Geosciences

18 pages, 2821 KiB

Open AccessArticle

Augmenting Seafloor Characterization via Grain Size Analysis with Low-Cost Imagery: Minimizing Sediment Sampler Biases and Increasing Habitat Classification Accuracy

by Sean Terrill, Agnes Mittermayr, Bryan Legare and Mark Borrelli

Geosciences 2024, 14(11), 313; https://doi.org/10.3390/geosciences14110313 - 15 Nov 2024

Abstract

Bottom-grab samplers have long been the standard to describe nearshore marine habitats both qualitatively and quantitively. However, sediment samplers are designed to collect specific grain sizes and therefore have biases toward those sediments. Here, we discuss seafloor characterizations based on grain size analysis [...] Read more.

Bottom-grab samplers have long been the standard to describe nearshore marine habitats both qualitatively and quantitively. However, sediment samplers are designed to collect specific grain sizes and therefore have biases toward those sediments. Here, we discuss seafloor characterizations based on grain size analysis alone vs. grain size analysis augmented with quantitative benthic imagery. We also use both datasets to inform a prevalent benthic habitat classification system. The Coastal and Marine Ecological Classification Standard (CMECS) was used to test this hypothesis. CMECS was adopted by the federal government to standardize habitat classification in coastal U.S. waters. CMECS provides a hierarchal framework to define and interpret benthic habitats but does not prescribe specific sampling methods. Photography has been utilized for many decades in benthic ecology but has rarely been employed in habitat classification using CMECS. No study to date has quantitatively examined the benefit of incorporating benthic imagery into the classification of biotopes using CMECS. The objective of this study is to classify a roughly 1 km² subtidal area within Herring Cove in Provincetown, MA with CMECS and quantify the benefit of augmenting classification with low-cost imagery. A benthic habitat survey of the study area included grab sampling for grain-size analysis and invertebrate taxonomy, benthic imagery, water quality sampling at 24 sampling stations, and acoustic mapping of the study area. Multivariate statistical analyses were employed to classify biotic communities and link environmental and biological data to classify biotopes. The results showed that benthic imagery improved the classification and mapping of CMECS components. Furthermore, the classification of habitats and biotopes was improved using benthic imagery data. These findings imply that the incorporation of low-cost benthic imagery is warranted in coastal benthic biotope classification and mapping studies and should be regularly adopted. This study has implications for coastal benthic ecologists classifying benthic habitats within the CMECS framework. Full article

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14 pages, 3937 KiB

Open AccessArticle

Fragility of Highway Embankments Exposed to Permanent Deformations Due to Underlying Fault Rupture

by Eleni Petala and Nikolaos Klimis

Geosciences 2024, 14(11), 312; https://doi.org/10.3390/geosciences14110312 - 15 Nov 2024

Abstract

Seismic risk expresses the expected degree of damage and loss following a catastrophic event. An efficient tool for assessing the seismic risk of embankments is fragility curves. This research investigates the influence of embankment’s geometry, the depth of rupture occurrence, and the underlying [...] Read more.

Seismic risk expresses the expected degree of damage and loss following a catastrophic event. An efficient tool for assessing the seismic risk of embankments is fragility curves. This research investigates the influence of embankment’s geometry, the depth of rupture occurrence, and the underlying sandy soil’s conditions on the embankment’s fragility. To achieve this, the response of three highway embankments resting on sandy soil was examined through quasi-static parametric numerical analyses. For the establishment of fragility curves, a cumulative lognormal probability distribution function was used. The maximum vertical displacement of the embankments’ external surface and the fault displacement were considered as the damage indicator and the intensity measure, respectively. Damage levels were categorized into three qualitative thresholds: minor, moderate, and extensive. All fragility curves were generated for normal and reverse faults, as well as the combination of those fault types (dip-slip fault). Finally, the proposed curves were verified via their comparison with those provided by HAZUS. It was concluded that embankment geometry and depth of fault rupture appearance do not significantly affect fragility, as exceedance probabilities show minimal differences (<4%). However, an embankment founded on dense sandy soil reveals slightly higher fragility compared to the one founded on loose sand. Differences regarding the probability of exceedance of a certain damage level are restricted by a maximum of 7%. Full article

(This article belongs to the Section Natural Hazards)

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14 pages, 7013 KiB

Open AccessArticle

Earthquake Environmental Effects: The Case of Late Classical-Hellenistic Helike, Gulf of Corinth, Greece

by Dora Katsonopoulou and Ioannis Koukouvelas

Geosciences 2024, 14(11), 311; https://doi.org/10.3390/geosciences14110311 - 15 Nov 2024

Abstract

Human habitat is much controlled by the landscape and its ongoing processes overtime. Some of these processes occur instantaneously and are often triggered by seismic events with a major destructive impact on the human-built environment. Helike, on the southwest shore of the Gulf [...] Read more.

