Gravity Anomaly Research Papers - Academia.edu (original) (raw)

2025, Scientific_Reports

The reservoir characterization of the Yolde Formation was conducted to assess the hydrocarbon potential of the Kolmani field in the Gongola Basin, Upper Benue Trough. This evaluation utilized Pressure, Temperature, PVT, mobility, and well log data. Data from repeated formation testers (RFT), modular formation testers (MDT), PVT laboratory results, and well logs were analyzed to achieve a comprehensive understanding of the Yolde Formation reservoir. The pressure data and PVT analysis revealed the presence of gas and water in the Yolde Formation at depths of 6916 ft and 6997 ft, respectively. This led to the identification of the gas-water contact at 6997 ft. Further analysis of the gas type using PVT analysis and the Soave-Redlich-Kwong (SRK) equation of state (EOS) model indicated that 80% of the gas in the reservoir was condensate gas. Temperature data ranged from 104 to 270 °F at the bottom hole and 109 °F to 281 °F in the formation. The calculated geothermal gradients of 0.0228 deg F/ft (52.49 °C/Km) and 0.0234 deg F/ft (42.62 °C/Km) suggested favorable conditions for gas reservoirs and hydrocarbon generation. The highest fluid mobility was observed at depths of 6916 ft, 7116.5 ft, and 7186.9 ft, indicating the presence of gas. The gamma ray log and resistivity log of the Kowell-1 well characterized the Yolde Formation as a substantial system of thin to medium sand/shale laminae. This research provides valuable insights into the hydrocarbon potential of the area, supporting future exploration and development efforts.

2025, Journal of Geodynamics

An inverse flexural plate method is used on five dip seismic lines across the northeastern Danish Central Graben to recover original unloaded plate parameters. The original plate showed remarkable consistency of parameters determined independently from each of the seismic lines with average rigidity D=102°-6-+°'2 Nm; bending moment M=1014"4-+°-SN, and dip angle 0=-7.5--.1.5 °. By sequentially adding the sedimentary units to the average "bare" basement, it is shown that the 3-D geometry of the basin had a major downward warp, and high sedimentary fill, to the SE at Triassic time, leaving the northern section open to possible erosion during Early and Middle Jurassic time. The deep southern basin was then filled by sediments during late Jurassic time, and a new depocenter created across the central and SW parts of the basin. This newer depocenter was then filled during Cretaceous time. The combined 3-D flexure of the basement plate and corresponding sediment fill behaviors with time are indicative of corresponcling lithologic variations across the basin and with suspected organic rich sediments. The integrated evolution of basement, sediments and depocenter behavior points to the utility of the inverse procedure for improving our understanding of basinal evolution. The relatively low values of rigidity compared to estimated oceanic crust values point to a thin crust below the sediments and to a higher heat flux through the basement relative to that through oceanic crustal material.

2025, Planetary and Space Science

Assuming that the long-wavelength geoid and topography of Venus are supported by both mantle convection and Airy isostasy, we propose a method to separate the dynamic and isostatic components of the Venusian gravity and topography with the aid of the dynamic admittance from numerical models of mantle convection and the isostatic admittance from an Airy isostatic model. The global crustal thickness is then calculated based on the isostatic component of the gravity and topography. The results show that some highland plateaus such as Ishtar Terra and Ovda Regio have thick crust, which are largely supported by isostatic compensation. Other highland plateaus such as Thetis and Phoebe Regiones appear to have superimposed contributions from crustal thickening and dynamic support. Volcanic rises such as Atla and Beta Regiones have thin crust, which is consistent with the postulation that these volcanic rises are mainly the products of dynamic uplift caused by mantle plumes.

2025, Earth and Planetary Science Letters

Venus's mantle convection model was studied in a three-dimensional spherical shell domain with depth-and temperature-dependent viscosity. Numerical results show that key observations of Venus including the number of major ''hotspot'' volcanic systems, spectral patterns of the surface topography and geoid at long-and intermediate-wavelengths can be explained in models that have a spinel-topost-spinel endothermic phase change of À 3.5 MPa/K Clapeyron slope and averaged mantle viscosity of 2 Â 10 21 Pa s (i.e., convective Rayleigh number of 1.8 Â 10 7 ). Our models with the endothermic phase change show relatively weak time-dependence, suggesting that the phase change may not be the primary cause for ''catastrophic'' resurfacing on Venus. Our calculations also show that Venus cannot have a weak asthenosphere that is similar to that on the Earth, in order to match the observations, thus supporting a key role of asthenosphere in producing plate tectonics.

2025

: Dynamic positioning of a moving platform is analyzed data from the Global Positioning System (GPS) acquired in Phase II of the Seafloor Benchmark Experiment on R/V Point Sur in August 1986. GPS position determinations are compared to simultaneous Mini-Ranger fixes. The GPS positions computed using only broadcast ephemeris data were within 20 m from the Mini-Ranger fixes when data from four satellites were used and within 30 m when data from three satellites and a geoidal height constraint were used. It was found that the position accuracy is degraded when data from a satellite reaching culmination is used.

2025, Mechanism of Sedimentary Basin Formation - Multidisciplinary Approach on Active Plate Margins

2025, ANAS Transactions, Earth Sciences

The eastern part of Central Gondwana and Eurasia is a tectonically complex region where several large tectonic plates interact-Eurasian, African, Arabian, Aegean-Anatolian, Iranian, and Sinai. However, consideration of only these plate interactions is insufficient. In addition to this interface, other regional geodynamic factors exist: the mantle rotating counterclockwise structure (MRCS), the Ural-African geoid anomaly, and the critical Earth latitude 35°. The Eurasia-Gondwana boundary divides the western partthe Aegean-Anatolian Plate and Mesozoic Terrane Belt (MTB) associated with the comparatively young Neoproterozoic Beltand the eastern part, the Iranian Plate, whose terranes are fragments of the Archean-Early Proterozoic Arabian craton. The Iranian lithospheric plate, a key player at the boundary between Eurasia and Gondwana, holds significant implications in the tectonic-geodynamic context. It tectonically influenced the South Caspian Basin (SCB) and recently revealed MTB. Novel tectonic, satellite-derived gravity, and magnetic maps of the Iranian Plate have been developed. Geodynamically, the considered tectonic units are located above the central and eastern parts of the MRCS. The Iranian Plate is above the eastern (periclinal) zone of the MRCS and, under its influence, moves northward. The movement of the western part and complex form of the Iranian Plate force the clockwise rotation of the SCB. A complex geodynamicgeophysical interaction of the central tectonic-geodynamic units in the region is shown. The influence of the recent geodynamic event-Akchagylian hydrospheric maximum on the ancient hominin dispersal in the region is exhibited. The carried analysis is essential to understand the role of the complex geodynamic interface in a transition zone between Eurasia and Gondwana.

