This paper aims at providing an accessible introduction to ultracold quantum gravimeters tailored for geophysicists. We do not focus here on geophysical applications, as these are already well known to geophysicists, but rather provide a pedagogical exposition of the quantum-mechanical concepts needed to understand the operation of quantum gravimeters. We present a review of gravimeters based on two- and three-level atomic systems, focusing on the fundamental mechanisms of atomic interferometry. The functioning of Mach-Zehnder interferometers is discussed through the action of π/2 and π pulses, showing how the resulting phase shift encodes gravitational acceleration. The effect of noise is briefly discussed.

Cornwall Peninsula is an extended region in the southwest of Great Britain, characterized by the presence of an early Permian granitic body, the Cornubian Batholith, emplaced at the end of the Variscan orogeny. It is composed of six major plutons, intruded into a metasedimentary matrix of Devonian and Carboniferous rocks. The batholith has a rich mining history dating back to the prehistoric period, with ore fields associated with various stages of its emplacement. Active mines, primarily focused on kaolin extraction, also show potential for the production of tin, lithium, and tungsten, as well as the exploitation of geothermal energy. This makes the area attractive from an economic point of view. We propose a new and enhanced 3D model of the Cornubian Batholith, derived from a joint inversion of gravity and magnetic datasets. By integrating petrophysical constraints from granite samples with a regional density model, we isolate the geometry of the crustal body. Batholith reaches a maximum depth of 12 km beneath the Dartmoor pluton, suggesting that the low density of the granites provide an isostatic compensation. We also estimated the total volume and mass of the Batholith, reaching, respectively, 34,283 km3 and 9.096 × 1016 kg. Magnetic anomalies indicated two minor zones of interest, including a magnetized area within the Lizard Complex. Our results contribute a detailed crustal model that refines the understanding of the batholith’s structure, mineral potential, and geodynamic context.

Gravity forward modeling, based on Newton’s law of gravitation, describes the relationship between subsurface mass density distribution and observed gravity data. It has broad applications in global geodynamics, resource exploration, and planetary sciences. The tesseroid (spherical prism) is widely used to represent mass density elements on a spherical Earth, but its application is hindered by singularities, numerical instabilities near computation points, and the trade-off between accuracy and efficiency in large-scale modeling. To address these theoretical deficiencies, we propose a novel tesseroid gravity forward modeling algorithm formulated in the spherical harmonic domain. The spherical harmonic coefficients are separated into three parts: (1) an analytical, non-singular expression in the radial direction; (2) an analytical, non-singular expression in the longitudinal direction; and (3) a latitudinal integral, efficiently evaluated without singularities using the Gauss–Legendre quadrature (GLQ). Fast Fourier transform (FFT) technique is combined with spherical harmonic synthesis to further enhance computational efficiency. Validation with spherical shell tests shows that accuracy depends jointly on the spherical harmonic expansion degree and the GLQ order, meaning that higher expansion degrees require more GLQ nodes, while greater computation heights reduce the required order. For a single tesseroid, the proposed method matches the adaptive discretization method in both spatial distribution and magnitude of gravity disturbances, with mean differences below 1 mGal, while reducing computation time by 35

We investigate the relationship between Bouguer disturbance and equivalent topography across Antarctica using satellite gravity data, under the assumption that a linear relationship is expected at long wavelengths for Airy-type isostatic compensation. Equivalent topography ensures consistency across continental, marine, and ice-covered domains by expressing bathymetry and ice loads as crustal-equivalent height. The analysis is based on the GOCO06S satellite-only gravity model and BedMachine v3 datasets. Bouguer disturbance is computed through forward modelling of all relevant mass contributions using prism integration. Spatial variations in the gravity–topography relationship are quantified using moving circular windows (264 km diameter, 75% overlap), consistent with the effective resolution of the gravity model and the wavelengths at which local compensation is expected. For each window, slope, intercept, correlation coefficient (r), coefficient of determination (R²), and RMSE are estimated. Regions such as the Antarctic Peninsula and the southern Transantarctic Mountains exhibit high R² and strong negative correlation, indicating a coherent long-wavelength coupling between gravity and topography. While consistent with Airy-type compensation, this behaviour may also reflect contributions from mantle density variations associated with thermal anomalies. In contrast, large sectors of East Antarctica show positive correlation and low to moderate R² values. Combined with seismic evidence for thick and cold lithosphere, this pattern indicates that gravity variations are influenced by lithospheric rigidity and regional compensation rather than local Airy-type crustal thickening. The joint interpretation of regression parameters further delineates candidate subglacial sedimentary basins, in agreement with independent probabilistic models, and identifies new regions of interest for future geophysical investigation.

