Gravity Changes Research Articles

Changes in gravity affect neuromuscular control, biomechanics and muscle-tendon mechanics in energy storage and dissipation tasks.

This study evaluates neuromechanical control and muscle-tendon interaction during energy storage and dissipation tasks in hypergravity. During parabolic flights, while 17 subjects performed drop jumps (DJs) and drop landings (DLs), electromyography (EMG) of the lower limb muscles was combined with in vivo fascicle dynamics of the gastrocnemius medialis, 2D kinematics, and kinetics to measure and analyze changes in energy management. Comparisons were made between movement modalities executed in hypergravity (1.8G) and gravity on ground (1G). In 1.8G, ankle dorsiflexion, knee joint flexion, and vertical center of mass (COM) displacement are lower in DJs than in DLs; within each movement modality, joint flexion amplitudes and COM displacement demonstrate higher values in 1.8G than in 1G. Concomitantly, negative peak ankle joint power, vertical ground reaction forces, and leg stiffness are similar between both movement modalities (1.8G). In DJs, EMG activity in 1.8G is lower during the COM deceleration phase than in 1G, thus impairing quasi-isometric fascicle behavior. In DLs, EMG activity before and during the COM deceleration phase is higher and fascicles are stretched less in 1.8G than in 1G. Compared to the situation in 1G, highly task-specific neuromuscular activity is diminished in 1.8G, resulting in fascicle lengthening in both movement modalities. Specifically, in DJs, a high magnitude of neuromuscular activity is impaired, resulting in altered energy storage. In contrast, in DLs, linear stiffening of the system due to higher neuromuscular activity combined with lower fascicle stretch enhances the buffering function of the tendon, and thus the capacity to safely dissipate energy.

Rapid and Simple Method for Measuring Petroleum Asphaltenes by the Centrifugation Technique.

Asphaltenes are heavy constituents of crude oil which affect the flow and viscosity of crude oil. They also stabilize water-in-oil emulsions which makes the separation process of water from oil during the primary treatment processes for crude oils more difficult and costly. Measuring asphaltenes has great importance, especially for crude oil production companies. Gravimetric and spectroscopic measurement methods are the basic techniques used by international references such as ASTM and IP. A new methodology has been introduced as a modification of ASTM D6560 gravimetric methodology by using the centrifugation technique in the separation of asphaltenes for different oil samples with the API gravity change from 17.4 (oil S1) to 39.8 (oil S5). The new methodology has the advantages of consuming little time, and multiple sample processing and can be done in the field and also in the lab. Moreover, it has good repeatability, reproducibility, and working range values compared to the reference gravimetric ASTM and IP methods. The repeatability of the new method was found to be 8.0% at its maximum value (S1, has a low asphaltene content), while the minimum value was found to be 3.75% (S10, has the highest asphaltene content). It was found that the maximum reproducibility value was 17.0% for the S1 sample and the minimum was 0.0% for S9 and S10 samples.

Delineating a volcanic aquifer using groundwater-induced gravity changes in the Tatun Volcano Group, Taiwan

The Tatun Volcanic Group (TVG) is an active volcanic system that poses potential volcanic hazards to northern Taiwan. Groundwater migration can be sensitive to volcanic activities and can induce temporal gravity changes. Here we conducted four gravity measurement campaigns in 2012 with two CG5 relative gravimeters at a total of 31 gravity monitoring sites to probe the spatiotemporal groundwater variability in the TVG area. With careful adjustments to the gravity measurements, the standard point gravity error was approximately 8 μGal on average. The observed gravity changes were compared with the groundwater-induced gravity variations derived from two hydrological models: the continuous flow model that consisted of one permeable layer (Model A) and a dynamic groundwater flow model that used the hydrological solver MODFLOW (Model B). The results show that only gravity observations in the central TVG match the simulated gravity pattern, i.e., the hydrology in the central TVG follows free groundwater flows within the interconnected and porous strata. On the other hand, inconsistencies between simulated and observed gravity changes range from + 40 to – 80 μGal. The discrepancies were located at the eastern and western areas in the TVG and showed opposite variations over time. This pattern of temporal variability cannot be attributed to the use of shallow aquifer models that merely reflect the surface recharges and discharges. We infer that the pattern stems from deep flows, such as hydrothermal fluids alternately replenishing aquifers to the east and west of the TVG, i.e., deep fluid conduits may have developed to the east and west of the TVG and bypassed the central area.

