To dampen periodic off-levelling motions within an inertial platform while undergoing horizontal accelerations of the same period and to achieve a levelling accuracy of a few tens of arcseconds with that system,an int...To dampen periodic off-levelling motions within an inertial platform while undergoing horizontal accelerations of the same period and to achieve a levelling accuracy of a few tens of arcseconds with that system,an internally damped inertial platform for a marine scalar gravity system was the developed.Methods for attenuating horizontal acceleration and reducing off-levelling error by a satisfactory gyro-levelling loop,which are fundamental to the internally damped inertial platform,were designed and implemented.In addition,phase delays are introduced by the levelling loop.The resulting off-levelling gravity errors were analyzed and modeled.A series of tests on a motion simulator were performed in laboratory for a variety of simulated sea conditions.We found that the motion of the platform is a function of the amplitude and period of the simulated ship motions and ranges between 10 and 40 arcseconds.In addition,the phase lag between platform motion and ship motion is not constant but ranges 180°-270°,depending on the period and amplitude of the motion.Then,the platform,on which a gravimeter was mounted,was installed on the R/V Shiyan 2 to conduct a gravity survey in the South China Sea.Despite rough sea conditions,it was shown that in short periods of 2-30 s,the off-levelling angle was less than 30 arcseconds,and the phase lagged the horizontal acceleration by 230°-260°.From a repeated survey line and intersecting survey points,the estimated errors of gravity measurements were between 1.3 and 1.7 mGal.The marine measurements results were compared with those of satellite altimetry data and show a mean value of 0.5 mGal in a standard deviation of 1.5 mGal.展开更多
The satellite gravimetry technology effectively recovers the global Earth’s gravity field.Since 2000s,HL-SST satellite CHAMP,LL-SST satellite GRACE,Gravity Gradient Measurement(GGM)satellite GOCE have been launched s...The satellite gravimetry technology effectively recovers the global Earth’s gravity field.Since 2000s,HL-SST satellite CHAMP,LL-SST satellite GRACE,Gravity Gradient Measurement(GGM)satellite GOCE have been launched successfully,producing some Earth’s gravity models solely from satellites data.However,the space and time resolution of the Earth’s gravity fields do not adequately satisfy scientific objectives.The main reason is that the gravimetry satellites are not enough and observation data insufficient.The paper outlines the current and future status of Chinese gravity satellite missions.The Chinese gravimetry satellite system,named Chinese Gravimetry augment and Mass change exploring mission(ChiGaM),successfully launched in Dec.2021 after four years of production and over a year of calibration and valiation.The accelerometer,K-band ranging system and the three stellar sensors,among others,were precisely calibrated and trimmed.The satellite mass center was determined and coordinated with the proof center of accelerometer with an accuracy 100μm.The inter-satellite ranging system and BDS/GPS receiver operate together seamlessly.The range and range rate noise is less than 3μm/Hz^(1/2) and 1μm/s/Hz^(1/2),respectively,in band of 0.025~0.1 Hz.The electrostatic suspension accelerometer is working well.Its high-sensitive axis noise level is 3×10^(-10) m/s^(2)/Hz^(1/2)near the frequency 0.1 Hz,and 1×10^(-9) m/s^(2)/Hz^(1/2) for the less-sensitive axis.Meanwhile the BDS/GPS receiver is used to achieve data for precise orbit determination,yielding an orbit result with accuracy better than 2 cm.When compared with KBR observations,the RMS of the bias is less than 1 mm.Besides above mission,next gravimetric satellite is being developed now.TQ-2 mission is designed as a totally experimental satellite for gravitational wave detection at low Earth orbit,which can detect the Earth’s gravity field simultaneously.The Bender-type mission is considered the most promising configuration for TQ-2 and consists of two polar satellites and two inclined satellites.Due to the extra observations at the east-west direction derived from the inclined satellite pair,significant improvements has been made in detecting temporal signals with higher accuracy and spatial-temporal resolution.To achieve the scientific goal,the ACC MBW can shift from 0.001~0.1 Hz to 0.004~0.1 Hz for ACC,and the LRI MBW can shift from 0.01~1 Hz to 0.1~1 Hz.For future research,a gravimetric potential survey using cold-atomic-clock based on the general relativity theory,cold atom gradiometer should be pursued.Gravimetric technologies should be mined and researched,and the gravimetry satellite constellation should be developed,so as to improve the time resolution and space resolution for meeting the requirements of geophysics,geodesy,earthquake,water resources environment,oceanography,etc.展开更多
Gravity field is the most basic physical field generated by the material properties of the Earth system.It reflects the spatial distribution,movement and change of materials determined by the interaction and dynamic p...Gravity field is the most basic physical field generated by the material properties of the Earth system.It reflects the spatial distribution,movement and change of materials determined by the interaction and dynamic process inside the Earth.Over the years,a variety of technical means have been used to detect the Earth’s gravity field and supported numerous studies on the global change,resource detection,geological structure movement,water resources change and other related fields of research.Here is part of the progress in surface and marine gravimetry obtained by Chinese geodesy scientists from 2019 to 2023 from the following aspects,including:①Continuous gravity network in Chinese mainland;②Application of superconducting gravity measurement;③Network adjustment for continental-scale gravity survey campaign and data quality control;④Regional time-variable gravity field and its application;⑤Research progress on novel technologies for gravity inversion;⑥Research progress on marine gravity field determination;⑦Application research on marine gravity field.展开更多
Natural gas (NG) is one of the most important sources of energy for industrial and domestic consumption in the present era because it is cheap and free from sulfur impurities. Therefore, accurate and precise measureme...Natural gas (NG) is one of the most important sources of energy for industrial and domestic consumption in the present era because it is cheap and free from sulfur impurities. Therefore, accurate and precise measurement of its composition is of fundamental importance for trade reasons. To improve the quality of NG gas measurements, certified reference materials (CRMs) should be used for calibration of measuring equipment in order to ensure the traceability of the measurement results to the SI units. For the traceability purpose, a multicomponent natural gas mixture was prepared gravimetrically as a reference material according to ISO 6142 from pure helium, hydrogen, n-pentane, i-pentane, n-butane, i-butane, propane, ethane, hexane, methane and nitrogen. The preparation was done in two dilution steps in 5 L aluminum cylinders. The calculated mole fractions and associated uncertainties of natural gas components were verified by a dual GC-FID/TCD system in accordance with ISO 6143 calibrated by a series of primary gas mixtures (CRMs) produced by an NMI. The results obtained by gravimetry and by GC measurements have been checked for compatibility as required by ISO 6142 and were found in very good agreement. Details of the preparation and calculation of the mole fractions and uncertainties of all gas components are explained in this article.展开更多