Ocean tidal loading (OTL) induced surface displacements, driven by lunar and solar gravitational forces, present significant challenges in geodetic applications, requiring precise modeling to improve GNSS positioning accuracy. The study conducts a methodological and feasibility assessment of the differential and absolute approaches for detecting and quantifying OTL signals from GNSS coordinate time series. By analyzing GNSS data from selected stations, this research assesses the strengths and limitations of DD and PPP in estimating OTL displacements. Applying the OTL model correction reduced coordinate RMS values by up to 22 K_1 . However, diurnal constituents are particularly sensitive to GNSS-related systematic effects, including satellite orbit mismodelling and constellation repeat periods. Long baselines in DD improved detectability of differential signals but can introduce residual atmospheric biases, whereas shorter baselines were more resilient to noise yet less sensitive to weak tidal components. These results demonstrate that millimeter-level OTL displacements can be reliably detected with GNSS, but the choice of processing strategy and baseline configuration strongly influences the accuracy, resolution, and spectral completeness of the recovered tidal signals. By quantifying these effects across contrasting tidal regimes, this study provides a rigorous assessment framework that can guide the optimal use of DD and PPP in geodetic and geophysical applications.

The northern Adriatic Sea provides an exceptional setting for investigating tidal processes because of its shallow bathymetry, elongated basin geometry and semi-enclosed configuration. These characteristics produce some of the largest tidal amplitudes in the Mediterranean and favour the amplification of both diurnal and semidiurnal constituents, leading to complex sea level variability and episodic extreme events such as high stands along the coastal cities. We analyse tidal dynamics and ocean tidal loading (OTL) in the northern Adriatic using a multitechnique approach that combines tide gauge (TG) observations, interferometric reflectometry (GNSS-IR) sea level retrievals and Global Navigation Satellite System (GNSS) precise point positioning (PPP) solutions describing crustal deformation. Tide gauge records confirm the progressive increase of semidiurnal tidal energy towards the northern end of the basin, with the $M_2$ and $S_2$ constituents dominating over the diurnal band. These observations broadly agree with the FES2014b ocean tide model, although local amplitude and phase deviations are observed in shallow and geometrically complex coastal environments. Sea level time-series derived from GNSS-IR at several coastal sites show a high degree of agreement with nearby tide gauges, with correlations exceeding 90 per cent. Both diurnal and semidiurnal constituents are well resolved, and amplitude differences remain within 4-5 cm, demonstrating the potential of GNSS-IR as an effective and low-cost complement to traditional TG networks. GNSS PPP solutions further allow the estimation of 3-D OTL displacements at hourly temporal resolution. The vertical component is primarily controlled by the semidiurnal $M_2$ tide and closely matches model predictions in both amplitude and phase. Larger discrepancies are observed for diurnal constituents, particularly $K_1$, likely related to interactions with GNSS orbital periods and remaining systematic effects in the processing. Overall, this work presents the first high-temporal-resolution GNSS-based assessment of ocean tidal loading in the northern Adriatic. The strong consistency among GNSS, GNSS-IR and TG observations highlights the capability of integrated GNSS approaches to simultaneously capture oceanographic variability and solid Earth tidal deformation, opening new perspectives for coastal sea level monitoring, geodetic stability studies and hazard assessment in a changing climate.