Multiphysics Modeling of Volcanic Unrest at Mt. Ruapehu (New Zealand)

AbstractPre‐eruptive signals at the crater lake‐bearing Mt. Ruapehu (New Zealand) are either absent or hard to identify. Here, we report on geophysical anomalies arising from hydrothermal unrest (HTU) and magmatic unrest (MU) using multiphysics numerical modeling. Distinct spatio‐temporal anomalies are revealed when jointly solving for ground displacements and changes in gravitational and electrical potential fields for a set of subsurface disturbances including magma recharge and anomalous hydrothermal flow. Protracted hydrothermal injections induce measurable surface displacements (>0.5 cm) at Ruapehu's summit plateau, while magmatic pressurization (5–20 MPa) results in ground displacements below detection limits. Source density changes of 10 kg/m3 (MU simulations) and CO2 fluxes between 2,150 and 3,600 t/d (HTU simulations) induce resolvable residual gravity changes between +8 and −8 μGal at the plateau. Absolute self‐potential (SP) anomalies are predicted to vary between 0.3 and 2.5 mV for all unrest simulations and exceed the detection limit of conventional electric surveying. Parameter space exploration indicates that variations of up to 400% in the Biot‐Willis coefficient produce negligible differences in surface displacement in MU simulations, but strongly impact surface displacement in HTU simulations. Our interpretation of the findings is that monitoring of changes in SP and gravity should permit insights into MU at Ruapehu, while HTU is best characterized using ground displacements, residual gravity changes and SP anomalies. Our findings are useful to inform multiparameter monitoring strategies at Ruapehu and other volcanoes hosting crater lakes.

Investigation of temperature sensitivity of a MEMS gravimeter based on geometric anti-spring.

This paper describes a technique for temperature sensitivity or thermal sag measurements of a geometric anti-spring based microelectromechanical system (MEMS) gravimeter (Wee-g). The Wee-g MEMS gravimeter is currently fabricated on a (100) silicon wafer using standard micro-nano fabrication techniques. The thermal behavior of silicon indicates that the Young's modulus of silicon decreases with increase in temperature (∼64 ppm/K). This leads to a softening of the silicon material, resulting in the proof mass displacing (or sagging) under the influence of increasing temperature. It results in a change in the measured gravity, which is expressed as temperature sensitivity in terms of change in gravity per degree temperature. The temperature sensitivity for the silicon based MEMS gravimeter is found to be 60.14-64.87, 61.76, and 62.76 µGal/mK for experimental, finite element analysis (FEA) simulation, and analytical calculations, respectively. It suggests that the gravimeter's temperature sensitivity is dependent on the material properties used to fabricate the MEMS devices. In this paper, the experimental measurements of thermal sag are presented along with analytical calculations and simulations of the effect using FEA. The bespoke optical measurement system to quantify the thermal sag is also described. The results presented are an essential step toward the development of temperature insensitive MEMS gravimeters.

Computational study of temperature and density perturbations on atmospheric dynamics

This study examines the perturbation effect of temperature and density of moist air on atmospheric variables at 9°1’48″N, 38°44’24″E and 6.324 km above the Earth’s surface. The atmosphere is a compressible neutral moist air flowing on a rotating Earth as a model and it’s basic atmospheric parameters such as gas constant, transport coefficients, mixing ratio and specific heat capacities are considered to be temperature dependent and the Earth’s gravity changes with latitude and altitude. To describe the dynamics, we carried out a numerical computation using finite difference method on an unstaggered grid. Our results revealed that the response of all the variables have a plane wave pattern, in which specific heat capacities (SHCs), resultant wind speed (RWS) and water vapor mixing ratio (MR) increase with time at each latitude but vertical wind speed (VWS), specific enthalpy (SE) and pressure decrease with time at each latitude. The increase of MR with time is the result of water vapor flux into the air parcel and the decrease of SE and increase of RWS with time is the result of thermal energy to mechanical energy transformation. The decrease of VWS with time is the effect of the viscous force due to temperature dependence of viscosity.

