) [...] Read more.
Some (ultra)high-pressure metamorphic rocks that formed during continental collision preserve relict minerals, indicating a two-stage evolution: first, subduction to mantle depths and exhumation to the lower-crustal level (with simultaneous cooling), followed by intensive heating that can be characterized by a β-shaped pressure–temperature–time (P–T–t) path. Based on a two-dimensional (2D) coupled petrological–thermomechanical tectono-magmatic numerical model, we propose a possible sequence of tectonic stages that could lead to these overprinting metamorphic events along an orogenic β-shaped P–T–t path: the subduction and exhumation of continental crust, followed by slab retreat that leads to extension and subsequent asthenospheric upwelling. During the last stage, the exhumed crustal material at the crustmantle boundary undergoes heating from the underlying hot asthenospheric mantle. This slab rollback scenario is further compared numerically with the classical continental collision scenario associated with slab breakoff, which is often used to explain the late heating impulse in the collisional orogens. The mantle upwelling occurring in the experiments with slab breakoff, which is responsible for the heating of the exhumed crustal material, is not related to the slab breakoff but can be caused either by slab bending before slab breakoff or by post-breakoff exhumation of the subducted crust. Our numerical modeling predictions align well with a variety of orogenic P–T–t paths that have been reported from many Phanerozoic collisional orogens, such as the Variscan Bohemian Massif, the Triassic Dabie Shan, the Cenozoic Northwest Himalaya, and some metamorphic complexes in the Alps. Full article
(This article belongs to the Special Issue Active Deformation and Rheology of the Continental Lithosphere)
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Open AccessArticle
New Information on the Madagascan Middle Jurassic Sauropod Lapparentosaurus madagascariensis
Geosciences 2019, 9(12), 498; https://doi.org/10.3390/geosciences9120498 - 27 Nov 2019
Abstract
The systematic position of the Middle Jurassic sauropod Lapparentosaurus madagascariensis is not fully understood due to a lack of useful anatomical detail. Despite many new bone fragments from the axial skeleton, post-cranial skeleton, and a hind limb having been previously unearthed, its systematic [...] Read more.
The systematic position of the Middle Jurassic sauropod Lapparentosaurus madagascariensis is not fully understood due to a lack of useful anatomical detail. Despite many new bone fragments from the axial skeleton, post-cranial skeleton, and a hind limb having been previously unearthed, its systematic position has not yet been satisfactorily established. Although this Malagasy taxon is only recognised by two autapomorphies located in the scapula and coracoid, two features of the neural spine, which are reported here, provide additional information on the common autapomorphies shared with the British genus Cetiosaurus. A full description of the femur and neural spine helps to determine some aspects of its relationship to other similar taxa. Remains of Lapparentosaurus madagascariensis have been recovered from mixed facies that may have been deposited in a shallow water lagoon during a transgressive period in the Isallo IIIb subunit in the Majunga Basin. Full article
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Open AccessCommunication
Investigation of Landslides that Occurred in August on the Chengdu–Kunming Railway, Sichuan, China
Geosciences 2019, 9(12), 497; https://doi.org/10.3390/geosciences9120497 - 26 Nov 2019
Abstract
This paper reports on a large-scale landslide with a movement of 48 thousand m3 of soil and rock that occurred in Sichuan, China. This catastrophic landslide occurred in Aidai village, Ganluo County, at 12:44 on 14 August 2019, blocking a section of [...] Read more.
