Moho Depth Research Articles

Multi-Elevations Upward Continuation Method to Depth Detection of the Main Crustal Layers in Western Desert of Iraq

The upward continuation technique was applied to the gravity and RTP magnetic data to obtain the residual anomalies maps in the western part of Iraq. Twelve upward elevation residual gravity maps and another twelve upward elevation residual RTP magnetic were determined using the same twelve upward continuation elevations. The applied upward elevations range from 1000 to 55000 m. The total range of the residual anomalies maps (Color Bar range) of gravity and RTP magnetic were plotted against the upward elevations. Five segments and four intersection points were obtained for the gravity and magnetic data. The trace of these intersection points on the upward elevation axis approximately indicate the following values 4.4-5, 12.8-13.5, 27-24, and 39-39.6 km. These values may indicate the depth of the following layer boundaries, the Burj Formation ( Mid-Cambrian), basement, mid layer in the basement rocks, and the Moho depth. The authors believe it is possible to apply the upward continuation to find the main layers which show abrupt change in the physical properties

Constraints from lamprophyre petrogenesis on the timing of Eocene lithospheric thinning and associated rifting of Borneo and Sulawesi

The petrogenetic history of well characterised magmatic rocks may contain invaluable information of paleo-lithospheric thickness and structure that can inform on tectonic evolution. Petrographically distinctive rocks, such as lamprophyres, provide temporal and spatial constraints to build, assess, and verify tectonic models.An alkaline lamprophyre dyke that intrudes the rift-related sediments of the Eocene Tanjung Formation of the Senakin Peninsula in South Kalimantan, Indonesia has been investigated using petrology, whole rock geochemistry and Ar-Ar geochronology.The Senakin lamprophyre dyke is mostly geochemically homogenous but petrographically stratified with vesicle free monchiquite alkaline lamprophyre mineralogy at the base and an amygdale bearing kaersutite phenocryst free upper zone. The major and trace element chemistry is consistent with an intra-plate Ocean Island Basalt like affinity. 40Ar/39Ar dating of hornblende and groundmass aliquots indicates an emplacement age of 37.45 ± 0.10 Ma (2σ), which is consistent with the Late Eocene age of the Tanjung Formation derived from microfossil analysis.The petrology and geochemistry of the Senakin lamprophyre dyke is consistent with magma genesis at > 2GPa beneath a thick lithosphere followed by fractional crystallisation at Moho depths equivalent to 0.5–0.8 GPa. This indicates a much thicker southeastern Kalimantan paleo-lithosphere. Lamprophyre magmatism was initiated by lithospheric extension associated with the opening of the Makassar Strait and also regional thermal upwelling. This extension continued to thin the lithosphere to its current thickness equivalent to 0.5 GPa.

Crustal deformation and thickness variation from Zagros to Alborz in Iran: New insights from H-κ-c method

The collision between Arabia and Eurasia has had a significant impact on the Iranian plateau, making it a prime location for investigating crustal deformation. The Neotethys Ocean closure and subsequent collision during the Cenozoic era led to extensive deformation in the northern part of the Iranian plateau, in particular development of the Alborz mountain range. In this study, we aim to determine crustal thickness and azimuthal anisotropic parameters in order to gain insights into the patterns of crustal deformation in the region. Using the H-κ-c method (Li et al., 2019), we conducted an investigation into the impact of seismic anisotropy on the estimation of the crustal thickness (H) and Vp/Vs ratio (κ) at 26 seismic stations. Our analysis unveiled significant variations in Moho depth across the studied region. The collisional zones featured a deeper Moho depth when compared to Central Iran. In particular, the Central Iran region demonstrated a relatively thinner crust, characterized by an average Moho depth of 43 km, while the Sanandaj-Sirjan zone showcased a thicker crust, boasting a Moho depth of 59 km. The Alborz mountain ranges demonstrated an average Moho depth of 50 km. Notably, the Central Iran stations exhibited elevated κ values, potentially attributable to fluid contents and thick sedimentary cover. To characterize the anisotropic properties of the crust, we employed curve fitting techniques on the sinusoidal moveouts of the Ps-converted phases originating from the Moho and major intracrustal interfaces. Our analysis identified intracrustal discontinuities at seven stations, indicating the presence of two distinct anisotropic crustal layers. These anisotropic layers displayed maximum delay times of up to 0.6 s. Furthermore, our examination of crustal and mantle anisotropy patterns revealed that the deformation observed in the region cannot be solely attributed to a vertically coherent regime.