Forward Modelling on Gravity Anomalies Fault Model Using MATLAB Mathworks

The gravity method is one of the geophysical methods utilized to determine the subsurface conditions of the earth according to differences in rock mass density below the surface. In the exploration of gravity requires an initial description as a reference for measurement. The synthetic modelling carried out this time is a forward modelling of fault anomalies carried out with the help of Grav2dc and Matlab Mathworks software. This study aims to compare the results of synthetic modelling using Grav2dc software and Matlab Mathworks as well as to test whether the program built can run well or not. The model parameters utilized are the density value of 1 kg/m3 with a deep plate depth of 50 m, a shallow plate depth of 150 m and the location of the fault at a depth of 150 m with a thickness of 40 m. The data processing in this study used two pieces of software, are Grav2dc and Matlab MathWorks to compare and test whether the processing results using Matlab MathWorks software were in accordance with the synthetic model processed using Grav2dc software. The results obtained from this study are the fault model obtained from processing using Matlab MathWorks and Grav2dc software with model parameters in the form of density and depth, where density and depth have a role in shaping the value of the change in gravity.

Single Cell in a Gravity Field.

The exploration of deep space or other bodies of the solar system, associated with a long stay in microgravity or altered gravity, requires the development of fundamentally new methods of protecting the human body. Most of the negative changes in micro- or hypergravity occur at the cellular level; however, the mechanism of reception of the altered gravity and transduction of this signal, leading to the formation of an adaptive pattern of the cell, is still poorly understood. At the same time, most of the negative changes that occur in early embryos when the force of gravity changes almost disappear by the time the new organism is born. This review is devoted to the responses of early embryos and stem cells, as well as terminally differentiated germ cells, to changes in gravity. An attempt was made to generalize the data presented in the literature and propose a possible unified mechanism for the reception by a single cell of an increase and decrease in gravity based on various deformations of the cortical cytoskeleton.

Changes towards stable good somatic condition and increased gonad investment of Norwegian spring-spawning herring (Clupea harengus) after 2005 are linked to extended feeding period

Norwegian spring spawning herring (Clupea harengus) migrate from spawning areas on the Norwegian shelf in February-March to feeding areas in the Norwegian Sea in April-August, returning to wintering areas in northern Norwegian waters from September onwards when feeding ceases. After around 2005 the Norwegian Sea has become warmer and here we address recent changes in migration, somatic condition and gonad development of herring related to these changes. Analyses were based on combined Norwegian, Icelandic and Faroese data on fishery (~81% of total commercial catch) and biological parameters from an extensive material of individual fish (n = 310749) during the period 1994-2019. Fishery data demonstrated large-scale changes in herring distribution over the study period. This was further supported by spatiotemporal modelling of body growth, somatic condition, gonad development and concurrent centre of gravity changes of the sampled fish. After 2005 the population showed a clear tendency of being distributed farther south-westwards in the Norwegian Sea during feeding and returning to wintering areas later in the year. This tendency increased with age, and with body length and somatic condition within age groups. Moreover, the somatic condition increased for all age groups from the early 2000s towards stable high levels after 2005, mainly due to extra weight gained from extended feeding into the autumn. Length at age decreased continuously during 2003-2010 for all age groups, suggesting impact of density dependent limiting factors but also that the environmental shift may have led to immediate poorer feeding conditions early in the year. Hence, extra energy from extended autumn feeding was rather invested into gonad weights tending to increase over the study period. Mechanisms behind the observed changes are likely linked to spatial and seasonal changes in zooplankton abundance. Overall, zooplankton production possibilities along the frontal areas in the south-western part of the Norwegian Sea have likely increased after the general environmental shift. This also includes a change towards increased probabilities of an additional second generation of some copepods developing in warmer waters, facilitating a prolonged feeding period for herring.