This paper reports on a large-scale landslide with a movement of 48 thousand m3 of soil and rock that occurred in Sichuan, China. This catastrophic landslide occurred in Aidai village, Ganluo County, at 12:44 on 14 August 2019, blocking a section of the railway between Lianghong station and Aidai station. This landslide resulted in 12 deaths and five people missing. This report describes the preliminary investigation, the rescue activity, topographic survey and analysis as well as the main predisposing and triggering factors. The combined effects of steep topography, continuous rainstorms, floods eroding the foothills of the mountain and human activity were the main influencing factors that triggered this landslide. To reduce the possibility of casualties resulting from large geological disasters, such as landslides and mudslides, in this region in the future, some recommendations are proposed to systematically reduce potential human casualties and economic losses. Full article
(This article belongs to the Section Natural Hazards)
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Open AccessArticle
Discrete Fracture Network Modelling in Triassic–Jurassic Carbonates of NW Lurestan, Zagros Fold-and-Thrust Belt, Iran
Geosciences 2019, 9(12), 496; https://doi.org/10.3390/geosciences9120496 - 26 Nov 2019
Abstract
In this study, discrete fracture network (DFN) modelling was performed for Triassic–Jurassic analogue reservoir units of the NW Lurestan region, Iran. The modelling was elaborated following a multi-scale statistical sampling of the fracture systems characterising the analysed succession. The multi-scale approach was performed [...] Read more.
In this study, discrete fracture network (DFN) modelling was performed for Triassic–Jurassic analogue reservoir units of the NW Lurestan region, Iran. The modelling was elaborated following a multi-scale statistical sampling of the fracture systems characterising the analysed succession. The multi-scale approach was performed at two different observation scales. At the macro-scale, a digital outcrop analysis was carried out by means of a digital line-drawing based on camera-acquired images, focussing on the distribution of major throughgoing fractures; at the meso-scale, the scan line method was applied to investigate the background fractures of the examined formations. The gathered data were statistically analysed in order to estimate the laws governing the statistical distribution of some key fracture set attributes, namely, spacing, aperture, and height. The collected dataset was used for the DFN modelling, allowing the evaluation of the relative connectivity of the fracture systems and, therefore, defining the architecture and the geometries within the fracture network. The performed fracture modelling, confirmed, once again, the crucial impact that large-scale throughgoing fractures have on the decompartmentalization of a reservoir and on the related fluid flow migration processes. The derived petrophysical properties distribution showed in the models, defined the Kurra Chine Fm. and, especially, the Sehkaniyan Fm. as good-quality reservoir units, whereas the Sarki Fm was considered a poor-quality reservoir unit. Full article
(This article belongs to the Special Issue Characterization and Simulation of Carbonate Reservoirs)
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Open AccessArticle
Bentonite Extrusion into Near-Borehole Fracture
Geosciences 2019, 9(12), 495; https://doi.org/10.3390/geosciences9120495 - 25 Nov 2019
Abstract
In this paper, we discuss laboratory experiments of bentonite swelling and coupled finite element simulations to explicate bentonite extrusion. For the experiments, we developed a swell cell apparatus to understand the bentonite migration to the near-borehole fracture. We constructed the swell cell using [...] Read more.
In this paper, we discuss laboratory experiments of bentonite swelling and coupled finite element simulations to explicate bentonite extrusion. For the experiments, we developed a swell cell apparatus to understand the bentonite migration to the near-borehole fracture. We constructed the swell cell using acrylic, which comprised of a borehole and open fracture. Initially, the borehole of the swell cell was filled with bentonite and liquid. Then, the apparatus was sealed for observations. Due to the liquid saturation increase of bentonite, its swelling pressure increased. The developed pressure caused the extrusion of bentonite into the fracture, and the flow of bentonite from the borehole decreased with time. Moreover, for the effectiveness of bentonite-based plugging, there is a limiting condition, which represents the relation between the maximum bentonite migration length with the fracture aperture. Additionally, we also performed the bentonite free swelling test to assess the swelling potential to the fluid salinity, and we observed that with the increase of the salinity, the swelling potential decreased. In addition, we present a fully coupled two-phases fluids flow (e.g., liquid and gas) and deformation flow finite element (FE) model for the bentonite column elements and swell cell model. We also combined the Modified Cam Clay (MCC) model and the swelling model for the bentonite deformation flow model. Then, we also present the validation of the bentonite model. To model other sub-domains, we used the poro-elastic model. Additionally, we obtained the transition between the wetting phase (i.e., liquid) and non-wetting phase (i.e., gas) using the Brooks–Corey model. From the finite element results, we observed that due to the liquid intrusion into the bentonite, the developed capillary pressure gradient results in a change of the hydro-mechanical behavior of the bentonite. Initially, we observed that due to the high capillary pressure gradient, the liquid saturation and the swelling pressure increased, which also decreased with time due to a reduction in the capillary pressure gradient. Thereby, the swelling pressure-induced bentonite migration to the fracture also decreased over time, and after the equilibrium state (for a negligible pressure gradient), there was no significant transport of bentonite into the fracture. Full article
(This article belongs to the Special Issue Behavior of Expansive Soils and its Shrinkage Cracking)
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Open AccessArticle
Correlation of Elastic Moduli and Serpentine Content in Ultramafic Rocks
Geosciences 2019, 9(12), 494; https://doi.org/10.3390/geosciences9120494 - 25 Nov 2019
Abstract
Understanding the physical properties of ultramafic rocks is important for evaluating a wide variety of petrologic models of the oceanic lithosphere, particularly upper mantle and lower crust. Hydration of oceanic peridotites results in increasing serpentine content, which affects lithospheric physical properties and the [...] Read more.