Based on gravity anomalies, magnetic anomalies, and surface heat flow data from the South China Sea (SCS) and adjacent regions, this study applies a Curie point depth–constrained thermal modeling approach to construct regional-scale, spatially continuous models of lithospheric thermal structure and effective elastic thickness (Te) within a unified framework for the first time. Integrated analysis of the thermal models and four representative geophysical profiles (P1–P4) systematically reveals spatial variations in lithospheric thermo-mechanical structure and their tectonic controls. The results show that Te generally correlates positively with lithospheric thermal thickness at the regional scale, but exhibits pronounced variations among different tectonic settings, with local deviations influenced by lithology, tectonic stress, and evolutionary history. The central ocean basin and sub-basins are characterized by extremely thin thermal lithosphere and low Te, reflecting thermally controlled lithospheric weakening associated with seafloor spreading and mantle heat input. In contrast, the northern passive continental margin and southern compressional domains display cold, thick lithosphere and relatively high Te, primarily controlled by long-term post-rift cooling and enhanced deep mechanical coupling. The Manila subduction zone and its forearc show the lowest Te values, indicating mechanically dominated weakening related to stress concentration and slab bending, with thermal anomalies playing a secondary role. Overall, the lithospheric thermo-mechanical structure of the SCS and surrounding regions exhibits strong lateral heterogeneity, controlled by the combined effects of seafloor spreading, mantle heat supply, margin compression, and plate subduction. Through multi-parameter joint constraints and tectonic partitioning, this study identifies the dominant controls on Te across different tectonic units, providing new regional-scale geophysical constraints on the thermo-mechanical evolution of the SCS lithosphere and on marginal-sea geodynamics.

This study integrates airborne magnetic and radiometric data to characterize anomalies linked to concealed structural features and magmatic rocks from Triassic, Jurassic-Cretaceous and Eocene periods in the central High Atlas domain of Morocco, with a special focus on the Tamazert alkaline‑carbonatite complex. Advanced processing of magnetic data revealed networks of lineaments oriented mainly ENE-WSW to NE-SW, correlating with major regional faults. Three-dimensional Euler deconvolution indicates pipe-like magmatic intrusions with magnetic sources at depths reaching 3000 m. The oval-shaped Tamazert complex extending from southwest to northeast, consists of a mixture of highly magnetic lithologies hosted in low-magnetization Liassic limestone rocks. Its three-dimensional magnetic inversion reveals four isolated, elongated bodies oriented northeast and consisting of highly magnetic (above 0.023 SI) rocks that become homogeneous at depth toward the deepest main body, reaching 4850 m. Radiometric analysis delineates the prominent NE-trending structural corridor featuring high radioelements contents, spatially associated with syenite, foid-syenite, malignite, monzonite and carbonatitic breccias, and sharply contrasting with low-radioelements country rocks. The highest enrichment is located in specific sectors near Tafraout and Issali Igban localities. The sigmoid shape of the NE-trending complex is emplaced within a pull-apart structure controlled by reactivated sinistral strike-slip faults interpreted as a far-field response to the convergence between Africa and Europe. This tectonic regime generated localized extensional zones that promoted magma ascent and emplacement. These findings enhance the understanding of the region's subsurface geology.

Abstract. The ESA SING project evaluates the added value of the Next Generation Gravity Mission (NGGM) and the Mass-change and Geoscience International Constellation (MAGIC) for scientific applications and operational services in hydrology, oceanography, glaciology, climate science, solid Earth science, and geodesy. Using a closed-loop simulation framework that incorporates realistic instrumental, tidal and aliasing errors, synthetic gravity observations were generated to assess the capability of future satellite gravity missions to monitor mass variations in the atmosphere, oceans, hydrosphere, cryosphere, and solid Earth. The enhanced spatial and temporal resolution of NGGM and MAGIC substantially improves the monitoring and prediction of hydrological extremes, including floods and droughts, while estimates of total water storage anomalies, combined with complementary in situ observations and hydrological models, enable improved estimation of key variables of the continental water cycle, including precipitation and total drainable water storage. The improved resolution, accuracy, and temporal coverage of gravity observations are also critical for detecting climate-driven changes in the Atlantic Meridional Overturning Circulation (AMOC). Enhanced monitoring of mass changes in glaciers and ice sheets enable the detection of more rapid melt and accumulation events at finer spatial scales. Improved closure of sea-level and energy budgets is achieved through more accurate observations of mass redistribution at smaller spatial and temporal scales. In solid Earth applications, NGGM and MAGIC increase sensitivity to co-seismic and post-seismic deformation associated with smaller earthquakes while reducing data latency, thereby strengthening geohazard assessment and early warning capabilities. In geodesy, the missions support improved gravity field and geoid modelling, contributing to the realization and temporal evolution of the International Height Reference Frame (IHRF) and to more accurate precise orbit determination. Overall, the ESA SING results provide strong evidence of the scientific and societal benefits of NGGM and MAGIC to prepare the integration of future Earth Observation data into operational services.