Variation of terrestrial water storage in the Hebei plain area from March 2010 to June 2014 was studied using ground gravimetry combined with vertical displacement data from the Global Navigation Satellite System.Resu...Variation of terrestrial water storage in the Hebei plain area from March 2010 to June 2014 was studied using ground gravimetry combined with vertical displacement data from the Global Navigation Satellite System.Results show that observed gravity variation in this area increased continuously,basically reflecting a trend toward land subsidence.With the effect of this subsidence removed,a dominantnegative change in gravity variation was evident,reflecting an average rate of decrease in terrestrial water in this area of 0.10±0.053 m/y,and this is equivalent to a volume of 81.5±43.2×108 m^(3)and is consistent with the spatial distribution of groundwater change from measured hydrologic data.These results can be an essential reference and supplement for the study of terrestrial water variation in the Hebei plain area,and indicate that ground surface gravimetry can be used as an important mean for studying changes in terrestrial water.展开更多
Gravimetry technical guides are the scientific basis for air-sea gravimetry. However, the existing technical guides in China are behind the application requirements. This study analyzed the most important indicators o...Gravimetry technical guides are the scientific basis for air-sea gravimetry. However, the existing technical guides in China are behind the application requirements. This study analyzed the most important indicators of air-sea gravimetry, including the density of survey lines, gravimetry accuracy and space resolution, stability and reliability of the air-sea gravimeter, and proposed a gravimetry accuracy assessment system consisting of gravity RMS of error, systematic error and mean error, and an assessment system for the gravimeter stability consisting of the relative accuracy of the scale value, monthly zero-drift, RMS of the monthly nonlinear zero-drift variation and the threshold of the monthly nonlinear zero-drift variation. The mathematic models for the measurement point determination in shipborne gravimetry, E tv s correction for airborne gravimetry, platform tilt correction and evaluation air-sea gravimetry were also analyzed and modified. This work will provide technology support for the composition of the military-civil air-sea gravimetry technical guides.展开更多
We propose a fast local level set method for the inverse problem of gravimetry.The theoretical foundation for our approach is based on the following uniqueness result:if an open set D is star-shaped or x3-convex with ...We propose a fast local level set method for the inverse problem of gravimetry.The theoretical foundation for our approach is based on the following uniqueness result:if an open set D is star-shaped or x3-convex with respect to its center of gravity,then its exterior potential uniquely determines the open set D.To achieve this purpose constructively,the first challenge is how to parametrize this open set D as its boundary may have a variety of possible shapes.To describe those different shapes we propose to use a level-set function to parametrize the unknown boundary of this open set.The second challenge is how to deal with the issue of partial data as gravimetric measurements are only made on a part of a given reference domainΩ.To overcome this difficulty,we propose a linear numerical continuation approach based on the single layer representation to find potentials on the boundary of some artificial domain containing the unknown set D.The third challenge is how to speed up the level set inversion process.Based on some features of the underlying inverse gravimetry problem such as the potential density being constant inside the unknown domain,we propose a novel numerical approach which is able to take advantage of these features so that the computational speed is accelerated by an order of magnitude.We carry out numerical experiments for both two-and three-dimensional cases to demonstrate the effectiveness of the new algorithm.展开更多
A growing interest in small body exploration has motivated research into the rapid char-acterization of near-Earth objects to meet economic or scientific objectives.Specifically,knowledge of the internal density struc...A growing interest in small body exploration has motivated research into the rapid char-acterization of near-Earth objects to meet economic or scientific objectives.Specifically,knowledge of the internal density structure can aid with target selection and enables an understanding of prehistoric planetary formation to be developed.To this end,multi-layer extensions to the polyhedral gravity model are suggested,and an inversion technique is implemented to present their effectiveness.On-orbit gravity gradiometry is simulated and employed in stochastic and deterministic algorithms,with results that imply robustness in both cases.展开更多
Studies have been conducted on the corrosive behavior of magnesium in aqueous sulfate electrolytes(0.5 mol/L MgSO_(4);0.5 mol/L Na2SO_(4);0.5 mol/L MgSO_(4)+0.5 mol/L Na2SO_(4)).The composition structure and morpholog...Studies have been conducted on the corrosive behavior of magnesium in aqueous sulfate electrolytes(0.5 mol/L MgSO_(4);0.5 mol/L Na2SO_(4);0.5 mol/L MgSO_(4)+0.5 mol/L Na2SO_(4)).The composition structure and morphology of the surface of the samples were studied using scanning electron microscopy in combination with X-ray spectral microanalysis.The results of the experiments showed the formation of a surface film inhomogeneous in its structure and composition with the main components Mg(OH)_(2)and Mg O.An increase in the exposure time of the electrode in solution led to the formation of microcracks on the main film caused by internal stress because of hydration of magnesium oxide produced during corrosion.The salt composition of the electrolyte determines the morphology and thickness of corrosion films due to differences in the solubility of the products formed during the hydrolysis of magnesium oxide and the kinetics of this process.Applying the methods of scanning electron microscopy X-ray electron analysis gravimetry and voltammetry it has been established that at various stages of magnesium corrosion in different electrolytes the growth rates of corrosion films are determined by the kinetics of magnesium oxide formation its hydration and dissolution followed by crystallization in the form of a brucite phase of loose sediments on the surface.展开更多
