Structural Uplift Research Articles

A hypothesis of the obliquely subducted Gagua Ridge below Nanao Basin based on uplifted structures in Ryukyu forearc

At the southernmost part of the Ryukyu subduction zone, six long-offset multi-channel seismic profiles were collected across three forearc basins and the southern Ryukyu accretionary prism during the TAIGER experiment in 2009 and the TAICRUST project in 1995. These profiles were reprocessed to generate pre-stack depth migration (PSDM) sections. In addition, two velocity-interface models were obtained by reanalyzing active source data recorded from 28 ocean-bottom seismometers during the same TAIGER experiment, in consideration of the PSDM sections and previous tomography models. Due to the northwest convergence of the Philippine Sea Plate (PSP), it is suggested that the Gagua Ridge may have been obliquely subducting northwestward beneath the Ryukyu prism and below the Nanao Basin. The PSDM sections and the velocity-interface models indicate the subducted Gagua Ridge causing the uplift of the sedimentary basement and the lower crustal structure below the Nanao Basin. The sedimentary and crustal structures near ~ 122.5° E beneath the Nanao Basin were also uplifted where shallow earthquakes had occurred by the oblique subduction of the Gagua Ridge depicted in the isopach map of the crust. Furthermore, a recent earthquake (Mw ~ 6.0) occurred near the northeast coast of Taiwan in 2018 at a depth of approximately 12 km below the Hsincheng Ridge. Our study suggests that this earthquake was caused by a thrust fault near the décollement, which might have been formed by the subduction of the PSP.

Facies framework and depositional setting of the Middle-Upper Eocene Hamra Formation, north of Bahariya Oasis, Western Desert, Egypt

The Middle-Upper Eocene Hamra Formation, covering the northern plateau of the Bahariya Oasis, northwestern Desert, comprises two informal (lower and upper) members; the lower member (Upper Middle Eocene, 34.5-m thick) is made up entirely of fossiliferous limestone rocks (Nummulites gizehensis, Nummulites champolioni), while the upper member (Late Eocene, 38-m thick) consists of an intercalation of limestone with thin beds of sandstone, siltstone, and claystone. The upper member is highly fossiliferous with Turrittella, Carolia palcnoids, and Ostrea multicostata. Seven carbonate and three clastic microfacies have been recognized in five measured sections of the Hamra Formation. The carbonate microfacies were deposited on the proximal ramp setting of a warm and shallow sub-tropical environment. The lower member can be correlated with the (Upper Middle Eocene) Sath El Hadid and Fashn formations, while the upper member is correlated with the Upper Eocene Beni Sueif Formation. The reduced thickness of both members of the Hamra Formation compared with the corresponding rock units to the east reflects the structural uplift prevailed in the north of Bahariya Oasis during sedimentation.

Assessment of the deep oil and gas bearing potential onshore in the west of Azerbaijan (Tarsdallar area)


 
 
 The Tarsdeller oil and gas field, which has a brachyoanthicline structure, is the most promising area of the oil-gas region (OGR) in the Kura-Gabirri interfluve. Goal: Based on the reservoir characteristics of rock samples obtained from exploration wells drilled in the area adjacent to the field, petrophysical models have been compiled, reflecting the spatial variation in porosity and permeability of oil-containing reservoirs. Objects: Consideration of the petrophysical properties of core samples taken in the study area made it possible to confirm the oil and gas potential of deep-seated reservoirs. Methods: This analyzed the values and variation of petrophysical properties by depth, age and various physical factors. The observed wide range of changes in the reservoir properties of rocks in the study area is mainly due to tectonic changes, lithological heterogeneity of the sedimentary complex, differences in the depth of bedrocks, as well as the complexity of tectonic conditions. As a result, to predict the oil and gas content in deep reservoirs of the same structures, it is advisable to use the methods of exploration geophysics, as well as the results of changes inthe reservoir characteristics of rocks, determined by petrophysical data. At the same time, it is most expedient to focus on the study of Paleogene-Cretaceous tectonics for the search for oil and gas objects using prospecting and exploration (preferably aerial-photo-space) works at the field. Results: Models made in 3D format illustrate the predicted oil and gas potential and patterns of distribution of productive horizons involved in the geological structure of oil and gas deposits, along the depths and stratigraphic units. It is shown that although the permeability of the rocks in the area is low, the porosity values are favorable for the industrial accumulation of hydro-carbons. Fractured carbonate reservoirs of the Upper Cretaceous are the most promising among the Mesozoic sediments in the OGRbetween the Kura and Gabirri rivers. Deep-seated structural uplifts complicated by large-amplitude fractures are recommended as the priority targets for further geological exploration. However, the real potential of the Eocene deposits, which are widespread in the NGR between the Kura and Gabirri rivers, remains unexplored by deep drilling. This is due, on the one hand, to the incomplete opening of the Eocene section in the structures prepared for deep drilling, structural-tectonic and lithofacies features, as well as insufficient knowledge of drilling for oil and gas, and on the other hand, poor development of promising intervals of the section.
 