The southern Kamchatka Peninsula lies along the southeastern margin of the Okhotsk microplate; a region identified with high seismic potential. This segment of the megathrust hosted the historic Great Kamchatka earthquake (Mw = 9.0) in 1952, one of the four largest ever instrumentally recorded. On July 29, 2025, an Mw = 8.8 earthquake ruptured a similar portion of the megathrust through shallow reverse faulting, which is characteristic of subduction zones. In this study, we investigate the coseismic slip behavior of this event along the Kuril-Kamchatka subduction zone by directly modeling gravity data from the GOCE satellite mission. Finite-fault models from different data sources indicate that the rupture propagated entirely southwestward. Most of these models showed that deformation was distributed across distinct patches, with the highest slip occurring to the southwest of the epicenter, mainly between 50° and 51° N, coinciding with a low anomaly of the vertical gravity gradient (Tzz). Spectral coherency between a coseismic slip distribution model and Tzz showed a correlation of about 90%. A saddle-point in the Tzz variation at 53° N marks an important seismic barrier that also constrained previous great megathrust earthquakes. The northeastern termination of foreshock and aftershock activity further supports this. Another seismic barrier was inferred at 51° N by comparing Tzz to coseismic slip and to kinematic rupture models. Our results show that the Tzz effectively maps major asperities and barriers, in agreement to the degree of interseimic coupling, as found in previous studies of other great megathrust events around the world. We conclude that the density distribution mapped from satellite GOCE indicates a primary factor controlling seismic segmentation. We also propose the Tzz as a first-order proxy for seismic hazard assessment, as well as for constraining locking and finite-fault models that require a priori information on megathrust structure.

Continental convergence of Indian and Eurasian plates produces Himalayas in the north, while tectonically complex transpressional zones of the Sulaiman Fold and Thrust (SFT), and Kirthar Fold and Thrust (KFT) belts in the East. Seismic hazards in the zones are very high and less understood due to complex tectonic settings, and lack of GPS network. Here, we take advantage of spaceborne SAR interferometry and use the Sentinel-1, and ALOS-2 ScanSAR satellite observations to estimate the coseismic deformation caused by the 2021 Mw 6.0 Harnai earthquake in the western zone of the SFT belt. We find the line-of-sight (LOS) displacement of ~80 and ~70 mm from Sentinel-1 descending and ascending interferograms respectively. We find the ~50 mm of LOS displacement from ALOS-2 descending interferogram, but it is majorly biased by lower and upper atmospheric noises even after the GACOS and ionosphere corrections. In order to avoid the major noise components in inversions that may affect the accuracy, we discarded the ALOS-2 LOS displacement and relied only on the ascending and descending interferograms of Sentinel-1data. The deformation has an oblique component, but mostly dominated by thrusting on the NW-SE trending Harnai fault. First, we invert the LOS displacement using geodetic Bayesian Inversions approach, and find two plausible fault plane the NW-SE trending, and the NE-SW trending solutions. The simplified fault parameters have a strike of 327° ± 12, a dip of 31° ± 9, the length of 8.3 ± 2.1 km, and the width of 2.5 ± 2.0 km, which fits well the ISC and USGS fault models. Then, we determine the finite slip distributions on both plausible faults. The NW-SE trending fault shows the maximum slip is found to be 70 cm at around 8 km depth. The slip distribution along the down dip and strike of the fault shows that 85% of the slip is concentrated in an area of (9 × 9) = 81 km2 at a down dip distance of 3 - 12 km. Furthermore, the results show the earthquake is propagated equally along strike and dip. For the NE-SW trending fault the maximum slip is similar but has higher residuals and scattered slip along depth. Therefeore, we preferred the NW-SE trending fault plane solution because based on the compatibility with fault structures in the region, and higher accuracy in the inversions. We also determine postseismic movement using time series analysis of spaceborne Sentinel-1 SAR data, but no significant afterslip and viscoelastic relaxation signals is found on the fault after the earthquake.