Earthquake-induced gravity variation refers to changes in the earth’s gravity field associated with seismic activities.In recent years,development in the theories has greatly promoted seismic deformation research,lay...Earthquake-induced gravity variation refers to changes in the earth’s gravity field associated with seismic activities.In recent years,development in the theories has greatly promoted seismic deformation research,laying a solid theoretical foundation for the interpretation and application of seismological gravity monitoring.Traditional terrestrial gravity measurements continue to play a significant role in studies of interseismic,co-seismic,and post-seismic gravity field variations.For instance,superconducting gravimeter networks can detect co-seismic gravity change at the sub-micro Gal level.At the same time,the successful launch of satellite gravity missions(e.g.,the Gravity Recovery and Climate Experiment or GRACE)has also facilitated applied studies of the gravity variation associated with large earthquakes,and several remarkable breakthroughs have been achieved.The progress in gravity observation technologies(e.g.,GRACE and superconducting gravimetry)and advances in the theories have jointly promoted seismic deformation studies and raised many new research topics.For example,superconducting gravimetry has played an important role in analyses of episodic tremor,slow-slip events,and interseismic strain patterns;the monitoring of transient gravity signals and related theories have provided a new perspective on earthquake early warning systems;the mass transport detected by the GRACE satellites several months before an earthquake has brought new insights into earthquake prediction methods;the use of artificial intelligence to automatically identify tiny gravity change signals is a new approach to accurate and rapid determination of earthquake magnitude and location.Overall,many significant breakthroughs have been made in recent years,in terms of the theory,application,and observation measures.This article summarizes the progress,with the aim of providing a reference for seismologists and geodetic researchers studying the phenomenon of gravity variation,advances in related theories and applications,and future research directions in this discipline.展开更多
Instrumental and environmental disturbances do affect FG5 absolute gravimeter observations and the estimated gravity values, sometimes to the degree that entire measurement campaigns are discarded. We propose a method...Instrumental and environmental disturbances do affect FG5 absolute gravimeter observations and the estimated gravity values, sometimes to the degree that entire measurement campaigns are discarded. We propose a method which moves towards the re-assessment of previously discarded observations. Once an estimate of the frequency and amplitude of a disturbance in a FG5 data set exists, the proposed method can estimate its impact on the estimated gravity value. This is performed through a Gaussian Bell Summation approach of the functional relationship between disturbance frequency and standard deviation of gravity. The filtering of the identified disturbance is realized through a modification of the functional model of the equation of motion in the least squares adjustment of FG5 observations. The results reveal that the Gaussian Bell Summation approximates the frequency—gravity impact relationship sufficiently well with negligible uncertainties, while the accuracy of the detected disturbance frequency defines a limiting factor for the gravity impact estimation. A realistic disturbance of 15 Hz with an amplitude of 1.5 nm had an impact of ≈48 [μGal] on the gravity estimate. The proposed filter approach reduced the impact to ≈12 [μGal], with the remaining effect being almost entirely associated to the uncertainty in disturbance frequency detection.展开更多
<strong>Background</strong><span><span><span style="font-family:""><span style="font-family:Verdana;"><strong>: </strong>With newer protocols, s...<strong>Background</strong><span><span><span style="font-family:""><span style="font-family:Verdana;"><strong>: </strong>With newer protocols, such as delayed cord clamping, becoming routine practice, determining the potential maternal consequences is important. In particular, establishing normative values for blood loss from the hysterotomy would be helpful in addressing techniques to minimize total blood loss for cesarean deliveries. </span><b><span style="font-family:Verdana;">Objective</span></b><span style="font-family:Verdana;">: Blood loss from the hysterotomy during cesarean delivery has not been reported using quantitative methods. We aimed to quantify the rate of blood loss during cesarean delivery from the hysterotomy between creation and closure. </span><b><span style="font-family:Verdana;">Methods</span></b><span style="font-family:Verdana;">: This single center, prospective, case series was collected in 2018. Women with singleton pregnancies undergoing cesarean delivery at </span></span></span></span><span><span><span style="font-family:""><span style="font-family:Verdana;">≥</span><span><span style="font-family:Verdana;">37 0/7 weeks at Brigham and Women’s Hospital were included. Delayed cord clamping was performed which allowed for quantification of blood loss through gravimetric methods and descriptive statistics were performed. </span><b><span style="font-family:Verdana;">Results</span></b><span style="font-family:Verdana;">: Twenty patients were included. The mean hysterotomy closure delay for cord blood collection was 47 seconds (SD 10.2) and the mean maternal blood volume collected was 110.8 mL (SD 53.4 mL). Blood loss per minute was calculated with a median of 150 </span><span style="font-family:Verdana;">mL/minute (IQR 88.8 mL, 95% CI 109.2 - 190.4 mL). The mean post-operative </span><span style="font-family:Verdana;">hematocrit drop was 4.4%, and there were no blood transfusions. There was a single hysterotomy extension and a quantified blood loss of 413 mL per minute. </span><b><span style="font-family:Verdana;">Conclusion</span></b><span style="font-family:Verdana;">: We found a mean blood loss of 150 mL/min without hysterotomy extension. With a hysterotomy extension, the blood lost per minute was more profound. This normative data can be helpful for surgical planning with regards to delayed cord clamping or cord blood collection for banking.</span></span></span></span></span>展开更多
Temporal variations of atmospheric density distribution induce changes in the gravitational air mass attraction at a specific observation site. Additionally, the load of the atmospheric masses deforms the Earth’s cru...Temporal variations of atmospheric density distribution induce changes in the gravitational air mass attraction at a specific observation site. Additionally, the load of the atmospheric masses deforms the Earth’s crust and the sea surface. Variations in the local gravity acceleration and atmospheric pressure are known to be corrected with an admittance of about 3 nm/s2 per hPa as a standard factor, which is in accordance with the IAG Resolution No. 9, 1983. A more accurate admittance factor for a gravity station is varying with time and depends on the total global mass distribution within the atmosphere. The Institut für Erdmessung (IfE) performed absolute gravity observations in the Fennoscandian land uplift area nearly every year from 2003 to 2008. The objective is to ensure a reduction with 3 nm/s2 accuracy. Therefore, atmospheric gravity changes are modeled using globally distributed ECMWF data. The attraction effect from the local zone around the gravity station is calculated with ECMWF 3D weather data describing different pressure levels up to a height of 50 km. To model the regional and global attraction, and all deformation components the Green’s functions method and surface ECMWF 2D weather data are used. For the annually performed absolute gravimetry determinations, this approach improved the reductions by 8 nm/s2 (-19 nm/s2 to +4 nm/s2). The gravity modeling was verified using superconducting gravimeter data at station Membach inBelgiumimproving the residuals by about 15%.展开更多