How Complex Groundwater Flow Systems Respond to Climate Change Induced Recharge Reduction?

Our recent knowledge about the role of different fluid driving forces in the response of groundwater flow systems to climate change is still limited. This current study aimed to evaluate possible spatial and temporal changes in complex, gravity- and overpressure-driven groundwater flow systems induced by climate change and look for general trends and characteristics of the flow field using 2D transient groundwater flow simulations. Results showed significant large-scale changes in the transient subsurface flow field and flow dynamics due to recharge reduction. Local gravity-driven flow systems are the most vulnerable to atmospheric processes, while overpressured regimes are expected to be independent of direct climatic variability. By the involvement of different degrees of overpressure, it was revealed that, as the degree of overpressure increases, the penetration depth of the topography-driven local flow systems decreases. The higher the overpressure, the lower the climate change-induced groundwater level decrease over time, suggesting the buffering effect of overpressure as a fluid driving force in the flow systems’ response to the changes in hydrologic parameters. The main novelty of the study is the involvement of different fluid driving forces in the evaluation with the combination of a regional scale investigation, which is unique in the context of climate change effects on groundwater systems.

Pre-eruptive excess volatiles and their relationship to effusive and explosive eruption styles in semi-plugged volcanoes

Understanding the role of various factors influencing eruption style is challenging, but it can aid in adapting different hazard mitigations and crisis responses for explosive or effusive events. Here, we focus on the role of magma storage conditions in controlling eruption styles at basaltic andesite volcanoes, and how they can be related to monitoring data. We study the cycle of explosive (1990, sub-Plinian) → effusive (2007, dome) → explosive (2014, sub-Plinian) eruptions from Kelud (Kelut) volcano, Indonesia. We conducted petrological analyses of the eruption products and phase equilibria experiments using pumice and explored a range of temperatures, pressures, oxygen fugacity, and volatile contents. We show that we can reproduce the main mineral assemblage (plagioclase ± pyroxenes ± magnetite ± amphibole ± olivine) and phenocryst content (30–50 wt%) of the magmas from the three eruptions at T = 975 ± 39°C, p = 175 ± 25 MPa, fO2 = nickel–nickel oxide buffer, and about 4–6 wt% water in the melt (ca. 3 to 5 wt% and ca. 4 to 7 wt% for the 1990 and 2014 eruptions, respectively). However, geothermobarometric results also indicate that some crystals of amphibole were sourced from higher pressures. We infer from a synthesis of our data and historical observations that the high phenocryst content of the 2007 dome (∼70 wt%) likely resulted from slow magma ascent toward the surface alongside progressive degassing and re-equilibration at a lower volatile content (∼1 wt% water in the melt). Mass balance calculations on the sulfur budget of the 1990, 2007, and 2014 magmas show that the explosive events contained an excess fluid phase at pre-eruptive conditions, and we propose that this led to their higher explosivity compared to the 2007 dome. The accumulation of excess fluids during decadal-long repose depends on how plugged the volcanic system is, or its ability to passively release magmatic fluids, prior to eruption. Such condition could be inferred from monitoring records, including changes in gravity of the plumbing system over time, and thus contribute to better anticipate eruptive style.