2025

The eastern part of Central Gondwana and Eurasia is a tectonically complex region where several large tectonic plates interact -Eurasian, African, Arabian, Aegean-Anatolian, Iranian, and Sinai. However, consideration of only these plate interactions is insufficient. In addition to this interface, other regional geodynamic factors exist: the mantle rotating counterclockwise structure (MRCS), the Ural-African geoid anomaly, and the critical Earth latitude 35°. The Eurasia-Gondwana boundary divides the western partthe Aegean-Anatolian Plate and Mesozoic Terrane Belt (MTB) associated with the comparatively young Neoproterozoic Beltand the eastern part, the Iranian Plate, whose terranes are fragments of the Archean-Early Proterozoic Arabian craton. The Iranian lithospheric plate, a key player at the boundary between Eurasia and Gondwana, holds significant implications in the tectonic-geodynamic context. It tectonically influenced the South Caspian Basin (SCB) and recently revealed MTB. Novel tectonic, satellite-derived gravity, and magnetic maps of the Iranian Plate have been developed. Geodynamically, the considered tectonic units are located above the central and eastern parts of the MRCS. The Iranian Plate is above the eastern (periclinal) zone of the MRCS and, under its influence, moves northward. The movement of the western part and complex form of the Iranian Plate force the clockwise rotation of the SCB. A complex geodynamicgeophysical interaction of the central tectonic-geodynamic units in the region is shown. The influence of the recent geodynamic event -Akchagylian hydrospheric maximum on the ancient hominin dispersal in the region is exhibited. The carried analysis is essential to understand the role of the complex geodynamic interface in a transition zone between Eurasia and Gondwana.

2025, Journal of African Earth Sciences

Major, trace element and isotopic data for mafic to peralkaline silicic volcanic rocks from the northern sector of the main Ethiopian rift are discussed with the aim of placing constraints on processes of magma genesis and evolution and to present models for magma plumbing systems of rift volcanoes. Basalts straddle the subalkaline-alkaline boundary and exhibit important variations of incompatible element abundances and ratios. Silicic rocks consist of dominant pantellerites and minor comendites and trachytes, although some volcanoes along the rift shoulders consist entirely or predominantly of trachytes. Rocks with intermediate compositions are very scarce. Mafic and silicic rocks exhibit similar values as some basalts for many incompatible element and radiogenic isotopic ratios. Geochemical and petrological modelling shows that the most likely petrogenetic process for rift magmatism is a derivation of rhyolites from basalts by dominant fractional crystallisation occurring at shallow depths. Variations of incompatible element ratios and radiogenic isotopes in the basalts suggest heterogeneous sources and significant interaction with the crust. In contrast, the role of crustal assimilation during evolution of silicic magmas is negligible. It is suggested that large amounts of basalts were emplaced both into the lower continental crust, and at shallow depths. Shallow level fractional crystallisation generated zoned magma chambers with rhyolitic melts accumulating at the top, and mafic magmas ponding at the bottom. Volcanic activity was fed preferentially by the upper rhyolitic layer, whereas mafic magmas were erupted only accidentally, when extensional faults intersected the bottom of shallow reservoirs or tapped directly the deep magma chambers. The presence of trachytic volcanoes along the rift shoulders could result from clinopyroxene-dominated high-pressure basalt fractionation, which did not allow melts to reach rhyolitic compositions. Satellite imagery and field studies reveal the occurrence of a large number of caldera collapses in the main Ethiopian rift, suggesting that several magma chambers have been formed at shallow depths, possibly favoured by block tilting and strike-slip faulting. This explains the huge amounts of silicic rocks along the northern Ethiopian rift. The occurrence of huge magma reservoirs is also supported by positive gravity anomalies detected by previous studies beneath several silicic volcanic centres.

2025, Open Geosciences

The aim of the present work is to evaluate the stress direction and the tectonic trends of the study area using magnetic anisotropy and potential field data interpretations (Bouguer and aeromagnetic). The specific objective of the gravity and aeromagnetic interpretation is to establish the trend and depth of the structural configuration of the basement rocks. Horizontal gradient techniques could to delineate directions of deep sources and enabled tracing several faults, lineaments and tectonic boundaries of basement rocks. The trend analysis shows N40°–50°W, N10°–20°W and N10°–20°E which may be related to the Gulf of Suez, Red Sea and Gulf of Aqaba stresses. However, Euler Deconvolution technique was applied using the aeromagnetic data to provide reliable information about penetrated source depth (100 m and ∼10.0 km) and trends of the subsurface sources (principally in NW and NE directions). Moreover, representative 72 oriented rock samples have been collected from seven sites in th...

2025, Journal of African Earth Sciences

Combined 3-D interpretations of gravity and aeromagnetic data have been used in addition to continental and marine seismic profiles, well logs and geological cross-sections. The combination of gravity and magnetic data has improved the geometry and the density distribution in the 3-D calculated profiles. Results of the current work reveal possible crustal thickness and density distribution between the sedimentary cover and the upper mantle including the Moho discontinuity. The Moho depth map of the region, as obtained from the 3-D modeling exhibits various crustal thickness distributions. The type of crust changes gradually from continental to oceanic, from north to south. The zone of crustal thinning coincides mostly with zones of low-density, heated anomalous upper mantle beneath the rift floor (7 km). The eastern plateaus (the Red Sea hills) show by far the largest crustal thickness in the region (32 km). The Moho relief, as indicated from magnetic interpretation, shows a poor flattening especially in the eastern region. This is contrary to what is given by other authors. However, the present results are in good agreement with the geothermal gradient values in the Red Sea. The interpretation of magnetic data of the Red Sea Rift shows that the spreading rate of the part south of latitude 26.5°N agrees well with the theoretical model, in the order of 0.7 cm/yr. Less agreement has been obtained in the part north of latitude 27.5°N. The magnetic anomalies along the axial portion of the rift floor, as deduced from the results of the regional and residual separation and the 3-D magnetic modeling, are mainly caused by the oceanic crustal structures beneath the graben.