Lithospheric and asthenospheric properties of the saharan platform inferred from potential field, geoid and heat flow data

In this paper, we construct a geophysical-based model of the crust and uppermost mantle to provide an understanding of the architecture of the intricate deep structures, and determine the origin of geothermal reservoirs within the Saharan platform. These structures influence the distribution of the geothermal resources in the eastern Algerian Sahara. This study illustrate the deep structures of the lithosphere and asthenosphere, extending to depths of ∼350 km. Heat flow values were measured from petroleum wells and calculated from the magnetic data. The estimation of lithospheric mantle density was at standard pressure-temperature (P-T) conditions. However, the layer thickness estimate was, based on coupled analysis of elevation-geoid anomaly information. Hence, thermal models were generated with respect to crustal, crystalline basement and lithospheric-asthenospheric boundaries. Analyses of gravity, geoid and topographic dataset, shows that the Moho depth is deeper towards the southeastern limits, and shallower across the M'zab dorsal and the Hassi R'mel basin. The Moho temperature estimates were between 415 and 498 °C, typical of a cold stable cratonic crust. Results of lithospheric thickness were between 177 and 222 km, with maximum depth occurring within the northwestern limits of the Saharan platform. Hence, this paper provides an initial comprehensive geodynamic model, and gives insight to the origin of the geothermal potential of the Eastern Sahara.

CRUSTAL THICKNESS BENEATH UTAKO ABUJA USING RECEIVER FUNCTION ANALYSIS

Understanding the Mohorovicc discontinuity (Moho depth) is crucial in unraveling the Earth’s subsurface structure. In this research, we present the report of the crustal thickness and the ratio of the primary wave to the shear wave velocities (p-to-s) beneath the seismic station located at the Nigerian Geological Survey Agency (NGSA) Abuja using Receiver Function Analysis (RFA). The primary objective of this study is to determine the depth of the Moho boundary and gain insights into the geological properties of the Earth’s crust and upper mantle beneath the receiver station. This analysis focused on teleseismic earthquakes that were recorded at the station between 2020 and 2021, with epicentere distances between 30o and 90o and magnitudes 5.5 or greater. The P wave Receiver Function (PRF) was modeled from iterative time domain deconvolution using the converted phases (Ps) at the Moho interface.

Crustal imbrication and mountain building in the Eastern Iranian Ranges; Insights from receiver function and Rayleigh wave dispersion analysis

The evolution of the Eastern Iranian Ranges (EIR) dates back to the Late Cretaceous, coinciding with the closure of the Neotethys and the accretion of the Lut Block to Eurasia. However, controversy remains regarding its orogenic processes due to limited knowledge of the lithospheric structure. To gain a better understanding of the tectonic processes and mountain formation in eastern Iran, we analyzed seismic data from 29 stations in the northern part of the EIR. We initially perform receiver function (RF) analyses on 2160 high-quality RFs, emphasizing single-station analysis and Common Conversion Point (CCP) stacking to examine structural variations. Subsequently, we jointly invert the RFs with Rayleigh wave group velocity dispersion curves to derive a shear-wave velocity (Vs) model for each station. Our findings reveal a complex structure with west-dipping interfaces, indicating crustal layering and imbrication. We have identified a significant west-dipping layer, approximately 100 km in length, which could potentially indicate an intra-continental decoupling or shear zone. This decoupling may be responsible for the underthrusting of the Eurasian margin beneath the Lut Block, resulting in a deepening of the Moho depth to over 50 km beneath its footwall, compared to the adjacent Moho depth of around 40 km. Additionally, this process has caused an increase in the topography of approximately 1 km. These findings reflect the potential westward underthrusting of the Eurasian margin. In the deeper parts of the model, we observe a low-velocity anomaly below the crust, shedding light on a weakened lithosphere that facilitates crustal deformation in response to the compressional forces of convergence.