 

The Occurrence of Recent-Subrecent Seabed Acoustic Anomalies and Its Relationship with Structural Uplift around the Waipoga Trough, West Papua-Indonesia

Marine Geological Institute acquired high-resolution seismic and acoustic data during a survey in the Waipoga Trough-West Papua in 2018. The profiles show acoustically blanking, turbid, and cloudy occur along the trough floor over 3,000 km2. Many accoustic chimneys are breaking through the seabed of recent and subrecent sediment layers. It is suggested due to the local expulsion of methane gas. The pockmarks occur as transparent and turbid acoustic characteristics. They locally have relief down to 2-10 m below the seafloor with horizontal dimensions up to 25 -100 m in width. Methane formation due to the rapid deposition of organic-rich sediment down the uplifted area around the trough, associated with thrust fold tectonics is suggested as a triggering agent for the acoustic anomaly formation.

Tectono-stratigraphic framework and evolution of East Junggar Basin, Central Asia

The late Paleozoic development of the East Junggar Basin and adjoining mountain belts was critical to the construction of the larger Central Asian Orogenic System, yet the structural framework of basement rocks and overlying strata of the basin and their spatio-temporal relationship with adjacent thrust-bounded ranges remain poorly constrained. In this study, we conducted reflection seismology and compiled existing geologic observations of the East Junggar Basin and adjacent Bogda Shan to the south and Kelameili Shan to the north to construct cross sections depicting the tectono-stratigraphic framework and evolution of the region. Our work shows that Carboniferous–Permian strata overlying basement rocks in the East Junggar Basin occur in structural uplifts and depressions and feature at least five major unconformities. The structure of the East Junggar Basin is characterized by: (1) horsts and grabens involving basement rocks and overlying Carboniferous–Jurassic strata; (2) series of stratigraphic depressions marked by Jurassic–Cretaceous strata; and (3) a south-dipping monocline in uppermost Neogene–Quaternary strata. Mesozoic–Cenozoic strata are absent along the northern margin of the East Junggar Basin at the Kelameili Shan. Strata are generally older from the Kelameili Shan to the northern East Junggar Basin where Devonian–Carboniferous strata are thrust southward over younger strata. In contrast, thicker sequences of Cretaceous–Quaternary strata are present in the southern portion of the East Junggar Basin. Strata of the East Junggar Basin were deposited in a foreland depression formed in the footwall of a leading, north-directed thrust of the Bogda Shan. The overall tectono-stratigraphic framework of the East Junggar Basin is a product of tectonic activity varying in time and space along the northern and southern basin-mountain interfaces since the late Paleozoic.