Human habitat is much controlled by the landscape and its ongoing processes overtime. Some of these processes occur instantaneously and are often triggered by seismic events with a major destructive impact on the human-built environment. Helike, on the southwest shore of the Gulf of Corinth, is a characteristic case of an ancient habitation site bearing witness to repetitious natural disasters from the Early Bronze Age to the Late Antiquity. The Late Classical-Hellenistic site, revived in the Helike plain after the 373 BC earthquake, has been systematically investigated thanks to the multidisciplinary research and excavations of the Helike Project in the last 35 years. This work has significantly enriched the historical seismicity of the region and shed light on past human-environment relationships. The study of the architectural remains excavated by the Helike Project, coupled with geological and soil micromorphological analysis on archaeological soils and sediments of the settlement, demonstrates a constant effort of the Helike people to reconcile with the elements of nature. Our results underline the destruction of a flourishing textile dyeworks operated at the settlement, due to a strong earthquake which triggered extensive morphological changes in a broader area. These changes include co-seismic liquefaction and lateral spreading, and post-seismic changes in the gradient of river channels. The former changes attest to an uplift in the headwater area and subsidence in the lowland plain of the ravine flowing near the ancient site. Full article

(This article belongs to the Section Natural Hazards)

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17 pages, 6592 KiB

Open AccessArticle

Determining the Boundaries of Overlying Strata Collapse Above Mined-Out Panels of Zhomart Mine Using Seismic Data

by Sara Istekova, Alexander Makarov, Dina Tolybaeva, Arman Sirazhev and Kuanysh Togizov

Geosciences 2024, 14(11), 310; https://doi.org/10.3390/geosciences14110310 - 15 Nov 2024

Abstract

The present article is devoted to the issue of studying the patterns of displacement of superincumbent rock over panels of a mine obtained using advanced seismic technologies, allowing for the study of the boundaries of caving zones in the depths of rock mass. [...] Read more.

The present article is devoted to the issue of studying the patterns of displacement of superincumbent rock over panels of a mine obtained using advanced seismic technologies, allowing for the study of the boundaries of caving zones in the depths of rock mass. A seismic exploration has been performed in local areas of Zhomart mine responsible for the development of Zhaman-Aybat cuprous sandstone deposits in Central Kazakhstan at the stage of repeated mining with pulling of previously non-mined ore pillars and superincumbent rock caving. A 2D field seismic exploration has been accomplished, totaling to 8000-line m of seismic lines using seismic shot point. The survey depth varied from 455 m to 625 m. The state-of-the-art technologies of kinematic and dynamic analysis of wavefield have been widely used during data processing and interpretation targeted at identifying anomalies associated with the structural heterogeneity of the pays and rock mass, engaging modern algorithms and mathematical apparatuses of specialized geodata processing systems. The above effort resulted in new data regarding the location and morphology of the reflectors, characterizing geological heterogeneity of the section, zones of smooth rock displacement, and displacement of strata with significant disturbance of the rocks overlying mined-out productive pay. The potential of the application of modern 2D seismic exploration to studying an underworked zone with altered physical and mechanical properties located over an ore deposit has been assessed. The novelty and practical significance of the research lies in the determination of the boundaries of zones of displacement and superincumbent rock caving over the panels obtained using state-of-the-art technologies of seismic exploration. The deliverables may be used to improve the process of recognizing specific types of technogenic heterogeneities in the rock mass, impacting the efficiency and safety of subsurface ore mining, both for localization and mining monitoring. Full article

(This article belongs to the Section Geophysics)

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14 pages, 15198 KiB

Open AccessArticle

Refining Heterogeneities near the Core–Mantle Boundary Beneath East Pacific Regions: Enhanced Differential Travel-Time Analysis Using USArray

by Yenting (Justin) Ko and Kai-Jie Hu

Geosciences 2024, 14(11), 309; https://doi.org/10.3390/geosciences14110309 - 14 Nov 2024

Abstract

Recent advancements in seismic data analysis have enhanced our grasp of the seismic heterogeneities near the core–mantle boundary (CMB). Through seismic tomography, persistent lower-mantle structures like the large low shear velocity provinces (LLSVPs) beneath the Pacific and South Africa have been identified. However, [...] Read more.