Small-scale lithospheric terranes (microplates) are important building-blocks of continental accretion but their presence is often obscured by subsequent plate-margin deformation events and by younger volcano-sedimentary covers. The geological fabric of the eastern Anatolian-Caucasian region results from the sequential accretion of lithospheric terranes against the southwestern continental margin of the Eurasian plate. Widespread sedimentary and volcanic covers conceal some of the principal tectonic boundaries in the region, and major uncertainties persist as to the number and extent of the various terranes. We determine whether the topographic height fits the expectance from crustal thickness, complying to the isostatic equilibrium. The input data of the study are the topography, the satellite derived gravity field, the geologic knowledge defining magmatic intrusions and tectonic terranes, arcs and sedimentary basins, the seismic Moho depth, and a seismic tomography model. We accomplish a topography-gravity regression analysis controlled by a seismic Moho model, which produces well defined positive and negative anomalies. Allowing for varying density contrast in lower crust, the topography is greatly in isostatic equilibrium and controlled by the crustal thickness, that is topographic uplift has evolved proportionally to crustal thickening. The average density contrast in lower crust is between 200 and 300 kg/m3 for the orogenic belt, with local exceptions. The inversion of the prominent positive linear anomalies of the regional gravity field defines discrete crustal density inhomogeneities, which can be interpreted as related to specific tectonic events, thus placing cogent constraints on the accretionary history and the overall anatomy of the eastern Anatolian-Caucasian lithospheric agglomerate. Three linear belts of intracrustal increased density are found along (i) the Greater Caucasus, (ii) the Lesser Caucasus, and (iii) a previously unidentified parallel belt ca. 80 km south of the Lesser Caucasus. The latter gravity anomaly clearly delineates for the first time the southwestern margin of the South Armenian Block, a lithospheric element (microplate) whose existence has long been a matter of debate. (c) 2024 China University of Geosciences (Beijing) and Peking University. Published by Elsevier B.V. on behalf of China University of Geosciences (Beijing). This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

The basins composing the 1000-km wide West Antarctica Rift System (WARS), derived from extensional dynamics lasting from the Cretaceous to the Middle Neogene, bear evidence of a peculiar evolution through time: a transition from a diffuse to a localized thinning style and a migration of the focus of deformation, which likely progressed towards the cratonic domains of West Antarctica. Using the current observations, we aim at identifying which inherited starting conditions [1] result in outcomes compatible with the present-time structures and which do not allow so, unless other factors are accounted for. To this aim, we turn to an extensive grid search in the parameter space, running a large number of forward numerical models to cover the possible permutations of parameters under test. We use the open source Underworld2 code [2] with a simplified scheme of starting conditions and kinematics boundaries, for lithospheric-scale 2-D thermomechanical models. We analyse the results obtained by changing a great number of parameters, including initial geometries of the crust and lithosphere, different rheologies, inherited structures, such as strain-weakening scars and thermal remnants of slabs. We identify that a high crustal thickness (more than 45 km) is required to accommodate the first rifting phase (170 km ca. of cumulated extension, [3]) without producing crustal necking and eventual ocean formation. Parameters that favour a weaker strength profile, chiefly temperature (due to a thicker crust and/or a shallow lithosphere-asthenosphere boundary), are also required to avoid an early transition to localized deformation, in agreement with previous studies [4]. Smaller scale features, such as partition in multiple sub-basins, require additional factors, such as inherited weak-zone seeds (“scars”) in the crust and mantle, which are likely remnants of previous compressive phases [5]. [1] Perron, P., Le Pourhiet, L., Guiraud, M., Vennin, E., Moretti, I., Portier, É., & Konaté, M. (2021). Control of inherited accreted lithospheric heterogeneity on the architecture and the low, long-term subsidence rate of intracratonic basins. BSGF - Earth Sciences Bulletin, 192. https://doi.org/10.1051/bsgf/2020038 [2] Mansour, J., Giordani, J., Moresi, L., Beucher, R., Kaluza, O., Velic, M., Farrington, R., Quenette, S., & Beall, A. (2020). Underworld2: Python Geodynamics Modelling for Desktop, HPC and Cloud. Journal of Open Source Software, 5(47), 1797. https://doi.org/10.21105/joss.01797 [3] Brancolini, G., Busetti, M., Coren, F., De Cillia, C., Marchetti, M., De Santis, L., Zanolla, C., Cooper, A.K., Cochrane, G.R., Zayatz, I., Belyaev, V., Knyazev, M., Vinnikovskaya, O., Davey, F.J., Hinz, K., 1995. ANTOSTRAT Project, seismic stratigraphic atlas of the Ross Sea, Antarctica. In: Cooper, A.K., Barker, P.F., Brancolini, G., (Eds.), Geology and Seismic Stratigraphy of the Antarctic Margin. Antarctic Research Series, vol. 68, https://doi.org/10.1029/AR068 [4] Huerta, A. D., & Harry, D. L. (2007). The transition from diffuse to focused extension: Modeled evolution of the West Antarctic Rift system. Earth and Planetary Science Letters, 255(1–2), 133–147. https://doi.org/10.1016/j.epsl.2006.12.011 [5] Talarico, F., Ghezzo, C., & Kleinschmidt, G. (2022). The Antarctic Continent in Gondwana: a perspective from the Ross Embayment and Potential Research Targets for Future Investigations. In Antarctic Climate Evolution (pp. 219–296). Elsevier. https://doi.org/10.1016/B978-0-12-819109-5.00004-9