Airborne gravimetry has become a vital technique in local gravity field approximation,and upward/downward continuation of gravity data is a key process of airborne gravimetry.In these procedures,the integral domain is...Airborne gravimetry has become a vital technique in local gravity field approximation,and upward/downward continuation of gravity data is a key process of airborne gravimetry.In these procedures,the integral domain is divided into two parts,namely the near-zone and the far-zone.The far-zone contributions are approximated by the truncation coefficients and a global geo-potential model,and their values are controlled by several issues.This paper investigates the effects of flight height,the size of near-zone cap,and RemoveCompute-Restore(RCR) technique upon far-zone contributions.Results show that at mountainous area the far-zone contributions can be ignored when EIGEN-6C of 360 degree is removed from the gravity data,together with a near-zone cap of 1° and a flight height less than 10 km,while at flat area EIGEN-6C of 180 degree is feasible.展开更多
In this study, a classic survey adjustment computation method was used for data obtained in the Inner Mongolia and Ningxia gravimetric networks between September 2013 and April 2015 so as to investigate the variation ...In this study, a classic survey adjustment computation method was used for data obtained in the Inner Mongolia and Ningxia gravimetric networks between September 2013 and April 2015 so as to investigate the variation of gravity before the Alxa Zuoqi M5.8 earthquake. The relationship between gravity variation and the Alxa Zuoqi M5.8 earthquake was analyzed. The results showed that:(1) the severe variation in gravity field at the test sites before the Alxa Zuoqi M5.8 earthquake, as well as the subsequent accelerated rising, might be an earthquake precursor;(2) the Alxa Zuoqi M5.8 earthquake occurred at the turning point where the high-gravity gradient zone changed from the NE direction to NW.展开更多
Gravity data associated with surface geology in the Northern Tunisian Atlas offer better understand to the underlying structures in Teboursouk area and to highlight other deep or unknown structures in surface. The gra...Gravity data associated with surface geology in the Northern Tunisian Atlas offer better understand to the underlying structures in Teboursouk area and to highlight other deep or unknown structures in surface. The gravity study was based on qualitative and quantitative analysis including the construction of the gravity Bouguer anomaly, upward continuations, residual anomaly, and Horizontal gradient maxima maps. The main results display many positive and negative anomalies as the response of geological structures (J. Cheid Triassic structure, Khalled plain, El Aroussa plain). In addition, the horizontal gradient maxima integrated with geological and structural maps let the identification of major directions of gravimetric lineaments in the study area us NE-SW trending features at the boundaries of J. Cheid structure, NW-SE direction that limit Gaafour plain and Tabet Ech Cherif syncline, and N-S trending that bordered El Aroussa basin. Major results allowed the construction of a new structural map of the study zone.展开更多
Only a causal class among the 199 Lorentzian ones, which do not exists in the Newtonian space-time, is privileged to construct a generic, gravity free and immediate (non retarded) relativistic positioning system. This...Only a causal class among the 199 Lorentzian ones, which do not exists in the Newtonian space-time, is privileged to construct a generic, gravity free and immediate (non retarded) relativistic positioning system. This is the causal class of the null emission coordinates. Emission coordinates are defined and generated by four emitters broadcasting their proper times. The emission coordinates are covariant (frame independent) and hence valid for any user. Any observer can obtain the values of his (her) null emission coordinates from the emitters which provide him his (her) position and trajectory.展开更多
Airborne particulate matter (PM) filter sample processing is susceptible to error and can present issues associated with organizing samples, tracking data, and maintaining weighing conditions. While filter weighing fa...Airborne particulate matter (PM) filter sample processing is susceptible to error and can present issues associated with organizing samples, tracking data, and maintaining weighing conditions. While filter weighing facilities should implement robust quality assurance and control checks to ensure that data collection is accurate and filter storage is secure, mistakes and accidents can still occur that compromise valuable data. This paper presents a novel approach to PM filter sample processing that allows for data validation or data recovery while ensuring data integrity. The technique approximates the original, unused pre-sampling weight of polytetrafluoroethylene (PTFE) filters after PM collection to determine PM mass-deposition (MD). The method describes the extraction of PM loaded on PTFE filters via sonication in relatively non-toxic solvents, methanol and distilled water. The extraction method is compared to the standard gravimetric PM MD determination method for a set of 265 PTFE filters with mean post-sampling filter mass of 116 ± 3.6 mg, mean estimated PM MD using the standard method of 367 ± 589 μg, and mean estimated PM MD using the extraction method of 371 ± 589 μg. A Deming regression comparison of the two methods yields a slope of 0.9983 and a Pearson’s r of 0.999. A Bland-Altman assessment of the percent and absolute differences between the two methods shows the limits of agreement between 32.5% and 25.5% and -61.9 and 50.1 μg, respectively. The 99% confidence interval of the mean difference in mass deposition between the two methods is -5.8 ± 4.5 μg. These data demonstrate that estimating pre-sampling PTFE filter mass by extracting PM from sampled filters is a viable technique for gravimetric filter analysis. This method is of use in recovering pre-sampling filter weights that have been lost, incorrectly measured, or otherwise compromised.展开更多
The south-east of Cameroon encompasses a wide variety of geological structures among which we can cite the Congo Craton (CC), the Sanaga Fault (SF), the Yaoundé Domain, the Panafrican belt, the Protozoic series a...The south-east of Cameroon encompasses a wide variety of geological structures among which we can cite the Congo Craton (CC), the Sanaga Fault (SF), the Yaoundé Domain, the Panafrican belt, the Protozoic series and the Dja complex. The presence of all these structures justifies the great tectonic activity to which this area was subject from the rupture of Pangea to the creation of the different plates that exist today. In this work, we will bring out a high-resolution structural map of the study area by applying the qualitative analysis of the phase filters on 200,900 points of gravimetric data obtained from the combination of the XGM2016 and ETOPO1 models. Then, with these same data, we will bring out another structural map with the maxima method called Multi-Scale Horizontal Derivative of Vertical Derivative (MSHDVD) which will be compared to the first in order to show the limits of the MSHDVD method. To do this, we will first use the extension method to highlight the map of residual anomalies, then a combination of derivative, gradient and phase filters to highlight the geological structures responsible for fracturing in this area. Phase filters have the advantage that they make it possible to highlight all the geological edges responsible for the fracturing without taking into account the depth, while the MSHDVD method highlights the existing geological contacts (edges) at depths well defined by the examiner. The structural map obtained with the MSHDVD method shows that the major structural direction in this zone is W-E while that obtained from the interpretation of the phase filters is more precise and shows that the major structural direction in this area would be N-S and this result would be in perfect agreement with the tectonics of East Cameroon.展开更多