High-resolution magnetochronology detects multiple stages of Pleistocene tectonic uplift and deformation in the Po Plain of northern Italy

AbstractWe developed a high-resolution magnetochronology of the Pleistocene stratigraphy of the Monte Netto hillock, a tectonically uplifted structure in the Po Plain of northern Italy. Our data allowed reconstructing the depositional age of the sequence and assessing rates of deformation and rock uplift of the neotectonic structure, thus providing constraints on the tectono-sedimentary evolution of this seismically active part of the buried Southern Alps. Using a combination of magnetostratigraphy and paleosecular variation analysis, we generated an age-depth model for the Monte Netto stratigraphy that encompasses, from the top, Upper Pleistocene (11–72 ka) loess-paleosols overlaying fluvial sediments spanning the Brunhes-Matuyama boundary (773 ka) and the top of the Jaramillo (990 ka). The identification of the same magneto-chronostratigraphic surfaces in nearby drill cores from regions of the Po Plain that have not been affected by neotectonic deformation allowed estimating a mean rate of tectonic uplift of the hillock relative to the neighboring plain of 11.3 ± 1.5 cm/ka, and an absolute uplift relative to sea level of ~19.3 cm/ka. Finally, our paleomagnetic analyses from the uppermost loess sequence disclosed the complexity of the tectonic evolution of the Monte Netto structure, which shows evidence of a two-phase rotational deformation linked to coseismic surface faulting due to recent seismic activity.

Distribution characteristics and controlling factors of helium-rich gas reservoirs

With the increasing demand for helium and the gradual shortage of proven helium resources, discussing the distribution characteristics and controlling factors of helium-rich reservoirs discovered around the world can not only help us deeply understand the accumulation process of helium in the crust, but also provide guidance for finding helium resources. Based on the compilation of gas chemical composition, stable isotope and noble gas isotope data of helium-rich gas reservoirs found in the world, this paper discusses the distribution characteristics and key controlling factors in combination with geological data. According to the chemical composition, helium-rich gas reservoirs can be divided into three types: helium-rich CH4, helium-rich CO2 and helium-rich N2. Among them, helium-rich CH4 reservoirs are mainly distributed in cratons, while helium-rich CO2 and helium-rich N2 reservoirs are distributed in orogen and fault zones. The gas-producing layers of different types of helium-rich gas reservoirs almost show the characteristics of ancient age and shallow burial. The helium reserves of helium-rich CH4 and helium-rich CO2 reservoirs are similar and significantly larger than those of helium-rich N2 reservoirs, but the helium content shows the opposite characteristics. Helium source, supplying intensity of associated gas, helium accumulation mode, and tectonic-magmatic activity may be the key factors controlling the distribution of helium-rich gas reservoirs in the crust. As far as helium exploration is concerned, the Proterozoic and Paleozoic traps located in uplift structure which has developed Precambrian granite basement, moderate distance from the gas supply center, high geothermal gradient and developed faults are the most effective exploration target. At the same time, the Meso-Cenozoic traps connecting with the Precambrian granite basement through unconformity or deep-seated faults can also be used as potential exploration targets for helium resources.

Identifying the optimal intensity measure and key factors of earthquake liquefaction-induced uplift of underground structures

Identifying the optimal intensity measure and key factors of earthquake liquefaction-induced uplift of underground structures

Quantification of Impact‐Induced Melt Production in Numerical Modeling Revisited

AbstractMelting and vaporization of rocks in impact cratering is mostly attributed to be a consequence of shock compression. However, other mechanism such as plastic work and decompression by structural uplift also contribute to melt production. In this study we expand the commonly used method to determine shock‐induced melting in numerical models from the peak shock pressure by a new approach to account for additional heating due plastic work and internal friction. We compare our new approach with the straight‐forward method to simply quantify melting from the temperature relative to the solidus temperature at any arbitrary point in time in the course of crater formation. This much simpler method does account for plastic work but suffers from reduced accuracy due to numerical diffusion inherent to ongoing advection in impact crater formation models. We demonstrate that our new approach is more accurate than previous methods in particular for quantitative determination of impact melt distribution in final crater structures. In addition, we assess the contribution of plastic work to the overall melt volume and find, that melting is dominated by plastic work for impacts at velocities smaller than 7.5–12.5 km/s in rocks, depending on the material strength. At higher impact velocities shock compression is the dominating mechanism for melting. Here, the conventional peak shock pressure method provides similar results compared with our new model. Our method serves as a powerful tool to accurately determine impact‐induced heating in particular at relatively low‐velocity impacts.