Recent advancements in seismic data analysis have enhanced our grasp of the seismic heterogeneities near the core–mantle boundary (CMB). Through seismic tomography, persistent lower-mantle structures like the large low shear velocity provinces (LLSVPs) beneath the Pacific and South Africa have been identified. However, variations in the finer-scale features across different models raise questions about their origins. This study utilizes differential travel-time measurements from the USArray, operational across the contiguous United States from 2007 to 2014, to examine the impact of upper-mantle heterogeneities on tomographic models. By averaging the P-wave travel times and calibrating them with diffracted P-waves at the same stations, we mitigate the effects of shallow heterogeneities. The findings confirm that this method accurately maps the seismic anomalies beneath the USArray, consistent with other North American studies. Calibrated Pdiff travel-time data indicate significant anomalies in the mid-Pacific and Bering Sea and lesser anomalies in the northern Pacific, aligning with the global tomographic images. Moreover, the study highlights sharp travel-time variations over short distances, such as those across the northern boundary of the mid-Pacific anomaly, suggesting a chemically heterogeneous Pacific LLSVP. Full article

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22 pages, 12163 KiB

Open AccessArticle

Assessing the Use of Electrical Resistivity for Monitoring Crude Oil Contaminant Distribution in Unsaturated Coastal Sands Under Varying Salinity

by Margaret A. Adeniran, Michael A. Oladunjoye and Kennedy O. Doro

Geosciences 2024, 14(11), 308; https://doi.org/10.3390/geosciences14110308 - 14 Nov 2024

Abstract

Monitoring crude oil spills in coastal areas is challenging due to limitations in traditional in situ methods. Electrical resistivity imaging (ERI) offers a high-resolution approach to monitoring the subsurface spatial distribution of crude oil, but its effectiveness in highly-resistive, unsaturated coastal sands with [...] Read more.

Monitoring crude oil spills in coastal areas is challenging due to limitations in traditional in situ methods. Electrical resistivity imaging (ERI) offers a high-resolution approach to monitoring the subsurface spatial distribution of crude oil, but its effectiveness in highly-resistive, unsaturated coastal sands with varying salinity remains unexplored. This study assessed the effectiveness of ERI for monitoring crude oil spills in sandy soil using a 200 × 60 × 60 cm 3D sandbox filled with medium-fine-grained sand under unsaturated conditions. Two liters of crude oil were spilled under controlled conditions and monitored for 48 h using two surface ERI transects with 98 electrodes spaced every 2 cm and a dipole–dipole electrode array. The influence of varying salinity was simulated by varying the pore-fluid conductivities at four levels (0.6, 20, 50, and 85 mS/cm). After 48 h, the results show a percentage resistivity increase of 980%, 280%, 142%, and 70% for 0.6, 20, 50, and 85 mS/cm, respectively. The crude oil migration patterns varied with porewater salinity as higher salinity enhanced the crude oil retention at shallow depth. High salinity produces a smaller resistivity contrast, thus limiting the sensitivity of ERI in detecting the crude oil contaminant. These findings underscore the need to account for salinity variations when designing remediation strategies, as elevated salinity may restrict crude oil migration, resulting in localized contaminations. Full article

(This article belongs to the Section Geophysics)

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16 pages, 9462 KiB

Open AccessArticle

Seismic Risk Assessment for the City of Sofia, Bulgaria

by Dimcho Enchev Solakov, Dimitar Stefanov, Stela Simeonova and Plamena Raykova-Tsankova

Geosciences 2024, 14(11), 307; https://doi.org/10.3390/geosciences14110307 - 13 Nov 2024

Abstract

An earthquake is the most destructive natural phenomenon, with its sudden onset and rapid spread impacting large areas. Among the various geohazards, seismic ones dominate in terms of their social and economic effects on human life and the urban environment. In the present [...] Read more.

An earthquake is the most destructive natural phenomenon, with its sudden onset and rapid spread impacting large areas. Among the various geohazards, seismic ones dominate in terms of their social and economic effects on human life and the urban environment. In the present study, a deterministic earthquake ground motion scenario for the city of Sofia (the capital of Bulgaria) is presented. The earthquake risk posed to Sofia is quantified by considering the city’s seismic context, which contributes to its hazard and risk. The assessment of seismic hazards and the generation of earthquake scenarios make up the first step of seismic risk evaluations, as risk reduction strategies can only be developed with a better understanding of these threats. Risk assessment and its associated management comprise the most effective approach to estimating the impact of seismic hazards on the city of Sofia, which exhibits high seismic activity. Our findings provide a basis for local governments to review their susceptibility and preparedness. The consideration of earthquake scenarios in the creation of policies for seismic risk reduction will allow us to focus on the prevention of earthquake effects rather than on the activities following these disasters. Full article

(This article belongs to the Special Issue Applied Geophysics for Geohazards Investigations)

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22 pages, 4068 KiB

Open AccessArticle

Analysis of the Liquefaction Potential at the Base of the San Marcos Dam (Cayambe, Ecuador)—A Validation in the Use of the Horizontal-to-Vertical Spectral Ratio

by Olegario Alonso-Pandavenes, Francisco Javier Torrijo and Gabriela Torres

Geosciences 2024, 14(11), 306; https://doi.org/10.3390/geosciences14110306 - 13 Nov 2024

Abstract

Ground liquefaction potential analysis is a fundamental characterization in areas with continuous seismic activity, such as Ecuador. Geotechnical liquefaction studies are usually approached from dynamic penetration tests, which pose problems both in their correct execution and in their evaluation. Our research involves analyzing [...] Read more.