Crustal thicknesses on Thrace Basin via receiver function

The Thrace Basin which is a geological and geographical feature located in southeastern Europe, is the largest and thickest Cenozoic sedimentary basin in Turkey. Various geophysical methods have been used to investigate the basin's properties, tectonic evolution and gain insights into its formation. Within the contexts we applied receiver function method to provide insights on the crustal thicknesses and Vp/Vs ratio beneath Thrace Basin. More than 100 events with magnitudes greater than 6.3 recorded between 2007 and 2022 are evaluated and crustal thickness and Vp/Vs ratio are inferred from H-k analysis. Due to a thick sedimentary fill the average Moho depth is ∼30 km and the average Vp/Vs ratio is ∼1.77 in the Thrace basin which are consistent with the previous studies.

Gravity modelling of the Tyrrhenian-Calabrian-Ionian subduction system

This study provides a lithospheric-scale model along the Ionian Subduction zone in Southern Italy, contributing to the seismotectonic investigation of a region which is affected by relevant historical seismicity. The study employs gravity forward modelling to build the geo-structural model along a composite, NW-SE trending transect extending from the Ionian to the Tyrrhenian Sea, including the Aeolian arc and the Calabro-Peloritan onshore. Through a multidisciplinary approach, we propose new interpretations of three 2D deep-seismic reflection profiles across the study area. Such interpretative profiles are used as constraints to model the observed Bouguer gravity anomalies providing upper and lower crust geometries. Whilst a tomographic model provides constraints for the lithospheric and asthenospheric modelling. The entire workflow is constrained by literature data about Moho geometry, deep seismicity and tomographic images that are integrated to determine the subducting slab geometry. The proposed model of the entire subducting system reasonably fits the observed gravity field and is coherent with the first-order geological and geophysical constraints. The modelling results in updated Tyrrhenian and Ionian Moho depth, subducting slab geometry and location, and densities of the main units, providing valuable input about the composition and geometry of the Calabrian arc structures.

Crustal structure and deformation mechanism of the western northeast Tibetan Plateau

The collision between the Indian and Eurasian plates continues to drive significant deformation and uplift within the interior of the Tibetan Plateau, together with its outward expansion along the margins. In particular, the North Qilian Shan fold-thrust belt (NQLS) and the Hexi Corridor basins (HXBS) represent the northernmost region of the northeastern Tibetan Plateau. This area serves as a natural laboratory for deciphering mechanisms of crustal deformation and thickening along the plateau’s margins. Specifically, the northeastern Tibetan Plateau has been attributed to 1) southward underthrusting of the Asian lithosphere, 2) distributed shortening and crustal thickening, 3) vertical inflation of the Tibetan crust due to mid-lower crustal channel flow, and 4) intracontinental subduction facilitated by large-scale strike–slip faults. The exact mechanism underlying the most concentrated convergent stress in the western segment of NQLS–HXBS remains a subject of debate. To address this uncertainty, we gathered seismic data along a 130-km-long linear array that extends northward from NQLS, traversing the Jiuquan Basin and reaching the Huahai Basin. Our analysis, conducted through the receiver function method, reveals intriguing findings. The Moho depth deepens from 45–50 km beneath the Huahai Basin to 55–60 km beneath NQLS. Notably, a double Moho structure emerged, marked by a distinctive near-flat positive amplitude at a depth of 45–50 km beneath NQLS within a distance of 0–50 km. Our study presents a comprehensive analysis of the crust-scale deformation mechanism, shedding light on the following key aspects: 1) the development of a decollement at 12–20 km depth decoupling the upper and lower crust; 2) deformation of the upper crust occurring through south-dipping brittle thrust faults, while the lower crust features imbricate structures and duplexes; 3) evidence pointing to the underthrusting of the Beishan Block beneath NQLS, indicated by the double Moho beneath NQLS; and 4) the formation of a Moho ramp beneath the Jiuquan Basin, facilitating the transfer of shortening stress from beneath NQLS and HXBS to the north. In the context of the western segment of NQLS and HXBS, our speculation is that coupled distributed shortening and Beishan Block subduction beneath NQLS work in tandem to accommodate crustal deformation.