The Biomechanical Analysis of Jumping Difficulty Movement in National Traditional Sports

In order to explore the relevant factors and the completion of difficult movements, this paper is an important theoretical basis for improving and constructing the evaluation of athletes’ movement quality. It presents a kinematic analysis of the difficult movements of competitive Tai Chi, taking the difficult movements of the swirl group of competitive aerobics as the research object. The data is collected by different methods. When completing difficult movements, due to different personal exercise habits, this paper takes the right leg as the swinging leg and the left leg as the take-off leg when completing the difficult movements. The test object in this paper adopts the traditional three-step up-step method. The starting time of the take-off stage is consistent with the illustration. By consulting experts for the stage division of the difficult movement, the two movement stages are equally divided into three stages according to the needs of the research: take-off, soaring, and landing. The results show that, from the moment the left foot hits the ground to the moment of maximum cushioning, the angles of the right knee are 176.48° and 165.06°, respectively, and the flexion of the right knee is not large; especially when the left foot touches the ground, the right leg is close to a straight line, indicating that the athlete’s body is in a straight line. The posture is relatively good, the left foot is used as the grounding leg, the angle of the knee joint is reduced from 160.82° to 124.41°, and the left knee buffer angle is 36.40°. As the right leg swings to the ground, the left knee and left hip are slightly stretched, and the right knee and right hip are slightly flexed. This change is also reflected in the fact that the center of gravity changes from the direction of the horizontal speed at this stage. Move the left side of the body slightly to the right. Difficulty movements are different in the landing stage, and their joint parameters are also different. When the landing leg touches the ground, there is no significant difference in the maximum cushioning time, the degree of torsion of the shoulder and the hip is different, the relative rotation position of the shoulder and the hip is opposite, and the posture of the shoulders at the time of landing is different. In teaching, the landing leg and the end direction of the rotation are not the same; it is necessary to strengthen the strength training of the legs, to experience the force feeling of the different degrees of rotation of the shoulder joint and the hip joint, as well as the spatial perception ability, and take the initiative to actively land. The magnitude of the rear cushion and the coordination of the trunk and the limbs are used to avoid unnecessary damage during the landing phase.

Surface deformations and gravity changes caused by pressurized finite ellipsoidal cavities

SUMMARY We develop quasi-analytical solutions for the surface deformation field and gravity changes due to the pressurization of a finite (triaxial) ellipsoidal cavity in a half-space. The solution is in the form of a non-uniform distribution of triaxial point sources within the cavity. The point sources have the same aspect ratio, determined by the cavity shape, while their strengths and spacing are determined in an adaptive manner, such that the net point-source potency per unit volume is uniform. We validate and compare our solution with analytical and numerical solutions. We provide computationally efficient MATLAB codes tailored for source inversions. This solution opens the possibility of exploring the geometry of shallow magma chambers for potential deviations from axial symmetry.

Months of Gravity Changes Preceded the Tōhoku Earthquake

Using GRACE satellite data, researchers discovered anomalous gravimetric signals that occurred before a seismic event that started deep within Earth.

Changes of Physical and Chemical Properties for Making Raw Materials and Reproductions According to Manufacturing Stages in Traditional Korean White Porcelain

We made a Korean white porcelain or Joseon Baekja jar and based on the raw materials used and reproductions of each stage, we aimed to compare and analyze the physicochemical changes of the raw materials such as clay at each manufacturing stage, as well as identify the characteristics and correlations. Although the basic main components of clay and glaze material are similar, their texture becomes denser in the process of bisque firing pottery (Chobeol-pyeon) and glaze firing pottery (Jaebeol-pyeon), and we confirmed that in addition to the tendency of increasing vitrification, low-temperature minerals such as mica and illite gradually disappeared, while high-temperature minerals such as cristobalite were newly created. This phenomenon has also been verified by the rapid decrease in absorption rate while the change in specific gravity was small. In addition, the color was greatly affected by the firing atmosphere, and the yellow-red chromaticity of the raw materials was higher during bisque firing but showed a rapidly decreasing characteristic during glaze firing. The value of magnetic susceptibility, which is related to iron (Fe) component, showed a tendency to decrease in glaze firing pottery. CT images were confirmed as a method that can indirectly estimate the change in the material properties of the object step-by-step for the entire object. In conclusion, the study of manufacturing stages of reproduction can provide basic data for scientific research on the estimation of porcelain and pottery making technology and changes in raw materials.