Ground liquefaction potential analysis is a fundamental characterization in areas with continuous seismic activity, such as Ecuador. Geotechnical liquefaction studies are usually approached from dynamic penetration tests, which pose problems both in their correct execution and in their evaluation. Our research involves analyzing dynamic penetration tests and microtremor geophysical surveys (horizontal-to-vertical spectral ratio technique, HVSR) for analyzing the liquefaction potential at the base of the San Marcos dam, a reservoir located in Cayambe canton (Ecuador). Based on the investigations performed at the time of construction of the dam (drilling and geophysical refraction profiles) and the application of 20 microtremor observation stations via the HVSR technique, an analysis of the safety factor of liquefaction (SF_liq) was conducted using the 2001 Youd and Idriss formulation and the values of the standard penetration test (SPT) applied in granular materials (sands). In addition, the vulnerability index (K_g) proposed by Nakamura in 1989 was analyzed through the HVSR records related to the ground shear strain (GSS). The results obtained in the HVSR analysis indicate the presence of a zone of about 100 m length in the central part of the foot of the dam, whose GSS values identified a condition of susceptibility to liquefaction. In the same area, the SPT essays analysis in the P-8A drill hole also shows a potential susceptibility to liquefaction in earthquake conditions greater than a moment magnitude (M_w) of 4.5. That seismic event could occur in the area, for example, with a new activity condition of the nearby Cayambe volcano or even from an earthquake from the vicinity of the fractured zone. Full article

(This article belongs to the Special Issue Geotechnical Earthquake Engineering and Geohazard Prevention)

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17 pages, 47728 KiB

Open AccessArticle

Accurate Feature Extraction from Historical Geologic Maps Using Open-Set Segmentation and Detection

by Aaron Saxton, Jiahua Dong, Albert Bode, Nattapon Jaroenchai, Rob Kooper, Xiyue Zhu, Dou Hoon Kwark, William Kramer, Volodymyr Kindratenko and Shirui Luo

Geosciences 2024, 14(11), 305; https://doi.org/10.3390/geosciences14110305 - 13 Nov 2024

Abstract

This study presents a novel AI method for extracting polygon and point features from historical geologic maps, representing a pivotal step for assessing the mineral resources needed for energy transition. Our innovative method involves using map units in the legends as prompts for [...] Read more.

This study presents a novel AI method for extracting polygon and point features from historical geologic maps, representing a pivotal step for assessing the mineral resources needed for energy transition. Our innovative method involves using map units in the legends as prompts for one-shot segmentation and detection in geological feature extraction. The model, integrated with a human-in-the-loop system, enables geologists to refine results efficiently, combining the power of AI with expert oversight. Tested on geologic maps annotated by USGS and DARPA for the AI4CMA DARPA Challenge, our approach achieved a median F1 score of 0.91 for polygon feature segmentation and 0.73 for point feature detection when such features had abundant annotated data, outperforming current benchmarks. By efficiently and accurately digitizing historical geologic map, our method promises to provide crucial insights for responsible policymaking and effective resource management in the global energy transition. Full article

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21 pages, 21536 KiB

Open AccessReview

A Review on Uranium Mineralization Related to Na-Metasomatism: Indian and International Examples

by Priyanka Mishra, Manju Sati and Rajagopal Krishnamurthi

Geosciences 2024, 14(11), 304; https://doi.org/10.3390/geosciences14110304 - 12 Nov 2024

Abstract

Uranium mineralization related to Na-metasomatism is known as Na-metasomatite or albitite-type. They represent the fourth-largest uranium resource globally and constitute fifty thousand tons of U resources. The present work gives details about well-known Na-metasomatic uranium occurrences worldwide in terms of structures, metasomatic stages, [...] Read more.