The crustal structure of the western Amundsen Basin, Arctic Ocean, derived from seismic refraction/wide-angle reflection data

SUMMARY Two geophysical expeditions (LOMROG II and III) were carried out in 2009 and 2012 to acquire seismic data in the western Amundsen Basin in the Arctic Ocean, a basin formed by ultraslow seafloor spreading at the Gakkel Ridge. Previous studies show alternating magmatic and amagmatic segments at the ridge but it is unclear if such segmentation persisted throughout the entire opening history of the basin. The seismic refraction data were used to develop P-wave velocity models down to the uppermost mantle using forward modelling of traveltimes. The coincident seismic reflection data were used to constrain the geometry of the sedimentary layers and for characterizing the acoustic basement. 2-D gravity modelling was used to determine the Moho depth in areas when data quality was insufficient to resolve a Moho reflection. The models distinguish three different basement types: oceanic crust with layers 2 and 3, oceanic crust that is lacking a layer 3 and exhumed and serpentinized mantle. The maximum observed crustal thickness is 6 km. Areas with thin crust (<3 km) may be underlain by partially serpentinized mantle. Where exhumed mantle is observed, a serpentinization front separates highly serpentinized mantle at the top from partially serpentinized mantle below. The presence of oceanic crust off-axis of the presently amagmatic sector of the Gakkel Ridge indicates that there is both a spatial and temporal variation of crustal accretion processes at the ridge.

Radial Anisotropy in Receiver Function H-κ Stacks

Abstract Receiver functions can be used to estimate the Moho depth (H) and ratio of P to S wavespeed (α/β or κ) in the crust. This is commonly done by grid search, forward modeling travel times to produce so-called “H-κ” stacks of receiver function amplitude. However, radial anisotropy in the crust, which can be significant, is almost never considered in this process. Here, we show that radial anisotropy changes the H-κ stack, biasing interpretations of crustal structure by introducing errors up to ∼3% in H and ∼1% in κ for commonly observed anisotropy magnitudes. We propose a simple method to correct H-κ stacks by incorporating radial anisotropy in the forward calculation. Synthetic tests show that this approach almost completely removes error caused by radial anisotropy. We show examples of this procedure with stations in the eastern United States. We provide readers with code to construct radially anisotropic H-κ stacks.

Variations of Crustal Thickness in Alaska and Northwestern Canada: Implications for Crustal Modification and Accretion of Tectonic Units

AbstractThe northwestern part of North America has recorded multiple tectonic events, such as terrane accretion, strike‐slip motion, and subduction of the Pacific and Yakutat plates, providing an iconic setting to investigate the tectonic evolution of the continental crust. In this study we analyze the receiver functions at seismic stations deployed during 1999–2022 to estimate the crustal thickness, as well as possible slab signature, in Alaska and northwestern Canada. The Moho signal can be clearly detected within the continental region. Specifically, in northwestern Canada, the thickest crust is observed beneath the Cordilleran Deformation Front, which marks the structural boundary between the North American Craton and the North American Margin. We observe a few distinct offsets in the Moho depth located both within the tectonic units and approximately across the major faults between the tectonic units. We provide a first‐order estimate of the depth gradient of the Moho offsets based on the horizontal distance of the two closest seismic stations across the offsets. We propose that the Moho offsets reflect the cumulative impact of the accretionary orogenies and post‐orogenic tectonic events on crustal modification. The continental Moho signal is weak or obscure in Aleutian and southcentral Alaska, and the oceanic Moho within the subducting plates is likely detected. This study provides new seismic insights into understanding the impacts of the tectonic events on continental formation and evolution.