2025, Marine and Petroleum Geology

The East Orphan, Porcupine, and Galicia Interior basins are several of the most promising basins for hydrocarbon exploration along the rifted continental margins of the southern North Atlantic Ocean. Despite having formed at similar geological times, the basins exhibit fundamental differences in symmetry, crustal thickness, sedimentary cover thickness, and amount of extension. Interpretation of seismic reflection and well data was integrated with published 3D grids of depth-to-basement and Moho proxy depth to interpret and restore select seismic reflection lines. Publicly available kinematic evolution models were also integrated to evaluate and compare the restored seismic reflection lines in a more global regional context. Interpretation of five seismo-stratigraphic units and three tectonostratigraphic megasequences along the East Orphan, Porcupine, and Galicia Interior basins reveals similar seismic character for each unit and comparable tectonic history. The structural restoration of the selected lines indicates that evolution, sedimentary cover thickness, faulting style, crustal structure, and kinematic evolution of the East Orphan and Porcupine basins differ significantly. A variable and asymmetrical crustal structure is found in the East Orphan Basin contrasting with the elongated and symmetric Porcupine and Galicia Interior basins. Rift domain maps of the three basins reveal that they are each underlain by hyperextended crust, with possible exhumed mantle in the centre of the Porcupine Basin. Based on a holistic analysis of the results obtained, the linkage between the East Orphan and the Porcupine basins seems implausible, but rather a contemporaneous relationship is interpreted. Moreover, a potential connection between the Galicia Interior Basin and the Porcupine Basin during the Early to Late Jurassic is proposed. Such scenarios imply an oblique and synchronous rifting evolution around the Bay of Biscay triple junction of the southern North Atlantic.

2025, Bulletin of Geography- Physical Geography Series

The Palu-Koro Fault system in Central Sulawesi is a major strike-slip fault associated with signifi cant seismic hazards. This study investigates the fault dynamics and associated surface ruptures using gravity anomaly data and derivative-based geophysical methods. The Simple Bouguer Anomaly (SBA) values, ranging from-2 to 56 mGal, reveal substantial density contrasts in the subsurface, delineating fault boundaries and localised geological structures. Residual anomaly maps highlight sharp density gradients, which correspond to active fault zones. The derivative analyses, including First Horizontal Derivative (FHD) and Second Vertical Derivative (SVD), further refi ne the fault geometry and movement mechanisms, confi rming the predominantly strike-slip nature of the Palu-Koro Fault, with localised normal faulting in certain segments, particularly in pull-apart basins and fault stepovers. The identifi ed fault structures are consistent with previously mapped surface ruptures and aftershock distributions, indicating a strong correlation between gravity-derived density contrasts and active fault segmentation. These fi ndings offer critical insights into fault behaviour, contributing to more accurate seismic hazard assessments and disaster mitigation strategies. The results reinforce the importance of gravity-based geophysical techniques in fault characterisation and highlight their potential for integration with other geophysical datasets in seismic hazard analysis.

2025, Geophysical monograph

Detailed three-dimensional polygonal prism models of two large western Pacific seamounts show that the 135 mgal difference in the observed sea surface gravity over the two can be best explained by similar mean densities (2.6 gjcm 3 ) and crustal thickening under one seamount (Airy isostatic compensation). Observed calculated residuals are further reduced by including dense (2.9 gjcm 3 ) verti cal feeder pipes or volcanic conduits in the models. Dense conduits or fracture zones 5 to 17 km in diameter are located under many, if not all, craters on volcanic islands and seamounts. Results from the detailed seamount studies can be generalized using exact expressions for the on-axis vertical component of gravity for cones or frustrums of cones. Seamount isostatic compensation levels can then be rapidly estimated by iteratively inverting the on-axis gravity. The estima tion algorithm is independent of mechanical assumptions regarding oceanic lithosphere and is particularly useful for the rapid evaluation oflarge data sets. The results and associated uncertainties are compa rable to those of the detailed three-dimensional models and frequency domain studies. As predicted by cooling plate models, the estimated Airy (local) compensation levels p. for seamounts are inversely pro portional to the root ofthe seafloor age at the time ofloading t: p.(%) = 68 -5.6t 1 / 2 • A map of depth-corrected on-axis gravity values for western Pacific seamounts indicates that seamounts with similar p. 'fBlues tend to form clusters.

2025, BSGF - Earth Sciences Bulletin

The Djourdé-Sinassi magmatic-migmatitic complex is part of the juvenile Neoproterozoic Garoua Domain located in Northern Cameroon. It is surrounded by the Zalbi, Poli and Rey-Bouba greenstone belts, limited to the east by the sinistral Tcholliré-Banyo Shear zone and to the south by the Poli Thrust System. The Djourdé-Sinassi magmatic-migmatitic complex is subdivided into a western magmatic domain made of diorite, tonalite, granodiorite, with numerous enclaves of mafic and ultramafic rocks, and an eastern domain dominated by metatexite migmatites enclosing ubiquitous mafic to ultramafic rafts. The plutonic rocks of the western domain display a gently dipping to vertical magmatic fabric with variable trends. Locally, trains of hornblendite enclaves with lobate boundaries and dismembered into a network of felsic veins points to injection of mafic magma that mingled with a host magmatic mush and/or partially molten rocks. The migmatites display a foliation delineated by the alternation of leucosome and mesosome layers, that are mainly subvertical and wrapped around the metric to kilometric size rafts of mafic and ultramafic rocks. A texturally continuous network of leucosome veins concordant to discordant relative to the syn-migmatitic foliation and the mineral assemblage attests for syntectonic melt segregation under granulite facies conditions (Hbl þ Pl ± Bt ± Grt±Opx±Cpx ; peak: ≥800 °C/8-10 kbar). The magmatic fabric of plutonic rocks and the syn-migmatitic foliation are locally transposed into subvertical shear zones with a steeply plunging mineral and stretching lineation. Kinematic criteria are identified in the subhorizontal plane perpendicular to the lineation, which indicates that deformation was not plane strain and occurred in 3D. N-S to NE-SW striking shear zones are sinistral whereas E-W to WNW-ESE trending ones are dextral. These shear zones first developed in the presence of melt but then under solid-state during progressive retrogression from amphibolite to greenschist facies (AbþQtz þ Ep ± Op ± ChlþSerþEp). These data suggest that the Djourdé-Sinassi magmatic-migmatitic complex corresponds to the former root of the Central African Orogenic Belt originating from partial melting of a juvenile mafic crust. This root has been vertically extruded under a pure-shear dominated constrictional regime with vertical stretching in the presence of melt coeval with the injection of mantle-derived mafic magmas and was then progressively exhumed towards the surface. This deformation pattern is consistent with the position of the Sinassi complex surrounded by greenstone belts and on a larger scale, confined in between the West African À Congo cratons and Saharan metacraton.