This work presents the results of complex gravity observation performed at Shults Cape, Gamov peninsula (42.58°N, 131.15°E), Russia. Absolute laser gravimeter GABL type and Scintrex type relative gravimeter ...This work presents the results of complex gravity observation performed at Shults Cape, Gamov peninsula (42.58°N, 131.15°E), Russia. Absolute laser gravimeter GABL type and Scintrex type relative gravimeter were used for measurement. To investigate the accuracy of tidal corrections we compared the observed tidal parameters of the main tidal waves O1 and M2 with modeled ones computed from 6 different ocean tidal models: CSR4, FES02, FES04, GOT00, NAO99 and TPX06. After discussion a theoretical model based on TPX06 ocean tides model and DDW99 non hydrostatic body tides model was used for tidal correction of absolute gravity data. Preliminary estimate of gravity effect induced by the Tohoku-Oki earthquake of11 March 2011Mw = 9.0 at Primorye territory (Russia) was found to be 5.1 ± 2.0 μGal. Co-seismic crustal displacements revealed by GPS data at Far EastRussiacontinental coast are also investigated. Volumetric dilatation of this area is observed at +1.7 × 10-8 level.展开更多
基金Supported by the National Natural Science Foundation of China(Nos.42192535,41876136)the Guangdong Special Support Program(No.2019BT02H594)supported by the Key Special Projects of the Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)(for Introduced Talents Team)(Nos.GML2021GD0810,GML2019ZD0602)。
文摘To dampen periodic off-levelling motions within an inertial platform while undergoing horizontal accelerations of the same period and to achieve a levelling accuracy of a few tens of arcseconds with that system,an internally damped inertial platform for a marine scalar gravity system was the developed.Methods for attenuating horizontal acceleration and reducing off-levelling error by a satisfactory gyro-levelling loop,which are fundamental to the internally damped inertial platform,were designed and implemented.In addition,phase delays are introduced by the levelling loop.The resulting off-levelling gravity errors were analyzed and modeled.A series of tests on a motion simulator were performed in laboratory for a variety of simulated sea conditions.We found that the motion of the platform is a function of the amplitude and period of the simulated ship motions and ranges between 10 and 40 arcseconds.In addition,the phase lag between platform motion and ship motion is not constant but ranges 180°-270°,depending on the period and amplitude of the motion.Then,the platform,on which a gravimeter was mounted,was installed on the R/V Shiyan 2 to conduct a gravity survey in the South China Sea.Despite rough sea conditions,it was shown that in short periods of 2-30 s,the off-levelling angle was less than 30 arcseconds,and the phase lagged the horizontal acceleration by 230°-260°.From a repeated survey line and intersecting survey points,the estimated errors of gravity measurements were between 1.3 and 1.7 mGal.The marine measurements results were compared with those of satellite altimetry data and show a mean value of 0.5 mGal in a standard deviation of 1.5 mGal.
基金National Key R&D Program of China(No.2021YFB3900604)。
文摘The satellite gravimetry technology effectively recovers the global Earth’s gravity field.Since 2000s,HL-SST satellite CHAMP,LL-SST satellite GRACE,Gravity Gradient Measurement(GGM)satellite GOCE have been launched successfully,producing some Earth’s gravity models solely from satellites data.However,the space and time resolution of the Earth’s gravity fields do not adequately satisfy scientific objectives.The main reason is that the gravimetry satellites are not enough and observation data insufficient.The paper outlines the current and future status of Chinese gravity satellite missions.The Chinese gravimetry satellite system,named Chinese Gravimetry augment and Mass change exploring mission(ChiGaM),successfully launched in Dec.2021 after four years of production and over a year of calibration and valiation.The accelerometer,K-band ranging system and the three stellar sensors,among others,were precisely calibrated and trimmed.The satellite mass center was determined and coordinated with the proof center of accelerometer with an accuracy 100μm.The inter-satellite ranging system and BDS/GPS receiver operate together seamlessly.The range and range rate noise is less than 3μm/Hz^(1/2) and 1μm/s/Hz^(1/2),respectively,in band of 0.025~0.1 Hz.The electrostatic suspension accelerometer is working well.Its high-sensitive axis noise level is 3×10^(-10) m/s^(2)/Hz^(1/2)near the frequency 0.1 Hz,and 1×10^(-9) m/s^(2)/Hz^(1/2) for the less-sensitive axis.Meanwhile the BDS/GPS receiver is used to achieve data for precise orbit determination,yielding an orbit result with accuracy better than 2 cm.When compared with KBR observations,the RMS of the bias is less than 1 mm.Besides above mission,next gravimetric satellite is being developed now.TQ-2 mission is designed as a totally experimental satellite for gravitational wave detection at low Earth orbit,which can detect the Earth’s gravity field simultaneously.The Bender-type mission is considered the most promising configuration for TQ-2 and consists of two polar satellites and two inclined satellites.Due to the extra observations at the east-west direction derived from the inclined satellite pair,significant improvements has been made in detecting temporal signals with higher accuracy and spatial-temporal resolution.To achieve the scientific goal,the ACC MBW can shift from 0.001~0.1 Hz to 0.004~0.1 Hz for ACC,and the LRI MBW can shift from 0.01~1 Hz to 0.1~1 Hz.For future research,a gravimetric potential survey using cold-atomic-clock based on the general relativity theory,cold atom gradiometer should be pursued.Gravimetric technologies should be mined and researched,and the gravimetry satellite constellation should be developed,so as to improve the time resolution and space resolution for meeting the requirements of geophysics,geodesy,earthquake,water resources environment,oceanography,etc.
基金Open Fund of Hubei Luojia Laboratory(No.220100033)National Natural Science Foundation of China(Nos.42174108,42192535,42242015)。
文摘Gravity field is the most basic physical field generated by the material properties of the Earth system.It reflects the spatial distribution,movement and change of materials determined by the interaction and dynamic process inside the Earth.Over the years,a variety of technical means have been used to detect the Earth’s gravity field and supported numerous studies on the global change,resource detection,geological structure movement,water resources change and other related fields of research.Here is part of the progress in surface and marine gravimetry obtained by Chinese geodesy scientists from 2019 to 2023 from the following aspects,including:①Continuous gravity network in Chinese mainland;②Application of superconducting gravity measurement;③Network adjustment for continental-scale gravity survey campaign and data quality control;④Regional time-variable gravity field and its application;⑤Research progress on novel technologies for gravity inversion;⑥Research progress on marine gravity field determination;⑦Application research on marine gravity field.