Facies partitioning of fluvial, wave, and tidal influences across the shoreline-to-shelf architecture in the Western Interior Campanian Seaway, USA

Abstract The influence of bottom currents and tectonic activity on shelf sedimentary processes and sand distribution remains poorly constrained. A growing body of research highlights the importance and variability of the shelf sandstone bodies. To explore the roles of fluvial, wave and bottom current-controlled sediment distribution in the Western Interior Seaway, 21 marine sandstone outcrops in Wyoming and Colorado were analysed. Recurring facies associations include: paralic, tide-influenced coastal margins; mainly east and SE prograding, wave-dominated delta-fronts and shorefaces; heavily bioturbated, glauconitic sandstones; and traction current-dominated, tidally influenced, open-marine subaqueous delta and shelf deposits, with southward palaeocurrent directions. Intense reworking by a moderately diverse ichnofauna occurs in wave-dominated and glauconitic facies. Minimal burrowing occurs in cross-stratified subaqueous delta and shelf deposits. Lithofacies associations are interpreted to change basinward with increasing water depth. Ichnoassociations reflect the proximity of river mouths. Widespread, southward palaeocurrent directions, not restricted to a narrow longshore zone, on the shallow-marine shelf indicate the persistence of strong, along-shelf sand-transport which has not been previously documented in detail. Palaeobathymetric complexity caused by uplift of Laramide structures amplified and accelerated bottom and tidal currents and facilitated the erosion, transport and deposition of older sediments.

Learner Milestones to Guide Decolonial Global Health Education.

The current movement to 'decolonize' global health aims to both dismantle colonial frameworks that perpetuate inequity and racism, as well as to rebuild and uplift structures and systems that celebrate indigeneity. However, it is critical to recognize that teaching decoloniality within global health education is more than just the acknowledgement that there are key paradigms missing from current global health education. It is imperative to have a methodology to hold ourselves and our learners accountable to progress in practices and ideals that promote equity-based praxis. In this paper, we propose the creation of a tool to assess learner levels and their progression over time in both recognizing the impacts of colonialism and acting to transform their own global health praxis towards equity and decoloniality. We developed a model to illustrate an increasing scope and impact of decolonial and global health equity praxis. We hypothesize through this model that the way in which learners engage with power dynamics and structural advocacy at each level is essential to describing learner stages. Based on extensive literature review, existing curricular frameworks, global partner discussion(s), feedback on our pilot curriculum, and adaptation of philosophical theory, these learner milestones were conceptualized. We discuss the inherent challenges in assessment of the complex mix of knowledge, attitude and skills described in these milestones with the understanding that any such assessment would always be formative, as we all continue learning how to do better. We hope these milestones can be utilized to promote critical transformational change in the field of global health. This requires deep self-reflection and examination of existing structures of oppression followed by intentional reparative actions to embody decoloniality in our praxis and advocacy and reimagine global health based on equity and local leadership.

Model test and numerical simulation on the invert heave behaviour of high-speed railway tunnels with rainstorm

Extreme weather with torrential rainstorms has brought a new challenge to the operation of railway tunnels in karst areas. Especially for high-speed railway (HSR) tunnels, the uplift of the invert structure caused by the high external water pressure (EWP) seriously affects the normal operation of the HSR line. This paper presented a series of 3D printing model tests to investigate the occurrence mechanism and evolution law of invert heave disease after rainstorm and drainage blockage. Numerical simulations were used to study the mechanical response of the tunnel structure under different groundwater levels and drainage blockage degrees. The results show that the uplift displacement of the invert increases with the EWP. The maximum EWP occurs at the invert whether the drainage system is blocked or not, which is the main factor leading to such disease. Drainage blockages increase the severity of the disease. Especially with blockages exceeding 50%, the EWP on the invert and the corresponding uplift displacement increase significantly. Furthermore, groundwater levels and drainage blockages will both cause increased stresses in the tunnel bottom structure, leading to problems such as excessive uplift displacement and cracking. Some useful suggestions for tunnel construction and operation were obtained from the results.