2025, Terrestrial, Atmospheric and Oceanic Sciences

On 26 December 2006, two M L = 7.0 events occurred offshore south of Pingtung; one is associated with a normal-faulting and the other with a strike-slip faulting. The area where these earthquakes were located is not usually expected to have large earthquakes. We deployed 11 short period OBSs over the source zone for one week and recorded a series of aftershocks which were also recorded on land at the CWB network stations. The joint dataset made it possible for us to perform a 3-D velocity tomography and earthquake relocation in this region, where the velocity structures were not well known and location of earthquakes with only land data was uncertain. The tomographic results show a prominent high Vp perturbation zone (HVPZ) that we consider as the uppermost mantle of the subducted plate dipping from SW to NE beneath southern Taiwan. Most of the relocated earthquakes are distributed just above the HVPZ or near and along the bottom of a relatively low velocity subducted crust. Our results show that the subducted and bent Eurasian plate off SW Taiwan could have been unbent and become an upwards concave geometry for the upper 30 km. The main shock is near the bottom of the inflected surface. The distribution of the earthquake sequence generally displays in a NW-SE direction, coinciding with the plate convergence orientation between the Philippine Sea Plate and Eurasian Plate. This orientation also follows a relatively low Bouguer gravity anomaly stripe that is due to a heavy loading of the Taiwan orogen on the east-dipping Eurasian Plate. Considering that the hypocenter of the first main-shock is near the bottom of the aftershocks, we suggest that the first normal faulting earthquake was caused by an unbending effect in the subducting crust and this event triggered the release of accumulated energy between the Philippine Sea Plate and Eurasian Plate. Thus, we suggest that the rupture surface of the Pingtung earthquake sequence had propagated upwards and northwestward in the direction of plate convergence.

2025, GEOPHYSICS

This paper presents a gravity inversion method for determining the volumes of bodies with pre‐established density contrasts. The method works step‐by‐step on a prismatic partition of the subsurface volume, expanding the anomalous bodies to fit the observed gravity values in a systematic exploration of model possibilities. The process is treated in a 3-D context; at the same time, it can determine a simple regional trend. Moreover, positive and negative density contrasts are simultaneously accepted. The solution is obtained by a double condition: (1) the 𝓁2-fitness to the observed gravity data (model fitness) and (2) the minimization of the total (weighted) anomalous mass (model smoothness). A positive parameter is used to balance the two minimization terms. The method is applied to a simulated example and also to a real example: the volcanic island of Gran Canaria (Canary Islands, Spain). In both cases, the results obtained show the possibilities of the method.

2025, Journal of Geodynamics

Since 1987, gravity tide observations have been conducted on the island of Lanzarote, with different gravimeters at different locations. Very anomalous values of heat flow data have also been collected in the Timanfaya National Park (southwestern part of the island). Seismic experiments provide us a crustal model of the island, with an average depth of 11.5 km. The gravity tide observations show that, after correction of the indirect oceanic effect using global and local ocean charts, the cosine component of the final residual vector for station Cueva de los Verdes (northeastern of the island) depends on the ocean model considered. On the other side, the final results change greatly if we take into account the porosity effects of the lava rock at this station. Then, the cosine component of the final residual is closer to, or greater than, zero. In Timanfaya station (located in the Timanfaya National Park), we observe that both M 2 and O 1 residuals are equally large. Their phases are more consistent with a body tide effect than with an ocean loading effect. Furthermore, the negative sign of the residuals looks consistent with the response of a porous or cavity-filled, local, upper crust under the influence of tidal strain. Therefore, we found a similar explanation for the existence of negative values of the final residuals at both stations. Our study seems to suggests the lack of correlation between heat flow and tidal gravity anomalies. Nevertheless, we must point out again the existing necessity of theoretical studies and highest quality observations to answer the different questions regarding the significance of the tidal gravity anomaly-heat flow trends. Also, the effect of tidal strain in a porous or cavity-filled, local, upper crust should be considered.

2025

In January 1988, scientists from over 25 organizations in ! 3 countries and territories cooperated in the largest Global Positioning System (GPS) campaign in t_he world to date (Table !). 43 GPS receivers collected approximately 590... more

2025, Science

THE ARTICLE "BUSH AND KERRY OFFER THEIR views on science" (1 Oct., p. 46) raises an important question. Is it known for certain that Bush and Kerry actually took the time to read the campaign responses before they were returned to Science, or were the responses stock answers handled by staff? If it is not known, then in future campaigns, it might be wise to include a final question: "Mr. Candidate, did you personally read and approve of the responses to our questions?" The answer, or lack thereof, might say more about the priority of science to the candidate than any other question you ask.

2025, 2018 4th International Conference on Science and Technology (ICST)

Conversion of geodetic height to orthometric height requires geoid to transform geometric elevation above ellipsoid into physical elevation above mean sea level. The need of accurate geoid is increasing as many leveling benchmarks have lost and deformed due to city development and natural activities. This paper presents geoid determination based on combination of gravity disturbances data and gravity anomalies data. Gravity disturbances were computed from 185 terrestrial gravity data. Gravity data were measured on March 2016 using Scintrex CG-5 gravimeter. All gravity stations coordinates were measured using rapid static method of GNSS to achieve sub-meter accuracy. Gravity anomalies data for improving the accuracy of the geoid models were measured by some government and private agencies using analogue gravimeters. It consisted of 10,149 data and covered whole Java island which was not less than 2 arc degree of latitude by 10 arc degree of longitude. Gravity disturbances of the city...