Uranium mineralization related to Na-metasomatism is known as Na-metasomatite or albitite-type. They represent the fourth-largest uranium resource globally and constitute fifty thousand tons of U resources. The present work gives details about well-known Na-metasomatic uranium occurrences worldwide in terms of structures, metasomatic stages, geochemical characteristics, fluid inclusions, and compositions of stable isotopes. The host rocks are granite, granitoid, and metamorphosed volcano-sedimentary rocks, and these rocks experienced two/three deformational stages. U mineralization is mainly confined to faults and characterized by granitic intrusive, cataclasis, mylonitization, and albitization. The albitized rocks exhibit two to three metasomatic and late hydrothermal stages. The first stage is marked by the replacement of pre-existing host minerals during a ductile shear regime. The second stage is related to U mineralization contemporaneous with the brittle deformation. The albitized rocks exhibit depletion in Si, K, Ba, and heavy rare-earth elements relative to the host rocks and enrichments in Na, Ca, U, Zr, P, V, Sr, and light rare-earth elements. U-enrichment is positively correlated with Na, Mo, Cu, and high-field strength elements. The pressure–temperature (P-T) conditions of U mineralization are considered to be epithermal and mesothermal. Fluid inclusion studies indicate that the mineralizing fluids were rich in Na⁺, Mg²⁺, Cl⁻, CO₂, H₂O, F⁻, and PO₄³⁻ and meteoric–magmatic derived. The geological processes responsible for the genesis of Na-metasomatic U deposits of the North Delhi Fold Belt (India) are comparable with some international examples, i.e., Australia, Ukraine, Cameroon, Brazil, Guyana, China, and the USA. Full article

(This article belongs to the Section Geochemistry)

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15 pages, 19310 KiB

Open AccessArticle

Kavokta Deposit, Middle Vitim Mountain Country, Russia: Composition and Genesis of Dolomite Type Nephrite

by Evgeniy V. Kislov

Geosciences 2024, 14(11), 303; https://doi.org/10.3390/geosciences14110303 - 10 Nov 2024

Abstract

The Kavokta deposit of the dolomite type nephrite is located in the Middle Vitim mountain country, Russia (Russian Federation). The deposit area is composed of granite of the Late Paleozoic Vitimkan complex. The granite contains complex shape blocks of Lower Proterozoic rocks. They [...] Read more.

The Kavokta deposit of the dolomite type nephrite is located in the Middle Vitim mountain country, Russia (Russian Federation). The deposit area is composed of granite of the Late Paleozoic Vitimkan complex. The granite contains complex shape blocks of Lower Proterozoic rocks. They are represented by metasandstone, crystalline schist, amphibolite, and dolomite marble. The calcite–tremolite and epidote–tremolite skarns were formed on the contact of dolomite and amphibolite. Calcite–tremolite skarn contains nephrite bodies. The mineral composition of 16 core samples obtained during the geological exploration conducted by JSC “Transbaikal Mining Enterprise” within Vein 1 of Prozrachny site has been studied in thin sections using a petrographic microscope, and in polished sections using a scanning electron microscope, with an energy-dispersive microanalysis system. Twenty-five minerals have been identified. They have been attributed to relict, metasomatic associations of the pre-nephrite and nephrite stages and hydrothermal and secondary associations. The intensity of the nephrite’s green color is explained by the Fe admixture in tremolite, and the black color is explained by its transition to actinolite in the areas of contact with epidote–tremolite skarn after amphibolite. In the formation and alteration of nephrite, dolomite is replaced by diopside, diopside by tremolite, prismatic tremolite by tangled fibrous tremolite, and tremolite by chlorite. Granite provides heat for metasomatism. Participation of amphibolite in the nephrite formation determines the variety of nephrite colors. The role of metamorphism is reduced to tectonic fragmentation facilitating fluid penetration; stress provides a tangled fibrous cryptocrystalline texture. Full article

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18 pages, 6076 KiB

Open AccessArticle

Durability of Two-Component Grout in Tunneling Applications: A Laboratory Test Campaign

by Carmine Todaro, Andrea Carigi and Daniele Peila

Geosciences 2024, 14(11), 302; https://doi.org/10.3390/geosciences14110302 - 10 Nov 2024

Abstract

Today, two-component grout is the most widely used backfilling technology in shielded mechanized tunneling. Despite its intensive use, however, very scant information pertaining to the durability of this material is available in the scientific literature. In this work, the aging of two-component grout [...] Read more.