文摘Natural gas (NG) is one of the most important sources of energy for industrial and domestic consumption in the present era because it is cheap and free from sulfur impurities. Therefore, accurate and precise measurement of its composition is of fundamental importance for trade reasons. To improve the quality of NG gas measurements, certified reference materials (CRMs) should be used for calibration of measuring equipment in order to ensure the traceability of the measurement results to the SI units. For the traceability purpose, a multicomponent natural gas mixture was prepared gravimetrically as a reference material according to ISO 6142 from pure helium, hydrogen, n-pentane, i-pentane, n-butane, i-butane, propane, ethane, hexane, methane and nitrogen. The preparation was done in two dilution steps in 5 L aluminum cylinders. The calculated mole fractions and associated uncertainties of natural gas components were verified by a dual GC-FID/TCD system in accordance with ISO 6143 calibrated by a series of primary gas mixtures (CRMs) produced by an NMI. The results obtained by gravimetry and by GC measurements have been checked for compatibility as required by ISO 6142 and were found in very good agreement. Details of the preparation and calculation of the mole fractions and uncertainties of all gas components are explained in this article.
基金supported by the Director Foundation of Institute of Seismology,China Earthquake Administration(Grant Nos:IS201726121)the National Natural Science Foundation of China(Grant Nos:41304059)the special earthquake research grant offered by China Earthquake Administration(Grant Nos:201308009,201508009)。
文摘Variation of terrestrial water storage in the Hebei plain area from March 2010 to June 2014 was studied using ground gravimetry combined with vertical displacement data from the Global Navigation Satellite System.Results show that observed gravity variation in this area increased continuously,basically reflecting a trend toward land subsidence.With the effect of this subsidence removed,a dominantnegative change in gravity variation was evident,reflecting an average rate of decrease in terrestrial water in this area of 0.10±0.053 m/y,and this is equivalent to a volume of 81.5±43.2×108 m^(3)and is consistent with the spatial distribution of groundwater change from measured hydrologic data.These results can be an essential reference and supplement for the study of terrestrial water variation in the Hebei plain area,and indicate that ground surface gravimetry can be used as an important mean for studying changes in terrestrial water.
基金The National Natural Science Foundation of China (41804011, 41706111)The National Major Development Program of China(2016YFC0303007,2016YFB0501704)+1 种基金The Great Scientific Instrument Development Project of China(2011YQ12004503)The National Basic Research Program of China(973 Program)(613219).
文摘Gravimetry technical guides are the scientific basis for air-sea gravimetry. However, the existing technical guides in China are behind the application requirements. This study analyzed the most important indicators of air-sea gravimetry, including the density of survey lines, gravimetry accuracy and space resolution, stability and reliability of the air-sea gravimeter, and proposed a gravimetry accuracy assessment system consisting of gravity RMS of error, systematic error and mean error, and an assessment system for the gravimeter stability consisting of the relative accuracy of the scale value, monthly zero-drift, RMS of the monthly nonlinear zero-drift variation and the threshold of the monthly nonlinear zero-drift variation. The mathematic models for the measurement point determination in shipborne gravimetry, E tv s correction for airborne gravimetry, platform tilt correction and evaluation air-sea gravimetry were also analyzed and modified. This work will provide technology support for the composition of the military-civil air-sea gravimetry technical guides.
基金supported by an NGA NURI grant.Leung’s research is partially supported by the RGC under Grant DAG09/10.SC02 and GRF602210supported by NSF 0810104.
文摘We propose a fast local level set method for the inverse problem of gravimetry.The theoretical foundation for our approach is based on the following uniqueness result:if an open set D is star-shaped or x3-convex with respect to its center of gravity,then its exterior potential uniquely determines the open set D.To achieve this purpose constructively,the first challenge is how to parametrize this open set D as its boundary may have a variety of possible shapes.To describe those different shapes we propose to use a level-set function to parametrize the unknown boundary of this open set.The second challenge is how to deal with the issue of partial data as gravimetric measurements are only made on a part of a given reference domainΩ.To overcome this difficulty,we propose a linear numerical continuation approach based on the single layer representation to find potentials on the boundary of some artificial domain containing the unknown set D.The third challenge is how to speed up the level set inversion process.Based on some features of the underlying inverse gravimetry problem such as the potential density being constant inside the unknown domain,we propose a novel numerical approach which is able to take advantage of these features so that the computational speed is accelerated by an order of magnitude.We carry out numerical experiments for both two-and three-dimensional cases to demonstrate the effectiveness of the new algorithm.
基金National Aeronautics and Space Ad-ministration(No.80NM0018D0004).
文摘A growing interest in small body exploration has motivated research into the rapid char-acterization of near-Earth objects to meet economic or scientific objectives.Specifically,knowledge of the internal density structure can aid with target selection and enables an understanding of prehistoric planetary formation to be developed.To this end,multi-layer extensions to the polyhedral gravity model are suggested,and an inversion technique is implemented to present their effectiveness.On-orbit gravity gradiometry is simulated and employed in stochastic and deterministic algorithms,with results that imply robustness in both cases.
文摘Studies have been conducted on the corrosive behavior of magnesium in aqueous sulfate electrolytes(0.5 mol/L MgSO_(4);0.5 mol/L Na2SO_(4);0.5 mol/L MgSO_(4)+0.5 mol/L Na2SO_(4)).The composition structure and morphology of the surface of the samples were studied using scanning electron microscopy in combination with X-ray spectral microanalysis.The results of the experiments showed the formation of a surface film inhomogeneous in its structure and composition with the main components Mg(OH)_(2)and Mg O.An increase in the exposure time of the electrode in solution led to the formation of microcracks on the main film caused by internal stress because of hydration of magnesium oxide produced during corrosion.The salt composition of the electrolyte determines the morphology and thickness of corrosion films due to differences in the solubility of the products formed during the hydrolysis of magnesium oxide and the kinetics of this process.Applying the methods of scanning electron microscopy X-ray electron analysis gravimetry and voltammetry it has been established that at various stages of magnesium corrosion in different electrolytes the growth rates of corrosion films are determined by the kinetics of magnesium oxide formation its hydration and dissolution followed by crystallization in the form of a brucite phase of loose sediments on the surface.