Understanding the physical properties of ultramafic rocks is important for evaluating a wide variety of petrologic models of the oceanic lithosphere, particularly upper mantle and lower crust. Hydration of oceanic peridotites results in increasing serpentine content, which affects lithospheric physical properties and the global bio/geochemical cycles of various elements. In understanding tectonic, magmatic, and metamorphic history of the oceanic crust, interpreting seismic velocities, rock composition, and elastic moduli are of fundamental importance. In this study, we show that as serpentine content increases, density decreases linearly with a slope of 7.85. Porosity of the samples does not show any systematic correlation with serpentine content, as it is more strongly affected by local weathering and erosional processes. We also correlate increase in serpentine content with a linear decline in shear, bulk, and Young’s moduli with slopes of 0.48, 0.77, and 0.45, respectively. Our results show that increase in serpentine content of mantle wedge and forearc mantle contributes to their brittle behavior and result in break-offs, obduction, and overthrusting. Therefore, serpentine content strongly affects tectonic processes at subduction zones, particularly serpentinization may be responsible for formation of weak fault zones. Also, serpentinization of fresh oceanic peridotite in slow and ultra-slow spreading ridges may be responsible for observed discontinuities in thin crust. Full article
(This article belongs to the Section Geophysics)
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Open AccessArticle
Landslide Susceptibility Assessment of Mauritius Island (Indian Ocean)
Geosciences 2019, 9(12), 493; https://doi.org/10.3390/geosciences9120493 - 23 Nov 2019
Abstract
This work is focused on the landslide susceptibility assessment, applied to Mauritius Island. The study area is a volcanic island located in the western part of the Indian Ocean and it is characterized by a plateau-like morphology interrupted by three rugged mountain areas. [...] Read more.
This work is focused on the landslide susceptibility assessment, applied to Mauritius Island. The study area is a volcanic island located in the western part of the Indian Ocean and it is characterized by a plateau-like morphology interrupted by three rugged mountain areas. The island is severely affected by geo-hydrological hazards, generally triggered by tropical storms and cyclones. The landslide susceptibility analysis was performed through an integrated approach based on morphometric analysis and preliminary Geographical Information System (GIS)-based techniques, supported by photogeological analysis and geomorphological field mapping. The analysis was completed following a mixed heuristic and statistical approach, integrated using GIS technology. This approach led to the identification of eight landslide controlling factors. Hence, each factor was evaluated by assigning appropriate expert-based weights and analyzed for the construction of thematic maps. Finally, all the collected data were mapped through a cartographic overlay process in order to realize a new zonation of landslide susceptibility. The resulting map was grouped into four landslide susceptibility classes: low, medium, high, and very high. This work provides a scientific basis that could be effectively applied in other tropical areas showing similar climatic and geomorphological features, in order to develop sustainable territorial planning, emergency management, and loss-reduction measures. Full article
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Open AccessReview
Large Russian Lakes Ladoga, Onega, and Imandra under Strong Pollution and in the Period of Revitalization: A Review
Geosciences 2019, 9(12), 492; https://doi.org/10.3390/geosciences9120492 - 22 Nov 2019
Abstract
In this paper, retrospective analyses of long-term changes in the aquatic ecosystem of Ladoga, Onega, and Imandra lakes, situated within North-West Russia, are presented. At the beginning of the last century, the lakes were oligotrophic, freshwater and similar in origin in terms of [...] Read more.