2025

Ethiopia is located in the horn of Africa with a population of over 90 million. The economy is non oil driven and has grown in double digits during the last 10 consecutive years. The continuous economic growth has brought about a significant growth of energy demand including electricity. It is required to enhance the current installed electrical capacity of 2200 MW to 10,000 MW in a couple of years, to meet the electricity demand. The energy policy of the country allows developing electricity from all indigenous renewable energy resources including geothermal and private sector participations are encouraged to speed up the development process. Ethiopia is endowed with high enthalpy geothermal resources, currently estimated to reach 10, 800 MW potential, distributed over 22 prospect areas. Since recent years a number of geothermal projects have been initiated and are being implemented, to advance geothermal development in the country. These include: (i) geothermal master plan study (...

2025, Geophysical Journal International

We use two gravity profiles that we measured across Central Nepal, in conjunction with existing data, to constrain the mechanical behaviour and the petrological structure of the lithosphere in the Himalayan collision zone. The data show (1) overcompensation of the foreland and undercompensation of the Higher Himalaya, as expected from the flexural support of the range; (2) a steep gravity gradient of the order of 1.3 mgal km x1 beneath the Higher Himalaya, suggesting a locally steeper Moho; and (3) a 10 km wide hinge in southern Tibet. We compare these data with a 2-D mechanical model in which the Indian lithosphere is flexed down by the advancing front of the range and sedimentation in the foreland. The model assumes brittle Coulomb failure and nonlinear ductile flow that depends on local temperature, which is computed from a steadystate thermal model. The computed Moho fits seismological constraints and is consistent with the main trends in the observed Bouguer anomaly. It predicts an equivalent elastic thickness of 40-50 km in the foreland. The flexural rigidity decreases northwards due to thermal and flexural weakening, resulting in a steeper Moho dip beneath the high range. Residuals at short wavelengths (over distances of 20-30 km) are interpreted in terms of (1) sediment compaction in the foreland (Dr=150 kg m x3 between the Lower and Middle Siwaliks); (2) the contact between the Tertiary molasse and the meta-sediments of the Lesser Himalaya at the MBT (Dr=220 kg m x3 ); and (3) the Palung granite intrusion in the Lesser Himalaya (Dr=80 kg m x3 ). Finally, if petrological transformations expected from the local (P, T) are assumed, a gravity signature of the order of 250 mgal is predicted north of the Lesser Himalaya, essentially due to eclogitization of the lower crust, which is inconsistent with the gravity data. We conclude that eclogitization of the Indian crust does not take place as expected from a steady-state local equilibrium assumption. We show, however, that eclogitization might actually occur beneath southern Tibet, where it could explain the hinge observed in the gravity data. We suspect that these eclogites are subducted with the Indian lithosphere.

2025, Çukurova Üniversitesi Mühendislik Mimarlık Fakültesi Dergisi

Çalışma alanı, Afyonkarahisar iline bağlı Dinar ilçesinin yaklaşık 10 km kuzeydoğusunda bulunan ve Göller bölgesinin oluşumunu da kontrol eden horst-graben sistemi içerisinde yer almaktadır. Çalışılan alan; horst-graben sistemi ve normal-verev atımlı faylar tarafından şekillendirilmiştir. Çalışmaların yürütüldüğü Dombayova grabeni yaklaşık olarak 5 ile 7 km genişliğinde, 20 km uzunluğunda bir çöküntü bölgesidir. Dombayova grabeni; kenarlarda alüvyon yelpazeleri ve yamaç molozları gibi genellikle orta-iri taneli birimlerden, orta kısımlarda ise kenar birimlerle yanal-düşey geçişli, kiltaşı, silttaşı, kumtaşı, çamurtaşı ve çok pekişmemiş kırıntılı birimlerden oluşmaktadır. Çalışma alanındaki aktif tektonizma nedeniyle sahanın özellikle doğu kenarlarındaki birimlerde gözle görülebilen eğimlenmeler dikkat çekmektedir. Ayrıca bu durum, sondajlardan alınan karotlarda da gözlendiği üzere bazıalanlarda yer yer sıkı kıvrımlanmalara sebebiyet vermiştir. Bu süreç sahada normal faylanmaların oluşumu ile birlikte verev atımlı faylanmaların gelişimini de sağlamıştır. Dombayova grabeni; batı ve doğu kenarlarından, havza merkezine doğru eğimli olan normal ve verev atımlı faylarla temsil edilmektedir.
Sondaj çalışmalarında gözlemlendiği üzere, havzadaki faylar mevcut birimlerin çok kısa mesafelerde farklı seviyelerde oluşmasına neden olmuştur. Benzer ötelenmelere linyit damarlarında da gözlenmiştir.
Bu nedenle kömür korelasyonu ve damar modellenmesinde zorluklarla karşılaşılmıştır. Söz konusu grabende yapılan sondaj çalışmaları ile yaklaşık olarak 1,525 milyar ton (± 100 milyon ton) rezerve sahip Geç Pliyosen-Kuvarterner yaşlı çökellerin altında oluşmuş, Miyosen-Pliyosen yaşlı linyitlerin varlığı tespit edilmiştir. Sahadaki linyitlerin kalınlıkları havza kenarlarında birkaç cm’den başlayıp, havza merkezine doğru yer yer yüzlerce metre kalınlığa ulaşmaktadır. Yapılan laboratuvar analizleri neticesinde bu linyitlerin ortalama olarak 1783 kcal/kg alt ısıl değere, %40,57 nem, %18,97 kül, %27,65 uçucu madde, %12,81 sabit karbon, %0,73 külde kükürt ve %1,25 toplam kükürt değerlerine sahip olduğu tespit edilmiştir.