文摘Earthquake-induced gravity variation refers to changes in the earth’s gravity field associated with seismic activities.In recent years,development in the theories has greatly promoted seismic deformation research,laying a solid theoretical foundation for the interpretation and application of seismological gravity monitoring.Traditional terrestrial gravity measurements continue to play a significant role in studies of interseismic,co-seismic,and post-seismic gravity field variations.For instance,superconducting gravimeter networks can detect co-seismic gravity change at the sub-micro Gal level.At the same time,the successful launch of satellite gravity missions(e.g.,the Gravity Recovery and Climate Experiment or GRACE)has also facilitated applied studies of the gravity variation associated with large earthquakes,and several remarkable breakthroughs have been achieved.The progress in gravity observation technologies(e.g.,GRACE and superconducting gravimetry)and advances in the theories have jointly promoted seismic deformation studies and raised many new research topics.For example,superconducting gravimetry has played an important role in analyses of episodic tremor,slow-slip events,and interseismic strain patterns;the monitoring of transient gravity signals and related theories have provided a new perspective on earthquake early warning systems;the mass transport detected by the GRACE satellites several months before an earthquake has brought new insights into earthquake prediction methods;the use of artificial intelligence to automatically identify tiny gravity change signals is a new approach to accurate and rapid determination of earthquake magnitude and location.Overall,many significant breakthroughs have been made in recent years,in terms of the theory,application,and observation measures.This article summarizes the progress,with the aim of providing a reference for seismologists and geodetic researchers studying the phenomenon of gravity variation,advances in related theories and applications,and future research directions in this discipline.
文摘Instrumental and environmental disturbances do affect FG5 absolute gravimeter observations and the estimated gravity values, sometimes to the degree that entire measurement campaigns are discarded. We propose a method which moves towards the re-assessment of previously discarded observations. Once an estimate of the frequency and amplitude of a disturbance in a FG5 data set exists, the proposed method can estimate its impact on the estimated gravity value. This is performed through a Gaussian Bell Summation approach of the functional relationship between disturbance frequency and standard deviation of gravity. The filtering of the identified disturbance is realized through a modification of the functional model of the equation of motion in the least squares adjustment of FG5 observations. The results reveal that the Gaussian Bell Summation approximates the frequency—gravity impact relationship sufficiently well with negligible uncertainties, while the accuracy of the detected disturbance frequency defines a limiting factor for the gravity impact estimation. A realistic disturbance of 15 Hz with an amplitude of 1.5 nm had an impact of ≈48 [μGal] on the gravity estimate. The proposed filter approach reduced the impact to ≈12 [μGal], with the remaining effect being almost entirely associated to the uncertainty in disturbance frequency detection.
文摘<strong>Background</strong><span><span><span style="font-family:""><span style="font-family:Verdana;"><strong>: </strong>With newer protocols, such as delayed cord clamping, becoming routine practice, determining the potential maternal consequences is important. In particular, establishing normative values for blood loss from the hysterotomy would be helpful in addressing techniques to minimize total blood loss for cesarean deliveries. </span><b><span style="font-family:Verdana;">Objective</span></b><span style="font-family:Verdana;">: Blood loss from the hysterotomy during cesarean delivery has not been reported using quantitative methods. We aimed to quantify the rate of blood loss during cesarean delivery from the hysterotomy between creation and closure. </span><b><span style="font-family:Verdana;">Methods</span></b><span style="font-family:Verdana;">: This single center, prospective, case series was collected in 2018. Women with singleton pregnancies undergoing cesarean delivery at </span></span></span></span><span><span><span style="font-family:""><span style="font-family:Verdana;">≥</span><span><span style="font-family:Verdana;">37 0/7 weeks at Brigham and Women’s Hospital were included. Delayed cord clamping was performed which allowed for quantification of blood loss through gravimetric methods and descriptive statistics were performed. </span><b><span style="font-family:Verdana;">Results</span></b><span style="font-family:Verdana;">: Twenty patients were included. The mean hysterotomy closure delay for cord blood collection was 47 seconds (SD 10.2) and the mean maternal blood volume collected was 110.8 mL (SD 53.4 mL). Blood loss per minute was calculated with a median of 150 </span><span style="font-family:Verdana;">mL/minute (IQR 88.8 mL, 95% CI 109.2 - 190.4 mL). The mean post-operative </span><span style="font-family:Verdana;">hematocrit drop was 4.4%, and there were no blood transfusions. There was a single hysterotomy extension and a quantified blood loss of 413 mL per minute. </span><b><span style="font-family:Verdana;">Conclusion</span></b><span style="font-family:Verdana;">: We found a mean blood loss of 150 mL/min without hysterotomy extension. With a hysterotomy extension, the blood lost per minute was more profound. This normative data can be helpful for surgical planning with regards to delayed cord clamping or cord blood collection for banking.</span></span></span></span></span>
基金Within the R&D-Programme GEOTECHNOLOGIEN this study was funded by the German Ministry of Educa-tion and Research(BMBF)and the German Research Foundation(DFG),Grant Mu 1141/3-1 and 3-2.
文摘Temporal variations of atmospheric density distribution induce changes in the gravitational air mass attraction at a specific observation site. Additionally, the load of the atmospheric masses deforms the Earth’s crust and the sea surface. Variations in the local gravity acceleration and atmospheric pressure are known to be corrected with an admittance of about 3 nm/s2 per hPa as a standard factor, which is in accordance with the IAG Resolution No. 9, 1983. A more accurate admittance factor for a gravity station is varying with time and depends on the total global mass distribution within the atmosphere. The Institut für Erdmessung (IfE) performed absolute gravity observations in the Fennoscandian land uplift area nearly every year from 2003 to 2008. The objective is to ensure a reduction with 3 nm/s2 accuracy. Therefore, atmospheric gravity changes are modeled using globally distributed ECMWF data. The attraction effect from the local zone around the gravity station is calculated with ECMWF 3D weather data describing different pressure levels up to a height of 50 km. To model the regional and global attraction, and all deformation components the Green’s functions method and surface ECMWF 2D weather data are used. For the annually performed absolute gravimetry determinations, this approach improved the reductions by 8 nm/s2 (-19 nm/s2 to +4 nm/s2). The gravity modeling was verified using superconducting gravimeter data at station Membach inBelgiumimproving the residuals by about 15%.
基金supported by the National Natural Science Foundation of China (41504013,41174062)the Open Research Fund Program of the Key Laboratory of Geospace Environment and Geodesy,Ministry of Education,China (14-01-03)the Doctoral Scientific Research Foundation of Guangdong University of Technology(253151010)
文摘Airborne gravimetry has become a vital technique in local gravity field approximation,and upward/downward continuation of gravity data is a key process of airborne gravimetry.In these procedures,the integral domain is divided into two parts,namely the near-zone and the far-zone.The far-zone contributions are approximated by the truncation coefficients and a global geo-potential model,and their values are controlled by several issues.This paper investigates the effects of flight height,the size of near-zone cap,and RemoveCompute-Restore(RCR) technique upon far-zone contributions.Results show that at mountainous area the far-zone contributions can be ignored when EIGEN-6C of 360 degree is removed from the gravity data,together with a near-zone cap of 1° and a flight height less than 10 km,while at flat area EIGEN-6C of 180 degree is feasible.