Subsidence and Uplift History of the UAE and the Western Flank of the UAE‐Oman Mountain Range

AbstractThe western flank of the UAE‐Oman mountain range offers a unique geodynamic setting to study the development of a cratonic rift into a mature passive margin and its subsequent flexure under orogenic load. However, the geodynamic processes driving this evolution are not fully understood. In this study, seismic and biostratigraphic data from 283 exploration wells were utilized to assess the regional subsidence and uplift history of the United Arab Emirates (UAE) and neighboring areas of the western flank of the UAE‐Oman mountain range. Three major sequences have been identified: pre‐Permian, Permian‐Turonian rifted margin, and Coniacian‐Pleistocene active margin. Backstripping of biostratigraphic data reveals Early Permian (ca. 272 Ma) and Late Jurassic (ca. 160) rift phases, that have been linked to Gondwana's early and final fragmentation. A NE‐SW‐oriented basin in central UAE suggests a Jurassic intracratonic rift that has been influenced by pre‐existing structures. Compressional phases were identified during the Late Cretaceous and in the Oligocene‐Miocene, coinciding with the emplacement of the Semail ophiolite and the Arabian‐Eurasian plates collision, respectively. These events caused additional subsidence and flank uplift, forming the Aruma foreland basin in the east and the Pabdeh foreland basin in the eastern and northern UAE. Crustal thickness following the rift episodes ranges from 30 to 36 km, resulting in a sedimentary cover thickness of 11–14 km. These estimates are in accord with Moho depths derived from teleseismic receiver functions and gravity inversion. These findings can be used to better understand Gondwana fragmentation and the opening and closing of the Neo‐Tethys Ocean.

Crustal structure across the Central part of Narmada-Son Lineament, India based on the interpretation of aeromagnetic and gravity data: Geological implications

Narmada-Son Lineament (NSL) is a prominent geo-tectonic feature located in central India, characterised by complex geological structures and evolution history. In this study, we present a detailed joint interpretation of the aeromagnetic and gravity anomaly maps to delineate the crustal structure in order to address the thermo-tectonic activity below the NSL region. The NW-SE linear trend observed in the aeromagnetic anomaly map correlates well with the major tectonic elements of the NSL and the Vindhyan basin. The low-pass filtered regional gravity anomaly map and corresponding residual anomaly map revealed several crustal-scale structural features in the study area. The Curie depth map of the region prepared from the magnetic anomaly map shows the variation between 24-48 km. The corresponding heat flow map correlates well with the trends in surface heat flow data. The gravity-derived Moho depth map reveals that the values vary between 30-40 km in the NSL region with deeper Moho below the Vindhyan basin. Further, the crustal models obtained from the constrained potential field modelling for two long transects across the NSL in the present study area revealed i) the absence of crustal underplating in the eastern part of NSL below Hirapur-Mandla region, ii) the presence of mid-crustal horst like structure below NSL in both the transects, iii) undulating Moho with higher density crustal rocks within the NSL compared to the surrounding areas. The modelled crustal structure and the analysis of Curie depth as well as heat flow maps of the study area, reveal that the NSL region was affected by repeated tectonic activities since the Proterozoic times, and the present-day tectonics of this belt is greatly influenced by the reactivation of pre-existing faults along the NSL.