2025

The mid-latitudes of Mars have typically a dissected mantle of thin material. Within this mantle we observe scallops that are similar to the south polar "Swiss-cheese" features. We study these landforms in order to determine... more

2025, GEOPHYSICS

We present a gravity interpretation method for estimating the relief of an arbitrary interface separating two homogeneous media. The upper medium is discretized into rectangular, juxtaposed prisms whose thicknesses represent the depths to the interface and are the parameters to be estimated from the gravity anomaly. The density contrast of each prism is assumed to be constant and known. To stabilize the inversion, we introduce two kinds of constraints on the depths. The first one requires proximity between the observed and computed depths at isolated points such as those obtained from boreholes (absolute equality constraint). The second one requires that groups of depths approximately follow an established linear relationship among the depths (relative equality constraint). Both kinds of constraints are imposed in the least‐squares sense. We illustrate the method performance by applying it to a synthetic anomaly produced by a simulated basement relief consisting of four narrow and a...

2025, Pure and Applied Geophysics

The Tilt-depth method has been widely used to determinate the source depth of a magnetic anomaly. In the present study, we deduce similar Tilt-depth methods for both magnetic and gravity data based on the contact and sphere models and obtain the same equation for a gravity anomaly as that for a magnetic anomaly. The theoretical equations and the model tests show that the routine Tilt-depth method would result in unreliable depth estimation for deep sources. This is due to that the contact model is no longer valid for causative sources under the condition in which the depths of causative sources are significantly larger than their horizontal lengths. Accordingly, we suggest that the Tilt-depth derived from the contact model can be used to detect a shallow source, whereas the Tilt-depth derived from the sphere model can be used to detect a deep source. We propose a weighting method based on the estimated depths from both the contact model and the sphere model to estimate the depth for real data. The model tests suggest that the determined depths from the contact model and the sphere model are shallower and deeper, respectively, than the real depth, while the estimated depth from the proposed method is more close to the actual depth. In the application to the Weigang iron ore located in Jiangsu province, China, the routine Tilt-depth method results in -76% relative error, whereas the proposed method obtains the reliable depth estimation compared with the drill holes. In addition, the proposed method works well in the application for the Shijiaquan iron ore located in Shandong province, China. These results indicate that the proposed weighting equation is a general improvement.

2025

Gravimetry is the most suitable geophysical method for identifying subsurface cavities in urban or industrial environments, as it is unaffected by nearby electromagnetic disturbances. In this study, we used gravimetric geophysical method to understand the land subsidence, collapses, and fissures observed around the sealed Albian drilling site located in the M'Rara region of Northeast of Algeria. Particularly, we would like study the geological observed phenomena and its potential association with the presence of a cavity within the salt layer. According to the stratigraphic column, a salt layer was located at 936 m depth. To better understand the subsurface conditions, A new gravimetric survey was conducted to image the density distribution and identify anomalous zones associated with subsurface cavities. Various gravity data processing techniques, including polynomial fitting of different orders, vertical and horizontal gradient analysis, and three-dimensional inversion, were applied. These methods aim to evaluate the relationship between detected gravity anomalies and the underlying structures, with a focus on their possible correlation with cavities within the salt layer. The gravimetric evidence suggest that the hydraulic drilling is not the cause of the observed phenomena. These cavities are likely formed by water circulation in the subsoil, originating from the Retem Valley.

2025

The complex wavelet and ridgelet transforms are used in the potential field data interpretation for identifying the buried structures responsible for potential field anomalies. Its basis is the use of particular analyzing wavelets belonging to the Poisson semigroup that possess amazing properties regarding potential fields. In fact, the analyzed anomaly displays a conical signature in the wavelet domain and whose apex is pointing out at the causative homogeneous structure. Fundamentally, the interpretation is performed in the upward-continued domain where, the dilation of the wavelet transform is the upward-continuation altitude. This confers on the wavelet transform a considerable advantage: its robustness with respect to noise. The method is also developed to identify the depth, horizontal positions, size, strike direction, dips and shape of elongated 3D structures such as finite-dimensional dykes and faults. For this type of anomaly, the 2D wavelet transform corresponds to the ridgelet transform performed in the Radon domain, where elongated anomalies are recognized by high amplitude signatures. A reminder of the developed theory and applications in the 2D and 3D cases on real case studies are shown.

2025, Journal of Geoscience and Environment Protection

2025, Jurnal Pendidikan Fisika dan Teknologi

Time lapse or 4D gravity is the development of gravity methods with the fourth dimension is time. This method is characterized by repetitive measurements over a period of time using a high-precision gravity measuring device (gravimeter) which is supported by high accuracy measurement of position. In the case of a fault that triggers an earthquake, layers that have a different density between layers will have the effect of changing the measured value of the gravitational field on the surface. The difference in the value of measured gravity before and after the occurrence of a fault as a result of an earthquake is what gives the value of time lapse gravity. The model of position displacement of the layers before and after the earthquake, provides a model of density between times whose gravitational anomalies can be calculated by forward response. The response of time-lapse forward model (synthetic data) is then optimized to obtain an inversion model. Inversion programming is made usin...

2025

The objective and available data for determining the geopotential number IHRS of the CORS
UYPT and UYTA stations are described, including a review of the quasi-geoidal and geoid models
used and the tidal systems used.

2025, Tectonophysics

The Wilkes Subglacial Basin, in the hinterland of the Transantarctic Mountains, represents one of the least understood continental-scale features in Antarctica. Aeromagnetic data suggests that this basin may be imposed on a Ross age back arc region adjacent to the East Antarctic Craton. However, the evolution of the deeper crustal structure is disputed. Here, we present new airborne gravity data that reveals the crustal architecture of the northern Wilkes Subglacial Basin. Our gravity models indicate that the crust under the northern Wilkes Subglacial Basin is 30-35 km thick, i.e. ca 5-10 km thinner than imaged under the Transantarctic Mountains, and ~15 km thinner than predicted from some flexural and seismic models in the southern Wilkes Basin. We suggest that crustal thickening under northern Victoria Land reflects Ross-age (ca 500 Ma) orogenic events. Airy isostatic anomalies along both flanks of the Wilkes Basin reveal major inherited tectonic structures, which likely controlled the basin location, supporting aeromagnetic interpretations of the Wilkes Subglacial Basin as a structurally controlled basin. The positive anomaly along the western margin of the basin defines the boundary between the East Antarctic Craton and the Ross Orogen, and the anomaly along its eastern flank likely reflects high-grade rocks of the central Wilson Terrane. Our models indicate that the crust is ~5 km thinner beneath the northern Wilkes Basin, compared to formerly contiguous segments of the Delamerian Orogen in south-eastern Australia. The thinner crust may be linked to: i) back-arc basin formation or orogenic collapse processes and segmentation within the Ross\Delamerian Orogen, ii) Jurassic to Cretaceous extension prior to break-up between Australia and East Antarctica, iii) Cenozoic glacial erosion or most likely, iv) a combination of these processes.