The upcoming gravity missions anticipated in the next decade are expected to significantly reduce noise levels compared to current data acquisitions from GRACE and GRACE Follow On. Our objective is to proactively prepare for these future datasets and develop scientific processing tools that can yield innovative applications in solid earth research. These applications have the potential to evolve into community-relevant ser-vices for earth monitoring and exploration.We specifically focus on key categories such as earthquakes, crustal uplift and subsidence, seamounts, and lithospheric structure. Accurately estimating the gravity field necessitates the formulation of realistic 3D models of density and their temporal changes.Uplift and subsidence is considered for the Alpine mountain arc, where a lithosphere density model has been formulated (Tadiello & Braitenberg, 2021) imposing vertical movements from measured GNSS rates. The exploration of the lithosphere is tested on a recent 3D density model of Iran (Maurizio et al., 2023) which was inverted from the presently available gravity field integrated with a seismic tomography model. We distinguish crustal and mantle signals and evaluate prospective improvements to detect structures in crust and mantle.In the context of earthquakes, our focus lies in improving the minimum detectable magnitude, depending on fault plane mechanisms, and detecting post-seismic relaxation. Seamounts pose a unique challenge with limited alternatives for detection, placing gravity detection in a primary role, provided the associated mass changes are sufficiently significant. Therefore, we conduct a review of documented seamount eruptions, estimating the associated mass changes. Particularly intriguing are 'silent' seamounts that grow several hundred meters high without breaking the ocean surface, remaining invisible.We compare the signals against noise levels of the future gravity missions, including the polar and inclined satellite couples with inter satellite distance measurement, the MAGIC proposal (Daras et al., 2024) and proposals with the payload of quantum technology gradiometers presently under discussion at ESA and NASA. ReferencesDaras, I., March, G., Pail, R., Hughes, C. W., Braitenberg, C., Güntner, A., Eicker, A., Wouters, B., Heller-Kaikov, B., Pivetta, T., & Pastorutti, A. (2024). Mass-change And Geosciences International Constellation (MAGIC) expected impact on science and applications. Geophysical Journal International, 236(3), 1288–1308. https://doi.org/10.1093/gji/ggad472Maurizio, G., Braitenberg, C., Sampietro, D., & Capponi, M. (2023). A New Lithospheric Density and Magnetic Susceptibility Model of Iran, Starting From High‐Resolution Seismic Tomography. Journal of Geophysical Research: Solid Earth, 128(12), e2023JB027383. https://doi.org/10.1029/2023JB027383Tadiello, D., & Braitenberg, C. (2021). Gravity modeling of the Alpine lithosphere affected by magmatism based on seismic tomography. Solid Earth, 12(2), 539–561. https://doi.org/10.5194/se-12-539-202