Characterization of Structural Geology of Faihaa Oilfield, Southern Iraq

Faihaa Oilfield is a new exploration Iraqi Oilfield located in southern Iraq and within Mesopotamian Plain, including the Block 9 exploration area, along the Iraqi-Iranian border. The study area included Faihaa Oilfield (in Iraq) and Yadavaran Oilfield (in Iran). They belong to one anticline (Dome) structure separated by the Iraqi-Iranian border, without a geological boundary between the fields. The current study aims to achieve structural geology analysis to the study area (Faihaa/Yadavaran structure). The structural analysis included geometric and genetic analyses of the study area. According to geometric and genetic analyses results, the Faihaa/Yadavaran structure is classified as an anticline, gentle, upright, non-plunge, and asymmetrical. According to thickness variation, there are two types of formations’ folds are recognized, Thickened and Supratenuous fold generated by two folding mechanisms bending and buckle mechanisms. Bending form Supratenuous fold, perhaps due to the vertical uplift of salt structure and/or basement faults, while buckle produces Thickened fold because of the parallel tectonic movement causes collision between Arabian Plate and Eurasian Plate. Consequently, a special strain pattern was formed and the reservoir quality in the crest of Mishrif and Yamama Formations was the best. The fold axis of the Faihaa/Yadavaran structure has a Boomerang shape, whereas it is almost straight from south to the center of the structure, then tends to the NW with different deviations over the study area formations. This direction may be due to the anticlockwise rotation of the Arabian Plate motion. The results of geometric and genetic analyses revealed that may be Faihaa/Yadavaran structure is one structural trap formed by tectonic activities; Hormuz salt structures, reactivated Basement faults, and Collision between Arabian and Eurasian Plates. The intensity of the tectonic activities of the study area maybe be less than surrounding Oilfields, therefore, the Faihaa Oilfield formation's depth was deeper than adjacent Oilfields.

Analysis of Regional and Residual Gravity Disturbance of Major Fault Belts in the Tarim Basin, Western China

Large fault belts often influence the paleo-geomorphic changes in basins and control hydrocarbon accumulation and distribution in basins. Based on the gravity field model European Improved Gravity model of the Earth via New techniques (EIGEN)-6C4, this study calculated the residual Bouguer gravity disturbance of the Tarim Basin by using the minimum curvature method and analyzed gravitational characteristics of major fault belts of the Tarim Basin. The residual Bouguer disturbance exhibits linear residual Bouguer disturbance zones in the Tianshan Mountains, West Kunlun, and the Altyn region, which is consistent with the spatial distribution of their related fault belts. The regional Bouguer disturbance is related to crust–mantle boundary depth, which can be used to roughly estimate crust thickness. Thus, we suggest that the crust–mantle boundary depth order of major faults from deep to shallow is the Altyn region, West Kunlun, and Tianshan Mountains. There is a discontinuity in the residual Bouguer disturbance of West Kunlun, which compares well with the fault belt of West Kunlun. Furthermore, the residual Bouguer disturbance of the Tarim Basin has a series of elliptical areas with a central positive disturbance located within the Bachu uplift and other uplift structures. The residual Bouguer disturbance also reflects the position and distribution of the major fault belts and the boundary of the Tarim Basin, which can provide guidance for dynamic evolution analysis of large basins.