2025, Journal of Geophysical Research: Solid Earth

Elastic half‐space models, widely used to interpret displacements and gravity data in active volcanic areas, usually compute the displacement response to dilatational sources that simulate a change in pressure of the magma chamber. Elastic‐gravitational models allow the computation of gravity, deformation, and gravitational potential changes due to pressurized magma cavities and intruding masses together. This type of model takes into account the mass interaction with the self‐gravitation of the Earth through coupling between model equations. We perform a dimensional analysis of the elastic‐gravitational model estimating the magnitude of intrusion mass and coupling effects at the space scale associated with volcano monitoring. We show that the intrusion mass cannot be neglected in the interpretation of gravity changes while displacements are primarily caused by pressurization. Therefore the intrusion of mass, together with the associated pressurization of the magma chamber, produces...

2025, Geophysical Research Letters

Volcanic activity produces deformation and gravity changes that many times can be used as precursors of future eruptions. Applying geodetic techniques to monitoring activity involves interpretation using deformation models. Usually gravity change data and displacement data are interpreted separately. We show, using modeling of deformation and gravity change data in Long Valley Caldera, California, USA, that this can lead to incorrect interpretations. The results obtained show that displacements and gravity changes must be interpreted together whenever possible and that elastic-gravitational models can be a far more appropriate approximation to problems of volcanic load in the crust than the more commonly used purely elastic models. Therefore it is necessary to change the philosophy normally used to interpret geodetic observations, improving the possibility of predicting future eruptions.

2025, Geophysical Research Letters

Volcanic activity produces deformation and gravity changes that many times can be used as precursors of future eruptions. Applying geodetic techniques to monitoring activity involves interpretation using deformation models. Usually, the observed changes of the deformation and gravity fields are interpreted seperately, not in a joint inversion. It can be difficult, if not impossible, to interpret the data coherently or correctly in terms of the characteristics of the intrusion or the deflation derived from the gravity changes with purely elastic models, as in the case of Mayon Volcano, Phillipines. We show that elastic-gravitational models can be used to interpret these cases simultaneously leading to a result that is more plausible on the basis of the available information. Thus, we may need to change the philosophy normally used to interpret geodetic observations. Interpretation as proposed in this work can significantly improve the possibility of predicting future eruptions.

2025

A new Earth Gravitational Model (EGM08) to degree 2160 has been released to IAG's EGM Evaluation Group. In this study, we evaluate EGM08 Tide Free Model by using regional gravity, quasi-geoid height and GPS/leveling data. The EGM08-derived quantities are compared with (1) the GPS/leveling quasi-geoid heights, (2) an existing GPS/leveling fitted regional quasi-geoid model (TG03), and (3) the surface gravity anomalies in Turkey. The differences between observed/computed and EGM08-derived quantities are investigated. The mean value and standard deviation of the differences between EGM08 derived and observed quantities are found to be -88.8 cm and 24.2 cm for GPS/leveling height anomalies, 27.1 cm and 75.3 cm for TG03 quasi-geoid heights, and 2.8 mGal and 17.1 mGal for surface gravity anomalies. As Turkish proprietary data were not used in EGM08 computations this work is believed to be an external check for EGM08.

2025, Arabian Journal of Geosciences

The Ghawar Anticline (GA) belongs to super-giant Rayn Anticlines in Eastern Saudi Arabia (ESA). The origin of GA is ascribed to basement-uplift, although, its evolution remains obscure due to inadequate knowledge on configuration of deeper crust and role of crust in producing the basement uplift. The nature of deeper crust is comprehended by an integrated crustal model utilizing DEM, Bouguer anomaly (BA) map, and high-pass-filtered residual BA map by using Laplacian operator, tilt derivative, theta maps, and Euler 3D convolution map on BA data. These maps prove helpful in delineating the structural outline of GA and its edge detection of the uplifted basement against the adjoining sub-basins. 2D gravity inversion for a traverse represents a model on subsurface mass anomalies extending from basement to Moho depth, for which, constraints are utilized based on the nature of seismogenic crust in ESA and available results of receiver function for four seismic stations. A 3-layer source on mass anomalies with depths of 3-5, 22.5, and 40 km is inferred. Poisson' ratio based on Vp/Vs values is high: 0.41-0.42 on its limbs to 0.44 at its median part, where the receiver function data reveals a zone of mantle uplift. Main results derived from Integrated Gravity Model underlying the traverse are as follows: (i) Moho is uplifted by ~9 km below GA, for a 220-km width, (ii) the zone of basement uplift in the top crust is ~4.5 km over a distance of ~75 km, where deep-penetrative faults assist the basement uplift, and (iii) a higher thermal regime probably influenced the crustal configuration below GA.

2025

A gravity base network is supposed to be a set of benchmarks uniformly distributed across the country and the absolute gravity values at the benchmarks are known to the best accessible accuracy. The gravity at the benchmark stations are either measured directly with absolute devices or transferred by gravity difference measurements by gravimeters from known stations. To decrease the accumulation

2025

Wavelet transform is an efficient technique to interpret the potential field data. The continuous wavelet transform is used to locate and characterize the source of the potential field by transferring the data into an auxiliary space. The technique has been tested on several synthetic source anomalies and applied to potential field data from Bay of Bengal. Using free air gravity and magnetic data the mean depth to causative sources indicates presence of lithospheric flexure at the central part of profile across 85°E ridge. Using free air gravity data, it is inferred that mean depth to causative sources decreases from west to east across 90°E ridge along MAN-01 profile which indicates increase of sediment thickness across the ridge from east to west. The technique gives mean depth of the causative sources without any a priori information which can be used as a initial model in any inversion algorithm.