Today, two-component grout is the most widely used backfilling technology in shielded mechanized tunneling. Despite its intensive use, however, very scant information pertaining to the durability of this material is available in the scientific literature. In this work, the aging of two-component grout is studied by curing grout samples using three different modalities. Furthermore, the action of air on two-component grout is studied by assessing the dehydration process, which is a phenomenon that occurs when the material is cured without being completely embedded in soil/rock. Uniaxial compression tests and three-point flexural tests have been carried out for mechanical characterization. The results reveal that in a curing environment made of sand, a moisture of 5% is sufficient to guarantee correct curing of the grout and extend the mechanical performance to three years, whereas the action of air is potentially dangerous, since the grout suffers strongly from dehydration. Despite this dehydration process, however, the mechanical performance of the grout also tends to increase for samples cured under the action of air until a very high level of cracking and shrinkage is reached. A discussion of the limitations on the uniaxial compression strength as the main mechanical parameter for the characterization of two-component grout concludes the work. Full article

(This article belongs to the Section Geomechanics)

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19 pages, 14600 KiB

Open AccessArticle

Non-Linear Effects of Gravity Change on Mantle Dynamics

by Paolo Mancinelli, Giorgio Ranalli and Cristina Pauselli

Geosciences 2024, 14(11), 301; https://doi.org/10.3390/geosciences14110301 - 7 Nov 2024

Abstract

Starting from observed variations of the length of day in the past 2.5 billion years, we calculate the corresponding gravity variation and evaluate the possible effects that such variation would have induced on the lithosphere and on mantle convection. The lithospheric stress induced [...] Read more.

Starting from observed variations of the length of day in the past 2.5 billion years, we calculate the corresponding gravity variation and evaluate the possible effects that such variation would have induced on the lithosphere and on mantle convection. The lithospheric stress induced by the observed gravity increase at the equator in 500 Ma is of the same order as the one associated with a convective cell. We model a gravity increase that would result in 1.3 × 10⁻² µGal or 1.3 × 10⁻¹⁰ m s⁻² over 10 years, a value that is not far from the detection thresholds of modern gravimeters. Gravity increase also affects mantle dynamics by improving convection efficiency. Our models demonstrate that gravity variations contribute to this phenomenon through faster and wider mixing. The results support a view where a convective system being subject to gravity changes responds through non-linear adjustments of its effective mixing at all scales. These findings contribute to a deeper understanding of how gravitational fluctuations may shape the behavior of Earth’s dynamic systems over geological timescales. Full article

(This article belongs to the Special Issue Editorial Board Members’ Collection Series: “New Horizons in Geophysics: From Theory to Applications”)

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23 pages, 7771 KiB

Open AccessArticle

Investigation of the Effect of Integrated Offset, GPS, and InSAR Data in the Stochastic Source Modeling of the 2002 Denali Earthquake

by Parva Shoaeifar and Katsuichiro Goda

Geosciences 2024, 14(11), 300; https://doi.org/10.3390/geosciences14110300 - 6 Nov 2024

Abstract

This study investigates the effect of geological field measurement (offset), global positioning system (GPS), and interferometric synthetic aperture radar (InSAR) data on the estimation of the co-seismic earthquake displacements of the 2002 Denali earthquake. The analysis is conducted using stochastic source modeling. Uncertainties [...] Read more.

This study investigates the effect of geological field measurement (offset), global positioning system (GPS), and interferometric synthetic aperture radar (InSAR) data on the estimation of the co-seismic earthquake displacements of the 2002 Denali earthquake. The analysis is conducted using stochastic source modeling. Uncertainties associated with each dataset limit their effectiveness in source model selection and raise questions about the adequate number of datasets and their type for reliable source estimation. To address these questions, stochastic source models with heterogeneous earthquake slip distributions are synthesized using the von Kármán wavenumber spectrum and statistical scaling relationships. The surface displacements of the generated stochastic sources are obtained using the Okada method. The surface displacements are compared with the available datasets (i.e., offset, GPS, and InSAR) individually and in an integrated form. The results indicate that the performance of stochastic source generation can be significantly improved in the case of using GPS data and in the integrated case. Overall, based on the case study of the 2002 Denali earthquake, the combined use of all available datasets increases the robustness of the stochastic source modeling method in characterizing surface displacement. However, GPS data contribute more than InSAR and offset data in producing reliable source models. Full article

(This article belongs to the Special Issue New Trends in Earthquake Engineering and Seismotectonics)

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16 pages, 42046 KiB

Open AccessArticle

Characterisation of Fault-Related Mn-Fe Striae on the Timpa Della Manca Fault (Mercure Basin, Southern Apennines, Italy)

by Sabrina Nazzareni, Luciana Mantovani, Mattia Pizzati, Danilo Bersani, Tiziano Boschetti, Ambra Palmucci, Daniele Cirillo and Francesco Brozzetti

Geosciences 2024, 14(11), 299; https://doi.org/10.3390/geosciences14110299 - 5 Nov 2024

Abstract

The Quaternary Mercure basin is a complex fault structure located in the Pollino region of the southern Apennines (Italy). A persistent seismic gap makes the Mercure basin structure one of Italy’s highest seismic risk zones. The southernmost termination of the Mercure basin is [...] Read more.