Customary Rights and Freshwater Ecology in Pluralistic Societies on the Monsoonal Island of Sumba (Eastern Indonesia)

This article evaluates the ways water is made and unmade on Sumba Island when subjected to tensions between Indigenous and off-island political ecologies. Located in the eastern Indian Ocean, Sumba has a semi-arid, monsoonal climate with an uplifted coral reef geological structure where a spatially and temporally dynamic hydrological system shapes people’s access to freshwater. Customary adat societies on the island have histories of struggling to maintain the integrity of their own political ecologies, further increasing the precarity of their access to freshwater. The topic of the research reported on in this paper was determined through collaboration with members of the Kodi community in western Sumba who urged the author to study the problem of water. This article highlights ongoing threats to the further degradation of local societies’ rights to control their customary territories and freshwater within them by summarizing the phenomena of water grabbing in Indonesia. Zooming in on three projects that manifest as water grabs, this article finds, respectively, that water grabbing occurs under the guise of forest protection and production, behind the veil of philanthropy, and for economic development with military backing. In all three cases, water grabs take place in the context of a decentralizing nation-state where the ways adat is understood and the ways laws regarding it have been interpreted and enacted have changed through time and have varied between communities, partly in relation to the societies’ proximity to centers of colonial and postcolonial power as well as the development of activities in their territories. On Sumba the content of adat and relationships among distinct adat societies evolves on a bioculturally diverse island that is home to numerous Indigenous ethnolinguistic communities. Consequently, people’s responses to interventions into their political ecologies vary. More broadly, the context for this study is the intersections of water grabbing and social change during the Reformasi, the post-Suharto era of decentralization in Indonesia.

Normal Pressure Shale Gas Preservation Conditions in the Transition Zone of the Southeast Basin Margin of Sichuan Basin

Shale in the Wufeng Formation of the upper Ordovician and Longmaxi Formation of lower Silurian in the Sichuan Basin and its surrounding area is widespread. Shale gas resources are abundant. Shale gas in the Wufeng Formation and the Longmaxi Formation in the basin has been a major breakthrough. The basin margin transition zone in southeastern Chongqing is in an intense tectonic activity area, which is more complicated and special than the stable stratum in the basin. Therefore, it is necessary to put forward higher requirements for preservation conditions and enrichment pattern evaluation of shale gas. Therefore, in view of the complicated structural pattern of the basin margin transition zone in southeastern Chongqing, the preservation conditions and reservoir forming patterns are analyzed through structural evolution, uplift and denudation, fault development, structural styles, roof and floor conditions, and formation pressure. The results show that the main reason for the formation of normal pressure is the late uplift, denudation and fault development. The pressure coefficient from the basin to the outer layer is changed from overpressure to normal pressure, and structural transformation forms the preservation form of shale gas with narrow and steep residual anticline, wide residual syncline and residual slope. The preservation condition evaluation of normal shale gas should be based on structural factors such as structural evolution, structural style, uplift and denudation degree and fault development degree, with formation pressure coefficient as reference condition, combined with material basic conditions such as roof and floor conditions and formation thickness. The findings of this study can help for better understanding of the “sweet spot” prediction of normal pressure shale gas in complex structural area.

Application of hydrochemical and isotopic data to determine the origin and circulation conditions of karst groundwater in an alpine and gorge region in the Qinghai–Xizang Plateau: a case study of Genie Mountain

Complex structural systems, lithological differences, and extreme heterogeneity of aquifers combine to create a complex karst aquifer structure in alpine and gorge areas; however, because of the topography, direct investigation of aquifer structure is difficult. In this study, field survey, hydrochemical, and isotopic data are analyzed to reveal the development of karst groundwater and to describe the karst water cycle in Genie Mountain, Qinghai–Xizang Plateau. The results show that groundwater circulation is mainly controlled by active fracture. Atmospheric precipitation and melting ice and snow are the groundwater recharge sources, and recharge areas are mostly located in high mountains above 4500 m a.s.l. The direction of groundwater flow is mostly controlled by the Jinshajiang active Fault, with drainage areas at the intersection of multiple faults. There are two regional karst water runoff conduits. One is along the Edexi-Hongjunshan Fault, where groundwater runs from south to north; the other is along Gangtonglong Fault, where groundwater runs from north to south, and is discharged at Gangtonglong gully. The groundwater cycle can be divided into three levels: epikarst water circulation; mid to deep karst water circulation; and deep geothermal water circulation. The karst springs located in the outlet of the Huolong gully contain markedly higher levels of Na+ and SO42− than other karst springs because of the leaching effect of groundwater on mirabilite. The presence of evaporites in Huolong gully indicates that the plateau planation formed by the structural uplift will change the local climatic conditions, and then affect the groundwater circulation process and the water–rock reaction in the process.