Reducing Virus Infection Risk in Space Environments through Nutrient Supplementation.

Space exploration has brought many challenges to human physiology. In order to evaluate and reduce possible pathological reactions triggered by space environments, we conducted bioinformatics analyses on the methylation data of the Mars 520 mission and human transcriptome data in the experiment simulating gravity changes. The results suggest that gene expression levels and DNA methylation levels were changed under the conditions of isolation and gravity changes, and multiple viral infection-related pathways were found in the enrichment analysis results of changed genes including Epstein Barr virus (EBV) infection, Hepatitis B virus (HBV) infection, Herpes simplex virus (HSV) infection and Kaposi’s sarcoma-associated herpesvirus (KHSV) infection. In this study, we found that Epigallocatechin-3-gallate (EGCG) and vitamin D are helpful in reducing viral infection risk. In addition, the causal associations between nutrients and viral infections were calculated using Two sample Mendelian Randomization (2SMR) method, the results indicated that vitamin D can reduce EBV infection and HBV infection risk. In summary, our study suggests that space environments increase the risk of human viral infection, which may be reduced by supplementing EGCG and vitamin D. These results can be used to formulate medical plans for astronauts, which have practical application value for future space exploration.

Transcrustal Compressible Fluid Flow Explains the Altiplano‐Puna Gravity and Deformation Anomalies

AbstractEnigmatic large‐scale (>150 km wide) ground deformation in southern Bolivia has been ongoing for more than 50 year. Concurrent changes in gravity recorded between 2010 and 2018 imply minor changes in subsurface density in the absence of significant mass changes. Numerical modeling of the gravity changes and concurrent InSAR LOS displacements gives annual bulk density changes of 0.002 kg m−3 in the Altiplano‐Puna Magma Body (APMB) and −0.03 kg m−3 in a vertical bulge‐column ensemble beneath Uturuncu volcano. We propose that the transcrustal migration of fluids from the APMB to shallower crustal levels by compressible flow is the source of ground deformation. Localized ground subsidence south of Uturuncu can be best explained by a density decrease of 20 ± 5 kg m−3 between 2011 and 2013 in a hydrothermal reservoir. Our findings contribute to the growing recognition of transcrustal fluid migration as a source of volcanic unrest.

Plausible Detection of Feasible Cave Networks Beneath Impact Melt Pits on the Moon Using the Grail Mission

In the future, when humans build their bases on terrestrial planets and their moons, caves will be the safest place for inhabitation. Large holes, believed to be cave entrances, have been discovered on the Moon, along with small features called “impact melt pits.” In the Gravity Recovery and Interior Laboratory (GRAIL) gravity model, which is expressed in spherical harmonics (SH), it is difficult to express the gravity anomaly created by a small empty space below the surface. Nevertheless, we propose that a cave network, akin to an anthill, exists under the impact melt pits discovered on the Moon. This is because we think it is natural to apply a network created by Earth’s small caves to the Moon. We obtained accurate Bouguer gravity measurements by calculating regional crustal density using localized admittance of the study area and detected weak gravity (mass deficit) information. By increasing the degrees and order of SH at regular intervals, we estimated the change in gravity at a specific position at high degrees and order, thereby extracting shallow depth information. To validate our method, we compared our results with those of existing studies that analyzed the previously known Marius Hills Hole (MHH) area. The analysis of seven regions in our study area revealed a mass deficit in some impact melt pits in four lunar regions (Copernicus, King, Stevinus, and Tycho). We propose that there is a cave network in this region, indicated by the gravitation reduction in the impact melt pits region. Our results can be useful for the selection of landing sites for future in situ explorations of lunar caves.