Ambient‐Noise Wave‐Equation Tomography of the Alps and Ligurian‐Provence Basin

AbstractTaking benefit of the AlpArray temporary network and permanent networks in W‐Europe, we construct a 3‐D onshore‐offshore velocity model of the crust and upper mantle using ambient‐noise wave‐equation tomography. We use a frequency‐dependent phase traveltime misfit function in an iterative procedure to refine a recent 3‐D Vs model computed from a Bayesian two‐step ambient noise tomography. Observed waveforms consist of vertical‐component noise correlations from 600 broadband stations in the Alps and surroundings, including ocean‐bottom seismometers in the Ligurian sea. We perform 3‐D inversion in the 5–85 s period range. In the long‐period band (20–85 s), an elastic approximation is considered, while in the 5–20 s band, we account for the effect of water layer in the Ligurian sea by applying a fluid‐solid coupling for acoustic‐elastic waveform simulations. The resulting Vs model enhances the shape and contrast of velocity structures, accounting for 3‐D and finite‐frequency effects. It emphasizes the deep sediments of the Ligurian‐Provence basin and focuses on the low‐velocity anomalies of the crust in the W‐Alps. We obtain a high‐resolution Moho depth map covering the Alps and Ligurian sea. In the W‐Alps, this map confirms the deepening of the European crust following the subduction beneath Adria and the existence of major structures such as the Moho jump beneath the external crystalline massifs and shallow depths associated with the Ivrea Body. It provides further constraints on the deep structure beneath the Ligurian‐Provence basin, regarding the lateral and along‐strike crustal‐thickness variations from the oceanic domain to the conjugate margins.

Tithonian mafic intrusions in north-central Newfoundland: link to Atlantic rifting?

The small volume, Mesozoic alkali gabbro intrusions of the Budgell Harbour and Dildo Pond stocks and associated alkaline lamprophyre dykes in Notre Dame Bay in Newfoundland are an example of onshore magmatism that may be associated with North Atlantic Ocean opening. Chemical abrasion isotope dilution thermal ionization mass spectrometry U–Pb dating of zircon from Budgell Harbour Stock drill core samples yielded a weighted average 206Pb/238U age of 147.9 ± 0.5 Ma (95% confidence interval, mean square weighted deviation = 0.10). Five 40Ar/39Ar laser step-heating, single phlogopite grain analyses from the Budgell Harbour and Dildo Pond stocks, plus a lamprophyre dyke, yielded ages ranging from 146.3 ± 0.2 to 149.5 ± 0.5 Ma. The data demonstrate a ca. 148 Ma (Jurassic and Tithonian) alkaline magmatic event in Newfoundland, contemporaneous with rifting and offshore basin formation. These new age data and published determinations from magmatic rocks on conjugate margins and adjacent regions reveal long-lived episodic magmatism in the embryonic North Atlantic rift environment. We propose a new model whereby magmatism occurred in Notre Dame Bay at the convergence of older crustal-scale faults and localized Moho depth variations that may have triggered lithospheric mantle melting through isothermal, distal, and edge-driven upwelling related to regional extension.

Moho Inversion by Gravity Anomalies in the South China Sea: Updates and Improved Iteration of the Parker‐Oldenburg Algorithm

AbstractThe Moho is the interface between crust and mantle, and accurate location of the Moho is important for both resource exploration and deep earth condition and structural change investigations. The theory of the traditional Parker‐Oldenburg (P‐O) method is quite simple and it is widely applied in the frequency domain of Moho depth inversion. However, Moho fluctuation simulations using the P‐O method are not reliable because of the lack of field geographic data constraints during the inversion process and the excessively smoothing of data details caused by using filters to correct the source data signals. To solve those problems, we propose an improved iteration P‐O method with a variable density contrast model, the iterative process is constrained by geological data in the inversion parameters, and the variable depth of the gravity interface is iterated using an equivalent form of upward continuation in the Fourier domain, which is more stable and convergent than downward continuation term in original P‐O method. Synthetic experiments indicate that improved method has the better consistency among the simulations than original method, and our improved method has the smallest root mean square (RMS) of 0.59 km. In a real case, we employed the improved method to invert for the Moho depth of the South China Sea (SCS), and the RMS between our Moho depth model and the seismological data is the smallest value of 2.27 km. The synthetic experiments and application of the model to the SCS further prove that our method is practical and efficient.