In this paper, retrospective analyses of long-term changes in the aquatic ecosystem of Ladoga, Onega, and Imandra lakes, situated within North-West Russia, are presented. At the beginning of the last century, the lakes were oligotrophic, freshwater and similar in origin in terms of the chemical composition of waters and aquatic fauna. Three stages were identified in this study: reference condition, intensive pollution and degradation, and decreasing pollution and revitalization. Similar changes in polluted bays were detected, for which a significant decrease in their oligotrophic nature, the dominance of eurybiont species, their biodiversity under toxic substances and nutrients, were noted. The lakes have been recolonized by northern species following pollution reduction over the past 20 years. There have been replacements in dominant complexes, an increase in the biodiversity of communities, with the emergence of more southern forms of introduced species. The path of ecosystem transformation during and after the anthropogenic stress compares with the regularities of ecosystem successions: from the natural state through the developmental stage to a more stable mature modification, with significantly different natural characteristics. A peculiarity of the newly formed ecosystems is the change in structure and the higher productivity of biological communities, explained by the stability of the newly formed biogeochemical nutrient cycles, as well as climate warming. Full article
Open AccessArticle
Evaluation of Remote-Sensing based Estimates of Actual Evapotranspiration over (Diverse Shape and Sized) Palmiet Wetlands
Geosciences 2019, 9(12), 491; https://doi.org/10.3390/geosciences9120491 - 22 Nov 2019
Abstract
Accurately quantifying actual evapotranspiration (ETa) over wetlands is important for the improved management of these ecosystems, since 65% of them are threatened by clearing or drainage in South Africa. This study evaluated a range of available estimates of ETa over six palmiet wetlands, [...] Read more.
Accurately quantifying actual evapotranspiration (ETa) over wetlands is important for the improved management of these ecosystems, since 65% of them are threatened by clearing or drainage in South Africa. This study evaluated a range of available estimates of ETa over six palmiet wetlands, which are key ecological structures in terms of water regulation and sediment trapping. The research compared three remote sensing based products (a local product, FruitLook, and two global data products, MOD16 ET and EEFlux) across different rainfall years (2008 to 2019). Their outputs were validated, where possible, with limited ground-based scintillometer data on the Krom palmiet wetland, which indicated that MOD16 and EEFlux were most representative of ground-based measurements. We also compared the small pixel size EEFlux data over three wetlands with ETa over increasing buffers of land cover (100, 500, 1000 m) in order to validate the perception of these wetlands being high water users. While larger wetlands had slightly higher evaporative demands than adjacent areas, ETa over a small wetland was similar to neighboring land cover. The results indicate that palmiet wetland ETa is highly variable and dependent on external factors such as climate, wetland size and seasonality. Full article
(This article belongs to the Section Hydrogeology)
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Open AccessArticle
An Analysis Applying InSAR of Subsidence Caused by Nearby Mining-Induced Earthquakes
Geosciences 2019, 9(12), 490; https://doi.org/10.3390/geosciences9120490 - 21 Nov 2019
Abstract
Earthquake occurrence is usually unpredictable apart from sites in the vicinity of volcanoes. It is not easy to measure displacements caused by seismic phenomena using classical geodetic methods, which are based on point survey. Therefore, the surveying of ground movements caused by seismic [...] Read more.