Sub Surface Structure Modelling Area around Sub district Gantiwarno, District Klatenusing by Gravity Method

The earthquake that happened on 27th May 2006 in Yogyakarta and its surrounding caused terrible damageas well as thousands of dead victims. Such an earthquake was caused by horizontal Opak’s Fault activationand it triggered the emergence of Dengkeng’s Fault movement located at the eastern part of the northernOpak’s Fault. To mitigate the disaster that might occur in the future, the channel and the condition underDengkeng’s Fault need to be mapped. One of the methods that could be used to recognize the under surfacecondition is the gravity method which is based on the measurement of gravity field variation on the earth’ssurface. The existence of a fault would change the condition of rocks in such fault channel zone so that itinfluences the local gravity change. Therefore, on this opportunity, research of Dengkeng’s Fault is carriedout using the gravity method. The measurement of the gravity field has been done in 94 points using LacosteRomberg Gravitymeter type G-1118 MVR. The height of the measurement point was measured usingGPS Altus APS-3 differential, and the research coordinate was measured using GPS Garmin III Plus. Dataon the gravity field that had been obtained was corrected so that complete anomaly Bouguer (ABL) isobtained. Further, the regional component of the ABL value is separated from its local component using anupward continuation method. The target that would be identified is shallow so that the local anomaly thatwould be analyzed uses the second vertical derivative (SVD) and modeled in 3 dimensions using OasisMontaj software. Second vertical derivative type of fault. 3-dimensional modeling was used to identify theunder surface structure of the research area comprehensively. The result of the analysis using the secondvertical derivative shows that Dengkeng’s Fault is a strike-slip fault with the west-east direction. To clarifythe under the surface condition from the 3-dimensional modeling, incisions were made to the Z-axis direction(vertically) and X-axis direction. Z-axis direction modeling shows that the fault in the research area starts tobe seen at the depth of 500 meters to 3500 meters to the west-east. X-axis direction modeling shows that thefault was located at Easting 444500 meter and Northing 9141000 meters to the Easting 456250 and Northing9139000. Based on the modeling result, it could be seen that the southern part block of Dengkeng’s movedto the east, while the northern part block moved to the west.

A First Reliable Gravity Tidal Model for Lake Nasser Region (Egypt)

In the framework of the French–Egyptian Imhotep Project, two spring gravimeters have been installed in the area of Lake Nasser (Egypt) with the aim to establish a first reliable gravity tide model for the region. The two tidal gravity stations are located in Aswan, on the northern edge of the lake and in Abu Simbel in the south, respectively. This study was mainly aimed to obtain a reliable model of the crustal response to tidal forces and, consequently, to increase the accuracy of the geodetic observations, to be used in future geophysical studies in this region as well as to investigate the effect of the Lake level variations on the crustal deformation and related gravity changes. Nearly 3 years of gravity records (from May 2018 to April 2021) were collected. Since no scale factor was available for the two gravimeters, the first step of this study was to achieve a reliable calibration for each of the two collected gravity signals. After removing the instrumental drift, spikes, steps and tares, both gravimeters have been calibrated by fitting the output signal against a synthetic reference signal based on the body tidal gravity response due to Wahr-Dehant Earth model and FES2014 ocean tidal loading model. The calibrated signals have been analyzed with ET34-X-V80 software for tidal analyses. This enabled us to retrieve a set of frequency-dependent gravity factors (amplitude and phase) for the main tidal waves, as well as to obtain gravity residuals. It turns out that the accuracy of the amplitude estimates for the main tidal waves is 0.2 ÷ 1% for LCR_ET16 in Aswan and 1 ÷ 10% for the LCR_D-218 in Abu Simbel. To improve the tidal model at Abu Simbel, LCR_ET16 was stopped in Aswan and relocated there. The first 90 days of gravity recordings from ET16 at Abu Simbel provide promising results, with an accuracy of the order of 0.1% for the main tidal waves, even better than the results obtained in Aswan. The residual gravity signal after tidal subtraction at Aswan is in the range of ± 50 µGal. Further analyses of the instrumental contribution are however needed before to be able to interpret this gravity signal in terms of surface loading (i.e. changes in the water level of Lake Nasser) or underground hydrology.