The Quaternary Mercure basin is a complex fault structure located in the Pollino region of the southern Apennines (Italy). A persistent seismic gap makes the Mercure basin structure one of Italy’s highest seismic risk zones. The southernmost termination of the Mercure basin is the Timpa della Manca fault. The fault’s mirror is characterised by distinctive, lineated, black-coloured striae decorating a cataclasite made of carbonate clasts. These black-coloured striae consist of a mixture of Mn phases, including hollandite, todorokite, birnessite, and orientite, which are associated with goethite and hematite along with minor amounts of phyllosilicates (chlorite, muscovite), quartz, and sursassite. This mineral association and their phase stability suggest that hydrothermal circulating fluids may have mobilised and re-precipitated low-temperature Mn hydrous phases within the shear zone, leaving remnants of higher-temperature minerals. Oceanic crust remnant blocks within the Frido Unit appear to be the most likely source of the Mn. The uniqueness of the Mn striae on the Timpa della Manca fault offers intriguing insights into fluid circulation within the Mercure basin tectonic system, with potential implications for the seismotectonic characteristics of the Pollino region. Full article

(This article belongs to the Special Issue The Tectonic Origins of Sedimentary Basins: Provenance and Evolution Across Geological Time)

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20 pages, 25703 KiB

Open AccessArticle

The Subduction-Related Metavolcanic Rocks of Maroua, Northern Cameroon: New Insights into a Neoproterozoic Continental Arc Along the Northern Margin of the Central African Fold Belt

by Pierre Christel Biakan à Nyotok, Merlin Gountié Dedzo, Diddi Hamadjoda Djamilatou, Nils Lenhardt, Moussa Ngarena Klamadji, Periclex Martial Fosso Tchunte and Pierre Kamgang

Geosciences 2024, 14(11), 298; https://doi.org/10.3390/geosciences14110298 - 5 Nov 2024

Abstract

The metavolcanic rocks around Maroua in the Far North Region of Cameroon are located at the northern margin of the Central African Fold Belt (CAFB) and have not been studied to date. The petrographic and whole-rock geochemical data presented in this paper highlight [...] Read more.

The metavolcanic rocks around Maroua in the Far North Region of Cameroon are located at the northern margin of the Central African Fold Belt (CAFB) and have not been studied to date. The petrographic and whole-rock geochemical data presented in this paper highlight their magma genesis and geodynamic evolution. The lavas are characterized by basaltic, andesitic, and dacitic compositions and belong to the calc-alkaline medium-K and low-K tholeiite series. The mafic samples are essentially magnesian, while the felsic samples are ferroan. On a chondrite-normalized REE diagram, mafic and felsic rocks display fractionated patterns, with light REE enrichment and heavy REE depletion (La_N/Yb_N = 1.41–5.38). The felsic samples display a negative Eu anomaly (Eu/Eu* = 0.59–0.87), while the mafic lavas are characterized by a positive Eu anomaly (Eu/Eu* = 1.03–1.35) or an absence thereof. On a primitive mantle-normalized trace element diagram, the majority of the samples exhibit negative Ti and Nb–Ta anomalies (0.08–0.9 and 0.54–0.74, respectively). These characteristic features exhibited by the metavolcanic rocks of Maroua are similar to those of subduction-zone melts. This subduction would have taken place after the convergence between the Congo craton (Adamawa-Yadé domain) and the Saharan craton (Western Cameroonian domain). Petrological modelling using major and trace elements suggests a derivation of the Maroua volcanics from primitive parental melts generated by the 5–10% partial melting of a source containing garnet peridotite, probably generated during the interaction between the subducted continental crust and the lithospheric mantle and evolved chemically through fractional crystallization and assimilation. Full article

(This article belongs to the Section Geochemistry)

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22 pages, 15680 KiB

Open AccessArticle

Three-Dimensional Subsurface Model of Luk-Ulo Melange Complex, Karangsambung, Indonesia: Insights from Gravity Modeling

by Faridz Nizar Ahmady, Djoko Santoso, Susanti Alawiyah and Asep Saepuloh

Geosciences 2024, 14(11), 297; https://doi.org/10.3390/geosciences14110297 - 5 Nov 2024

Abstract

The Luk-Ulo Melange Complex (LMC) is characterized by a chaotic assemblage of mixed rocks with a block-in-matrix fabric. The exposed blocks consist of various scattered rock types, trending in an ENE-WSW direction. In the case of Mt. Parang, the origin of the diabase [...] Read more.