The South China Sea (SCS) and its adjacent regions lie at the junction of the Eurasian, Pacific, and Indian plates, characterized by complex tectonic evolution and diverse lithospheric features. This study integrates magnetic anomaly, gravity, and heat flow data to investigate the lithospheric thermal structure, effective elastic thickness (Te) distribution, and dynamic processes in the region. Curie depth was constrained using EMAG2 magnetic anomaly data with traditional and improved centroid methods, and the lithospheric thermal structure was calculated using the steady-state heat conduction equation. Te was derived from the fan wavelet coherence method based on WGM2012 gravity data, topographic data, and Moho depth models, providing a comprehensive understanding of the thermal and mechanical properties of different tectonic units.The results reveal that the lithosphere in the SCS basin is thin (40–50 km) with high geothermal gradients and heat flow, resulting in low thermal and mechanical strength and Te values of 10–15 km, indicative of young oceanic lithosphere. In contrast, the northern continental margins exhibit thicker lithosphere (>80 km) with lower heat flow and higher rigidity, reflected in Te values of 25–35 km, which align with craton stability and compressional forces from the Eurasian plate. Transitional crustal regions, such as the Xisha and Nansha Islands, exhibit intermediate lithospheric thickness (50–70 km), geothermal gradients, and Te values (10–20 km), representing a transition between oceanic and continental lithosphere. The subduction zones, such as the Manila Trench, display combined characteristics of lithospheric bending and mantle wedge thermal anomalies, with outer trench regions showing Te values of 15–25 km, while forearc regions exhibit significant weakening with reduced Te.Dynamic analysis suggests that the diverse lithospheric thermal structure and Te distribution in the SCS reflect the combined effects of seafloor spreading, subduction, and extensional deformation. High temperatures and thin lithosphere in the basin support its extensional setting; low-temperature, high-Te features of continental margins indicate compressional deformation; transitional crust reflects dual controls from continental extension and oceanic spreading; and subduction zones demonstrate complex mechanical interactions, including lithospheric bending, compressional stresses, and mantle upwelling, which significantly impact lithospheric dynamics.This study provides new insights into the thermomechanical and dynamic evolution of the lithosphere in the SCS and adjacent regions, offering a robust framework for regional tectonic and geophysical research.

We evaluate simulations for single-, double- and multiple-pair satellite gravimetry missions with respect to applications in hydrology, sea level budgeting, and solid Earth science. We begin with the retrieval of weekly spherical harmonic solutions from GRACE-FO and MAGIC-like inter-satellite laser tracking in the presence of realistic aliasing, as well as from more distant scenarios that would involve flying quantum accelerometers on satellite pairs in various orbital planes of different inclination. To account for realistic applications, we simulate the impact of such data products in basin-averaged total water storage recovery, in the retrieval of water storages via assimilation into global and regional models, in global and regional ocean mass estimation also in combination with radar altimetry, and in the monitoring of Earthquakes and submarine volcano growth. While we find that the MAGIC simulation provides the largest improvement step with respect to our GRACE-FO simulation, the more advanced scenarios add sensitivity in particular in applications where gravity and mass change data can be directly equated to observable phenomena. It is more challenging to judge the benefit of advanced missions with scientific applications that involve combination with model ensembles and additional remote sensing data, as their uncertainties may determine the noise floor and will need to be projected into the future, which we did not attempt at here.

The substantial improvement in spatio-temporal accuracy that will be provided by the ESA NGGM/MAGIC mission will make it possible to take a decisive step forward in our knowledge of the dynamics of the main physical processes involving the different compartments of the Earth.Since every physical process that occurs within each terrestrial compartment involves a redistribution of mass and therefore a signal of gravity, the project intends to provide results of impact and breakthroughs in the modeling and understanding of the dynamics of Solid Earth and Fluid Earth processes, the latter including the water stored in continents and oceans, as well as in geodesy.Methodologies will be developed that link gravity signals from the various compartments of the Earth to the MAGIC raw data, finally linking each terrestrial compartment with the two pairs of satellites, the core of MAGIC.The partnership proposing the project includes researchers from different Universities and Research Institutions and has all the skills in the various sectors mentioned above, from its assets in basic science to the application ones.The following activities are planned:- Modeling of the gravitational effects of slow tectonics and seismic cycle- Modeling of the gravitational effects from volcanic processes- Development of methodologies of compact imaging/inversion for the estimation of mass changes- Tidal and ocean circulation models for gravity signal and generation of L2 data- Precipitation and river flow models, hydrological models for the TWSA- High resolution background gravity and gravity anomaly error determination and E2E simulations for geophysical processes detectability.Among the objectives of these activities, common to all partners, there will be in particular that of verifying that the spatio-temporal resolution of MAGIC allows to satisfy the requirements necessary to extract from the mission data the gravity signal that allows a significant advance in the basic research and related applications in the various geophysical and geodetic components.The project is funded by the Italian Space Agency - ASI.