Earthquake occurrence is usually unpredictable apart from sites in the vicinity of volcanoes. It is not easy to measure displacements caused by seismic phenomena using classical geodetic methods, which are based on point survey. Therefore, the surveying of ground movements caused by seismic events should be carried out continuously. Nowadays, remote sensing data and InSAR are often applied to monitor ground displacements in areas affected by seismicity. The effects of severe nearby mining-induced earthquakes have been discussed in the paper. The earthquakes occurred in 2017 and had a magnitude of 4.7 and 4.8. The distance between the epicenters of the mining-induced earthquakes was around 1.6 km. The aim of the investigation has been to analyze the spatio-temporal distribution of ground movements caused by the two tremors using the InSAR technique. Superposition of surface displacement has been studied in time and space. The main scientific aim has been to prove that in the areas where high-energy tremors occur, ground movements overlap. Due to proximity between the epicenters, the mining-induced earthquakes caused the formation of a large subsidence trough with the dimension of approximately 1.2 km × 4.2 km and total subsidence of ca. 116 mm. Two-time phases of subsidence were determined with temporal overlapping. The subsidence analysis has enhanced the cognition of the impact of mining-induced seismicity on the kinematics of surface changes. Moreover, the present work supports the thesis that InSAR is a valuable and adequately accurate technique to monitor ground displacements caused by mining induced earthquakes. Full article
(This article belongs to the Section Geophysics)
Open AccessArticle
Evaluation of The Seismic Hazard in The Marmara Region (Turkey) Based on Updated Databases
Geosciences 2019, 9(12), 489; https://doi.org/10.3390/geosciences9120489 - 20 Nov 2019
Abstract
The increase in the wealth of information on the seismotectonic structure of the Marmara region after two devastating earthquakes (M7.6 Izmit and M7.2 Duzce events) in the year 1999 opened the way for the reassessment of the probabilistic seismic hazard [...] Read more.
The increase in the wealth of information on the seismotectonic structure of the Marmara region after two devastating earthquakes (M7.6 Izmit and M7.2 Duzce events) in the year 1999 opened the way for the reassessment of the probabilistic seismic hazard in the light of new datasets. In this connection, the most recent findings and outputs of different national and international projects concerning seismicity and fault characterization in terms of geometric and kinematic properties are exploited in the present study to build an updated seismic hazard model. A revised fault segmentation model, alternative earthquake rupture models under a Poisson and renewal assumptions, as well as recently derived global and regional ground motion prediction equations (GMPEs) are put together in the present model to assess the seismic hazard in the region. Probabilistic seismic hazard assessment (PSHA) is conducted based on characteristic earthquake modelling for the fault segments capable of producing large earthquakes and smoothed seismicity modelling for the background smaller magnitude earthquake activity. The time-independent and time-dependent seismic hazard results in terms of spatial distributions of three ground-shaking intensity measures (peak ground acceleration, PGA, and 0.2 s and 1.0 s spectral accelerations (SA) on rock having 10% and 2% probabilities of exceedance in 50 years) as well as the corresponding hazard curves for selected cities are shown and compared with previous studies. Full article
(This article belongs to the Special Issue Seismic Sequence in Mediterranean Region)
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Open AccessArticle
Non-Linear Analysis of Inter-Story Pounding between Wood-Framed Buildings during Ground Motion
Geosciences 2019, 9(12), 488; https://doi.org/10.3390/geosciences9120488 - 20 Nov 2019
Abstract
Pounding between adjacent buildings during ground motion may result in structural damage or lead to total destruction of structures. The research on the phenomenon has recently been much advanced; however, the analyses have been carried out only for concrete, steel, and masonry structures, [...] Read more.