Impact and habitability scenarios for early Mars revisited based on a 4.45-Ga shocked zircon in regolith breccia

After formation of a primordial crust, early impacts influenced when habitable conditions may have occurred on Mars. Martian meteorite Northwest Africa (NWA) 7034 is a regolith breccia that contains remnants of the earliest Martian crust. The paucity of shock deformation in NWA 7034 was previously cited as recording a decline in giant impacts by 4.48 billion years and evidence for habitable Mars by 4.2 billion years ago. We present new evidence of high-pressure shock effects in a 4.45–billion year–old zircon from the matrix of NWA 7034. The zircon contains {112} shock twins formed in the central uplift of a complex impact structure after 4.45 billion years and records impact pressures of 20 to 30 gigapascals. The zircon represents the highest shock level reported in NWA 7034 and paired rocks and provides direct physical evidence of large impacts, some potentially life-affecting, that persisted on Mars after 4.48 billion years.

Forward modeling of magnetotellurics using Comsol Multiphysics

Magnetotellurics is an electromagnetic geophysical method that has been widely used to study structures in Earth's subsurface. Numerical modeling of magnetotellurics is important for survey design, inversion, geological interpretation and many other aspects of geophysical studies. For example, modeling a subsurface conductive body in terms of its conductivity, geometry and dipping angle would yield substantial information on the phase response and sensitivity in an MT survey. While there are many different modeling techniques, the finite element method is most commonly used. In this effort, we present magnetotelluric models of layered Earth, uplift structures, auroral electrojets, and geomagnetically induced currents in power-line skywires using the commercial finite-element package Comsol Multiphysics. The AC/DC module in Comsol can be used to solve Maxwell's equations in the quasi-static limit for modeling the magnetotelluric response. One of the advantages of Comsol modeling is its Graphical User Interface (GUI), which allows users to solve complex single or multi-physics problems in a meshed domain. The use of Comsol also reduces the need for sophisticated computer coding when solving partial differential equations such as Maxwell's equations. In the effort presented here, we first discuss model validation for layered Earth geometries. We then present two examples of magnetotellurics modeling in impact crater and geomagnetically induced current studies. Numerical results were compared with analytical solutions or benchmark results whenever possible.

Hydrocarbon generation characteristics of source rocks of Kong-2 Member in Weibei Sag and its control on the distribution of oil and gas

Small and complex petroliferous sags have gradually become one of the key areas of succession in the mature exploration areas. Taking Weibei Sag of Bohai Bay Basin as a case, the geological and geochemical characteristics of the source rocks of Kong-2 Member was analyzed, the basin simulation method was used to determine the main hydrocarbon generation area, and investigate its control on the distribution and enrichment of hydrocarbon. The results show that the abundance, type, and maturity of organic matter have a large spatial variation range, and the upper and middle sub-members of Kong-2 Member in the study area are the most important source rocks. The periods of the late deposition of the Sha-4 Member and the structural uplift are the main hydrocarbon generation periods. The Migration of hydrocarbon-generating center from subsidence center to southeast direction, resulting a large amount of hydrocarbon-generating in the slope zone, leading to the main migration and accumulation direction of hydrocarbon in the Zaohu Faulted Nose Belt. Therefore, the hydrocarbon were enriched in the southeast and poor in the central and western regions, so the next favorable exploration areas include Zaohu Faulted Nose Belt, Eastern Wacheng Step Belt, and Southern Northern Sag Belt.