A High‐Resolution Shear Velocity Model of the Crust and Uppermost Mantle Beneath Westernmost Mediterranean Including Radial Anisotropy

AbstractUsing seismic data from 1,186 stations deployed across the westernmost Mediterranean, we construct a high‐resolution 3‐D radially anisotropic model from a joint inversion of receiver functions and Rayleigh and Love wave dispersions. The Rayleigh and Love data are extracted from both ambient noise interferograms and earthquake waveforms, and a new three‐station ambient noise interferometry method is used to further improve the data coverage. The obtained crustal thickness map reproduces independently the Moho depth maps compiled from previous data, showing crustal roots beneath the Pyrenean‐Cantabrian range and the Gibraltar Arc and thicker crust beneath the Variscan Iberian Massif than in the area affected by Alpine orogenesis. The Vsv crustal model outlines the Iberian Massif as a high shear wave velocity block and shows extremely low velocities in the Gulf of Cadiz and Gibraltar Arc. At mantle levels, a sharp boundary between the Aquitanean Basin and the Massif Central is imaged, with low Vsv beneath the Massif Central probably reflecting a remaining signature of the magma. To the south of Iberia, the geometry of the Alboran slab is captured by the model, while beneath the Atlas Mountains, widespread low Vsv and positive radial anisotropy is observed, favoring the edge‐driven convection model explaining the lithospheric thinning. The most relevant contribution of this work is mapping, for the first time at this scale, the radial anisotropy anomalies at crustal level, with higher values observed in the Alpine Iberia, dominated by present‐day extensional tectonics.

Imaging of crustal structure beneath the Larsemann Hills, Antarctica using scattered wave technique – First Results

The crustal structure in terms of crustal thickness, shear wave velocities and Poisson's ratio plays a crucial role in understanding and/or deciphering the tectonic setting and its evolution. The receiver function analysis, H–K stacking and inversion techniques are the widely used tools to determine these parameters. In the present study, the data obtained from the first-ever established broadband seismological observatory at Larsemann Hills, East Antarctica has been utilized for the P receiver function (PRF) analysis and H–K stacking to decipher the crustal thickness, Poisson's ratio and the intra-crustal layer. Further, the obtained PRFs were inverted using Bayesian inversion to get the crustal structure. The results obtained from H–K analysis reveal a crustal thickness of ∼37.9 km and the corresponding Poisson's ratio is 0.19. The inversion technique also yielded consistent results, indicating a Moho depth of ∼37 km with a velocity jump from 4.1 km/s to 4.6 km/s and an intra-crustal layer at around 16 km with a velocity jump from 3.95 km/s to 4.06 km/s. It indicates a Poisson's ratio of 0.20. These findings suggest that the crust beneath the Larsemann Hills is felsic in nature and has high crustal shear wave velocity. Further, the variation in the crustal thickness along the coast of the Princess Elizabeth Land (PEL) region, ranging from 37.9 km to 36 km with the intra-crustal layer variation from 16 km to 13 km distinguishes the Neoproterozoic Larsemann Hills from the Archean-Mesoproterozoic Vestfold Hills.

Moho depth estimation of northern of East African Rift System

Abstract The northern part of the East African Rift System is characterized by depleted Moho depth and thermally thinned lithosphere. This research aims to determine the Moho depth of the study area through non-linear gravity inversion and cross-validation with seismic Moho estimates. The study utilized gravity data to obtain the gravity anomaly of the Moho interface, a topographic grid for removing topographic effects, a crustal model to determine total sediment thickness and its gravitational effect, and seismic Moho depth for constraining the forward model and cross-validation. The estimated Moho depth of the study area ranges between 5 km (in the Indian Ocean) to 45 km (in the Ethiopian Highlands), with slight variation compared to seismic Moho relief. This is because the reference level, calculated for the thinner part of the study region, underestimates the entire area. Upwelling magma in the Eastern branches of the EARS may also incur slight variation in the estimated Moho depth; rifting, volcanism, melt intrusion, magmatic uplift, and tectonic setting all influence the Moho depth of the study area. Furthermore, reverberations affect most seismic Moho estimations in the region. The slight variation can be mitigated by improving the gravity network for accurate validation and precise heat flow measurement to correctly identify magmatic anomalies and density contrasts. Additionally, applying reverberation removal techniques in the study region could improve seismic Moho estimation.