Pounding between adjacent buildings during ground motion may result in structural damage or lead to total destruction of structures. The research on the phenomenon has recently been much advanced; however, the analyses have been carried out only for concrete, steel, and masonry structures, while pounding between wooden buildings has not been studied so far. The aim of this paper is to show the results of detailed non-linear seismic analysis of inter-story pounding between the wood-framed buildings modelled by using the finite element method. Firstly, the modal analysis of the structures was conducted. Then, the detailed non-linear analysis of earthquake-induced collisions between two wood-framed buildings of different heights was carried out. The results of the analysis indicate that the behavior of both structures in the longitudinal as well as in the transverse direction is significantly influenced by interactions. The response of the taller building is increased in both directions. On the other hand, the response of the lower building is decreased in the longitudinal direction, while it is increased in the transverse one. The results of the study presented in the paper indicate that, due to deformability of buildings made of wood, structural interactions may change their responses much more, as compared to steel, reinforced concrete, or masonry structures. Full article
(This article belongs to the Special Issue Geodesy and Geomatics Engineering)
Open AccessArticle
Multidisciplinary Characterization of Chlorinated Solvents Contamination and In-Situ Remediation with the Use of the Direct Current Resistivity and Time-Domain Induced Polarization Tomography
Geosciences 2019, 9(12), 487; https://doi.org/10.3390/geosciences9120487 - 20 Nov 2019
Abstract
Soil contamination is a widespread problem and action needs to be taken in order to prevent damage to the groundwater and the life around the contaminated sites. In Sweden, it is estimated that more than 80,000 sites are potentially contaminated, and therefore, there [...] Read more.
Soil contamination is a widespread problem and action needs to be taken in order to prevent damage to the groundwater and the life around the contaminated sites. In Sweden, it is estimated that more than 80,000 sites are potentially contaminated, and therefore, there is a demand for investigations and further treatment of the soil. In this paper, we present the results from a methodology applied in a site contaminated with chlorinated solvents, for characterization of the contamination in order to plan the remediation and to follow-up the initial step of in-situ remediation in an efficient way. We utilized the results from three different methods; membrane interface probe for direct measurement of the contaminant concentrations; seismic refraction tomography for investigating the depth to the bedrock interface; and direct current resistivity and time-domain induced polarization tomography to acquire a high-resolution imaging of the electrical properties of the subsurface. The results indicate that our methodology is very promising in terms of site characterization, and furthermore, has great potential for real-time geophysical monitoring of contaminated sites in the future. Full article
(This article belongs to the Section Geophysics)
Open AccessArticle
Co-Constructing a Narrative of ‘Never Give Up’ in Preparing for a Mega-Tsunami: An Exemplar of ‘All-Of-Society Engagement’?
Geosciences 2019, 9(12), 486; https://doi.org/10.3390/geosciences9120486 - 20 Nov 2019
Abstract
This paper discusses the ‘all-of-society engagement’ concept promoted in the Sendai Framework for Disaster Risk Reduction (DRR) 2015–2030, drawing on the case of Kuroshio Town, Kochi Prefecture in Japan. The framework does not offer a clear definition of ‘all-of-society engagement’. The paper suggests [...] Read more.
This paper discusses the ‘all-of-society engagement’ concept promoted in the Sendai Framework for Disaster Risk Reduction (DRR) 2015–2030, drawing on the case of Kuroshio Town, Kochi Prefecture in Japan. The framework does not offer a clear definition of ‘all-of-society engagement’. The paper suggests the case of Kuroshio Town could help us envisage what ‘all-of-society engagement’ might look like. The people in the town were shocked to receive the official revised prediction of a forthcoming mega earthquake and tsunami in March 2012, which suggested that the Nankai Trough Earthquake could reach the seismic intensity of seven, and the subsequent tsunami could be as high as 34.4 m in a certain part of Kuroshio Town. Pessimism spread, and an attitude of ‘giving up’ prevailed. Kuroshio Town Hall had to come up with a drastic measure to unite the whole town, which was to present a clear philosophy, rather than technical measures. The narrative of ‘never give up’ was thus constructed, which was gradually appreciated and shared by the residents of the town. The paper teases out this whole-town preparedness project with the use of the four priorities of actions in the Sendai Framework as an analytical tool. The analysis brings certain mechanisms deployed in the town to the fore, which enabled the co-construction of the narrative of ‘never give up’, contributing to motivating the residents to engage in preparedness activities. Full article
(This article belongs to the Special Issue Interdisciplinary Geosciences Perspectives of Tsunami Volume 2)
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