The Luk-Ulo Melange Complex (LMC) is characterized by a chaotic assemblage of mixed rocks with a block-in-matrix fabric. The exposed blocks consist of various scattered rock types, trending in an ENE-WSW direction. In the case of Mt. Parang, the origin of the diabase remains uncertain, with ongoing debate as to whether it is associated with in situ volcanic activity or represents an exotic block within the melange deposit. Subsurface data obtained through geophysical investigation can aid in modeling the geometry of intrusive bodies using inverse modeling techniques. In this study, we conducted a gravity survey and performed 3D inverse modeling to investigate the subsurface beneath Karangsambung. A total of 818 gravity data points and 28 rock density measurements were integrated with existing geological data to construct an a priori 3D geological model. To ensure the results align with geological concepts, the 3D inversion utilized a stochastic approach, allowing for the incorporation of multiple geological constraints over fifty million iterative procedures. Ultimately, the inversion successfully reduced the misfit between observed and calculated data from 2.71 to 0.55 mGal. Based on the inverted 3D model, the diabase rock in Mt. Parang is identified as having an intrusive origin. The intrusion model exhibited minimal changes in density, volume, and shape during the inversion process. Additionally, the model suggests the presence of a solidified magma reservoir at a depth of approximately 3 km, potentially related to Dakah volcanism. The inverted model also reveals the block-in-matrix structure of the Luk-Ulo Melange Complex in the northern area. Full article

(This article belongs to the Section Geophysics)

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18 pages, 4842 KiB

Open AccessArticle

Natural H₂ Transfer in Soil: Insights from Soil Gas Measurements at Varying Depths

by Cesar Patino, Dora Piedrahita, Elkin Colorado, Katherine Aristizabal and Isabelle Moretti

Geosciences 2024, 14(11), 296; https://doi.org/10.3390/geosciences14110296 - 4 Nov 2024

Abstract

The exploration of natural H₂ is beginning in several countries. One of the most widely used methods for detecting promising areas is to measure the H₂ percentage of the air contained in soils. All data show temporal and spatial variabilities. The [...] Read more.

The exploration of natural H₂ is beginning in several countries. One of the most widely used methods for detecting promising areas is to measure the H₂ percentage of the air contained in soils. All data show temporal and spatial variabilities. The gradient versus depth is not usually measured since the standard procedure is to drill and quickly install a tube in the soil to pump out the air. Drill bits used do not exceed one meter in length. These limitations have been overcome thanks to the development of a new tool that enables percussion drilling and gas measurements to be carried out with the same tool until 21 feet deep. This article shows the results obtained with this method in the foreland of the Colombian Andes. The variation of the gradient as a function of depth provides a better understanding of H₂ leakage in soils. Contrary to widespread belief, this gradient is also highly variable, and, therefore, often negative. The signal is compatible with random and discontinuous H₂ bubbles rising, but not with a permanent diffusive flow. Near-surface bacterial consumption should result in a H₂ increase with depth; it may be true for the first tens of centimeters, but it is not observed between 1 and 5 m. The results show that, at least in this basin, it is not necessary to measure the H₂ content at depths greater than the conventional one-meter depth to obtain a higher signal. However, the distance between the measured H₂ peaks versus depth may provide information about the H₂ leakage characteristics and, therefore, help quantify the near-surface H₂ flow. Full article

(This article belongs to the Section Geomechanics)

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14 pages, 5194 KiB

Open AccessArticle

Machine Learning Insights into the Last 400 Years of Etna Lateral Eruptions from Historical Volcanological Data

by Arianna Beatrice Malaguti, Claudia Corradino, Alessandro La Spina, Stefano Branca and Ciro Del Negro

Geosciences 2024, 14(11), 295; https://doi.org/10.3390/geosciences14110295 - 3 Nov 2024

Abstract

Volcanic hazard assessment is generally based on past eruptive behavior, assuming that previous activity is representative of future activity. Hazard assessment can be supported by Artificial Intelligence (AI) techniques, such as machine learning, which are used for data exploration to identify features of [...] Read more.

Volcanic hazard assessment is generally based on past eruptive behavior, assuming that previous activity is representative of future activity. Hazard assessment can be supported by Artificial Intelligence (AI) techniques, such as machine learning, which are used for data exploration to identify features of interest in the data. Here, we applied a machine learning technique to automate the analysis of these datasets, handling intricate patterns that are not easily captured by explicit commands. Using the k-means clustering algorithm, we classified effusive eruptions of Mount Etna over the past 400 years based on key parameters, including lava volume, Mean Output Rate (MOR), and eruption duration. Our analysis identified six distinct eruption clusters, each characterized by unique eruption dynamics. Furthermore, spatial analysis revealed significant sectoral variations in eruption activity across Etna’s flanks. These findings, derived through unsupervised learning, offer new insights into Etna’s eruptive behavior and contribute to the development of hazard maps that are essential for long-term spatial planning and risk mitigation. Full article

(This article belongs to the Section Natural Hazards)

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