Since 2002, the GRACE and GRACE-FO satellite gravity missions have been observing changes in the Earth’s gravity field. ESA and NASA are currently planning a double-pair satellite constellation MAGIC, which promises an enhanced spatial and temporal resolution compared to GRACE/-FO. After MAGIC, in the long-term post-2040-time frame, a gravity mission constellation with multiple satellite pairs equipped with novel quantum sensor instrumentation is considered as a promising candidate concept to improve the observation time series even further. It has the potential to acquire unprecedented data on key Earth processes and is expected to significantly expand the potential range of applications. Within the ongoing ESA project “Quantum Space Gravimetry for monitoring Earth’s Mass Transport Processes” (QSG4EMT) an online questionnaire was created to assess user requirements for such a future quantum mission concept. We will present the results of this community assessment based on 135 answers from various user groups (hydrology, oceanography, glaciology, atmospheric and climate sciences, solid earth sciences, and geodesy). In addition to application-driven demands of the different disciplines regarding the required spatial and temporal resolution, accuracy, and latency, we discuss the expected added benefits of hypothetical future mission scenarios and outline possible new application fields.

Co-seismic dislocation and post-seismic relaxation are mass transport processes that can be sensed by a broad array of seismological and/or geodetic techniques. Gravity observations through time have the potential of improving the amount of available information on these processes, especially when the dislocation is a-seismic and when its surface expression occurs mostly in areas that are difficult or impossible to sense with space geodesy (such as GNSS, DInSAR), as is the case for off shore areas. New mission concepts, such as those proposed for the Mass change And Geosciences International Constellation (MAGIC), have been recently assessed as capable of providing significant enhancements in the spatial and temporal resolution of gravity field products, resulting in turn in unprecedented impact on the scientific applications, including earthquake gravimetry [1]. The evolution of sensors beyond classic electrostatic accelerometers, such as future applications of Cold Atom Interferometry (CAI) on space borne platforms, has the potential to allow further steps forward in sensing the mass transport in the Earth’s system.In this context, we aim at assessing the impact of Quantum Space Gravimetry (QSG) to earthquake detectability, by modelling a database of synthetic earthquake gravity signal, including the effect of post-seismic viscoelastic relaxation, and setting up a strategy do assess their detectability in simulated time-varying gravity field products. We compute the gravity change in time using the QSSPSTATIC [2] code and a workflow we developed to obtain the spherical harmonics (SH) expansion of the geopotential change through time. We designed the structure of this synthetic earthquake data to be easily included as part of time-varying signals used in simulations, improving the solid-Earth component of models such as AOHIS [3]. In this contribution we present the detection threshold of different events, real earthquakes ranging from Mw 9.2 to 7.6 with an assortment of depths, locations and focal mechanisms, using an SNR assessment in the spectral domain, between the modelled signal and retrieval errors (residuals) obtained from mission simulations.This work is supported by the ESA QSG4EMT study, a collaboration between Technical University of Munich, Politecnico di Milano, Delft University of Technology, HafenCity University Hamburg, University of Bonn and University of Trieste.[1] Daras I., March G., Pail R., Hughes C. W., Braitenberg C., Güntner A., Eicker A., Wouters B., Heller-Kaikov B., Pivetta T., & Pastorutti, A. (2023). Mass-change And Geosciences International Constellation (MAGIC) expected impact on science and applications. Geophysical Journal International, 1288–1308. https://doi.org/10.1093/gji/ggad472[2] Wang, R., Heimann, S., Zhang, Y., Wang, H., & Dahm, T. (2017). Complete synthetic seismograms based on a spherical self-gravitating Earth model with an atmosphere-ocean-mantle-core structure. Geophysical Journal International, 210(3), 1739–1764. https://doi.org/10.1093/gji/ggx259[3] Dobslaw, H., Bergmann-Wolf, I., Dill, R., Forootan, E., Klemann, V., Kusche, J., & Sasgen, I. (2015). The updated ESA Earth System Model for future gravity mission simulation studies. Journal of Geodesy, 89(5), 505–513. https://doi.org/10.1007/s00190-014-0787-8