基金supported by the China Earthquake Administration Earthquake Tracking Task Orientation(2016020202,2016010216,and 2016010220)the“Three Combination”project of the China Earthquake Administration(163201)+2 种基金the National Natural Science Foundation of China(41204058,41474064,and 41374088)the special earthquake research,China Earthquake Administration(201508009-08)the Director,Foundation of Institute of Seismology,China Earthquake Administration(IS201326123)
文摘In this study, a classic survey adjustment computation method was used for data obtained in the Inner Mongolia and Ningxia gravimetric networks between September 2013 and April 2015 so as to investigate the variation of gravity before the Alxa Zuoqi M5.8 earthquake. The relationship between gravity variation and the Alxa Zuoqi M5.8 earthquake was analyzed. The results showed that:(1) the severe variation in gravity field at the test sites before the Alxa Zuoqi M5.8 earthquake, as well as the subsequent accelerated rising, might be an earthquake precursor;(2) the Alxa Zuoqi M5.8 earthquake occurred at the turning point where the high-gravity gradient zone changed from the NE direction to NW.
文摘Gravity data associated with surface geology in the Northern Tunisian Atlas offer better understand to the underlying structures in Teboursouk area and to highlight other deep or unknown structures in surface. The gravity study was based on qualitative and quantitative analysis including the construction of the gravity Bouguer anomaly, upward continuations, residual anomaly, and Horizontal gradient maxima maps. The main results display many positive and negative anomalies as the response of geological structures (J. Cheid Triassic structure, Khalled plain, El Aroussa plain). In addition, the horizontal gradient maxima integrated with geological and structural maps let the identification of major directions of gravimetric lineaments in the study area us NE-SW trending features at the boundaries of J. Cheid structure, NW-SE direction that limit Gaafour plain and Tabet Ech Cherif syncline, and N-S trending that bordered El Aroussa basin. Major results allowed the construction of a new structural map of the study zone.
文摘Only a causal class among the 199 Lorentzian ones, which do not exists in the Newtonian space-time, is privileged to construct a generic, gravity free and immediate (non retarded) relativistic positioning system. This is the causal class of the null emission coordinates. Emission coordinates are defined and generated by four emitters broadcasting their proper times. The emission coordinates are covariant (frame independent) and hence valid for any user. Any observer can obtain the values of his (her) null emission coordinates from the emitters which provide him his (her) position and trajectory.
文摘Airborne particulate matter (PM) filter sample processing is susceptible to error and can present issues associated with organizing samples, tracking data, and maintaining weighing conditions. While filter weighing facilities should implement robust quality assurance and control checks to ensure that data collection is accurate and filter storage is secure, mistakes and accidents can still occur that compromise valuable data. This paper presents a novel approach to PM filter sample processing that allows for data validation or data recovery while ensuring data integrity. The technique approximates the original, unused pre-sampling weight of polytetrafluoroethylene (PTFE) filters after PM collection to determine PM mass-deposition (MD). The method describes the extraction of PM loaded on PTFE filters via sonication in relatively non-toxic solvents, methanol and distilled water. The extraction method is compared to the standard gravimetric PM MD determination method for a set of 265 PTFE filters with mean post-sampling filter mass of 116 ± 3.6 mg, mean estimated PM MD using the standard method of 367 ± 589 μg, and mean estimated PM MD using the extraction method of 371 ± 589 μg. A Deming regression comparison of the two methods yields a slope of 0.9983 and a Pearson’s r of 0.999. A Bland-Altman assessment of the percent and absolute differences between the two methods shows the limits of agreement between 32.5% and 25.5% and -61.9 and 50.1 μg, respectively. The 99% confidence interval of the mean difference in mass deposition between the two methods is -5.8 ± 4.5 μg. These data demonstrate that estimating pre-sampling PTFE filter mass by extracting PM from sampled filters is a viable technique for gravimetric filter analysis. This method is of use in recovering pre-sampling filter weights that have been lost, incorrectly measured, or otherwise compromised.
文摘The south-east of Cameroon encompasses a wide variety of geological structures among which we can cite the Congo Craton (CC), the Sanaga Fault (SF), the Yaoundé Domain, the Panafrican belt, the Protozoic series and the Dja complex. The presence of all these structures justifies the great tectonic activity to which this area was subject from the rupture of Pangea to the creation of the different plates that exist today. In this work, we will bring out a high-resolution structural map of the study area by applying the qualitative analysis of the phase filters on 200,900 points of gravimetric data obtained from the combination of the XGM2016 and ETOPO1 models. Then, with these same data, we will bring out another structural map with the maxima method called Multi-Scale Horizontal Derivative of Vertical Derivative (MSHDVD) which will be compared to the first in order to show the limits of the MSHDVD method. To do this, we will first use the extension method to highlight the map of residual anomalies, then a combination of derivative, gradient and phase filters to highlight the geological structures responsible for fracturing in this area. Phase filters have the advantage that they make it possible to highlight all the geological edges responsible for the fracturing without taking into account the depth, while the MSHDVD method highlights the existing geological contacts (edges) at depths well defined by the examiner. The structural map obtained with the MSHDVD method shows that the major structural direction in this zone is W-E while that obtained from the interpretation of the phase filters is more precise and shows that the major structural direction in this area would be N-S and this result would be in perfect agreement with the tectonics of East Cameroon.
文摘This work presents the results of complex gravity observation performed at Shults Cape, Gamov peninsula (42.58°N, 131.15°E), Russia. Absolute laser gravimeter GABL type and Scintrex type relative gravimeter were used for measurement. To investigate the accuracy of tidal corrections we compared the observed tidal parameters of the main tidal waves O1 and M2 with modeled ones computed from 6 different ocean tidal models: CSR4, FES02, FES04, GOT00, NAO99 and TPX06. After discussion a theoretical model based on TPX06 ocean tides model and DDW99 non hydrostatic body tides model was used for tidal correction of absolute gravity data. Preliminary estimate of gravity effect induced by the Tohoku-Oki earthquake of11 March 2011Mw = 9.0 at Primorye territory (Russia) was found to be 5.1 ± 2.0 μGal. Co-seismic crustal displacements revealed by GPS data at Far EastRussiacontinental coast are also investigated. Volumetric dilatation of this area is observed at +1.7 × 10-8 level.