2025, YOUNGSTER PHYSICS JOURNAL

Gravity method research has been done in Merapi Volcano area. The data has been measured by BPPTKG Yogyakarta team with the number of point as much as 164 points. The aim of this research are to identify the subsurface structure and locate the position of Merapi Volcano magma chamber, so that a gradient analysis and 2D modelling based on Bouguer anomaly has been done. Gradient analysis apply first horizontal and second vertical gradient that is used to know the location and the type of structure on the research area. The result from this research show Bouguer anomaly with range value around -8.79 mGal to 305.46 mGal. The 2D modelling show Merapi volcano subsurface model that consist of 5 layers with the position of magma chamber is located in the third layer about 3300 m below the Merapi summit or 700 m below the mean sea level. Based on gradient analysis, there is a normal dipfault structure. This faults is indicated to be formed a basin on the Merapi summit toward westward leading...

2025

This study was conducted to model the geothermal system Arjuno-Welirang northern part from the MT and gravity data. MT modeling done in 2D and gravity in 3D. From 2D MT model of North-South trending shows model 2 layer resistivity, ie resistivity low (<10 Ohm.m) associated with basalt lava rock with clay mineral alteration and an alleged caprock. And layer with moderate resistivity (60-100 Ohm.m) associated with the Lower Quaternary andesite-old who is the reservoir system. Distribution of Bouguer anomaly reflects the lithology of rock on the surface. Relatively low anomalies in the North (25-28 mGal) allegedly associated with pyroclastic flows. High anomaly in the South (> 43 mGal) associated with Mount Anjasmoro products spread to the South West section with the composition of andesitic-basaltic lava. 28-40 mGal anomalies are thought to relate to Lava Welirang I spread toward the center of the North with the composition of basalt lava. From 3D models Bouguer anomaly inversio...

2025, Geophysical Journal International

2025

Geothermal systems in the context of very active rifting, such as in the Republic of Djibouti, are complex to
characterize. Despite the numerous geoscientific studies conducted over decades in recognized prospects such as
Fiale Caldera and Gale-le-Koma in the Asal Rift, we do not understand well the mechanism of the geothermal
resources, their relationships with the heat source at depth and the recharge of water. In an attempt to progress in
this understanding, we present an analysis of 3-D gravity data inversion guided by a new three-dimensional
electrical model to obtain constrained density models for each geothermal site. These models along with the
resistivity model revealed highly fractured underground structures primarily influenced by two processes:
geothermal activity from the rift and structural control from the active rift tectonics. These models are in good
agreement with the lithology from boreholes, as well as with geochemical and hydrogeological data. The study
presents revised conceptual models for the two geothermal systems. These conceptual models consist of a shallow
reservoir and a deep reservoir at each site (Fiale Caldera and Gale-le-Koma geothermal prospects), primarily
recharged by seawater from the Bay of Ghoubbet and possibly by regional meteorological groundwater
recharges.

2025, AAPG Bulletin

Statistical Analysis of Correlation of Porosity and Permeability Determinations from Well Cuttings Using a Portable pNMR Apparatus with Conventional Core Analysis and Wireline Log Readings The porosity-permeabiUty (P-K) analyzer is a field-portable device that uses the principle of pulsed nuclear magnetic resonance to determine the content of hydrogen nuclei present in the free and bound water in rock samples. Using a simple dual-water model, these values may be used to calculate total porosity, free fluid index, and permeability index. The principle of measurement is such as to require relatively small sample volumes and reliable results can be obtained from well-cuttings samples or 3-mm diameter core plugs. Results from the P-K analyzer are responsive to total fluid-filled pore space in the rock, although it is possible to distinguish free, i.e., movable, fluid from bound fluid, i.e., at grain boundaries or within restricted pores and in argillaceous rocks. The P-K response is entirely independent of formation lithology, mineralogy, or salinity of pore waters and is not appreciably affected by the presence of light oils. The presence of free or dissolved gases in the sample will have a significant effect on response. However, samples are brine flushed and aspirated in preparation for analysis in order to remove this effect. We see, from these differences, that results from the P-K method cannot be expected to show a direct one-to-one correlation with those from conventional core analysis or the wireline density or neutron logging tools. A statistical analysis is presented using data from each of the analytical methods and types and conditions of sample. A strong correlation is demonstrated both visually and statistically, thereby providing verification of the P-K method and facilitating its use alongside data previously obtained by more conventional methods.

2025, Pure and Applied Geophysics

Gravity data, integrated with seismic refraction/reflection data, well data and geological investigations, were used to determine the location of the paleogeographic boundary between the Precambrian Saharan domain and the younger Tunisian Atlas domain. This boundary (North Saharan Flexure or NSF) has not been as clearly defined as it has been to the west in Algeria and Morocco. The gravity data analysis, which included the construction of complete Bouguer and residual gravity anomaly maps, revealed that the Atlasic domain is characterized by relative negative gravity anomalies and numerous linear gravity trends implying a thick and deformed sediment cover. The Saharan domain is characterized by relatively positive gravity anomalies with few gravity trends implying a thin and relatively undeformed sediment cover. An edge-enhancement analysis of the residual gravity anomalies revealed that the NSF is characterized by a series of discontinuous east-and northwest-trending linear anomalies south of 34°N that are not related to the well-known faults within the Gafsa and Accident de Medenine regions. Based on the continuity of the amplitudes of seismic reflection data and the trends of the residual gravity anomalies, the NSF is not an abrupt discontinuity but a series of step faults dipping toward the Atlasic domain. To obtain a more quantitative representation of the southern edge of Tunisian Atlas, a regional gravity model constrained by two wells and seismic reflection/refraction data was constructed along a north-south trending profile which confirms the presence of thicker sediments north of the NSF. Our analysis shows that the NSF has controlled the depositional environment of the sedimentary rocks within the region since at least Triassic time and has acted as a barrier to Atlasic deformation south of the NSF. The NSF is considered an important tectonic feature that has controlled the paleogeographic evolution of the southern margin of the Tethys Ocean, and it continues to be active today based on seismicity hazard studies.