Journal articles on the topic 'Gravity variations'

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1

Kumari, Pooja, V. Raghunandan, and P. Biswal. "Diurnal variation in aviation significant gravity-dependent and gravity-independent anthropometric parameters." Indian Journal of Aerospace Medicine 65 (August 6, 2021): 5–9. http://dx.doi.org/10.25259/ijasm_61_2020.

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Introduction: Anthropometric parameters need to be accurately measured because of their direct implications in selection of aircrew, aircrew-cockpit compatibility, and cockpit workspace design. Some of these parameters have significant diurnal variation, hence, measurement of these parameters in particular time of day becomes important. Quantification of these diurnal variations among some of the aviation significant parameters was the desired objective of the study. Material and Methods: In a prospective repeated measure design, anthropometric parameters of a total of 35 volunteers were measured in the standard defined protocol from 0800h to 1600h, at an interval of every 2h, using Institute of Aerospace Medicine (IAM) Anthropometry Platform. The data were analyzed to observe and quantify changes in diurnal variations in both gravity-dependent and gravity-independent parameters. A maximum value of 0.4 cm was taken as intraobserver variations based on the results of a pilot study. Results: There was a statistically significant decrement in the values of gravity-dependent anthropometric parameters from morning to evening; the difference being more after 1200h. Most of the gravity-independent parameters did not show any significant changes from 0800h to 1600h, except leg length, which showed a decrement overtime, the difference being statistically significant after 1200h. Conclusion: The study revealed a statistically significant variation of gravity-dependent anthropometric parameters from the baseline which could be because of the effect of erect posture on the intervertebral disc height and axial compressive loads on the spine. This became practically significant after 1200h. However, most of the gravity-independent parameters did not show any significant variations. Based on the results of this study, anthropometric measurements should be done in the morning hours preferably before 1200h.
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2

LaFehr, T. R. "Standardization in gravity reduction." GEOPHYSICS 56, no. 8 (August 1991): 1170–78. http://dx.doi.org/10.1190/1.1443137.

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Gravity reduction standards are needed to improve anomaly quality for interpretation and to facilitate the joining together of different data sets. To the extent possible, data reduction should be quantitative, objective, and comprehensive, leaving ambiguity only to the interpretation process that involves qualitative, subjective, and geological decisions. The term (Bouguer anomaly) describes a field intended to be free of all nongeologic effects—not modified by a partial geologic interpretation. Measured vertical gradients of gravity demonstrate considerable variation but do not suggest, as often reported, that the normal free‐air gradient is in error or needs to be locally adjusted. Such gradients are strongly influenced by terrain and, to a lesser extent, by the same geologic sources which produce Bouguer anomalies. A substantial body of existing literature facilitates the comprehensive treatment of terrain effects, which may be rigorously implemented with current computer technology. Although variations in topographic rock density are a major source of Bouguer anomalies, a constant density appropriate to the area under investigation is normally adopted as a data reduction standard, leaving a treatment of the density variations to the interpretation. A field example from British Columbia illustrates both the variations in vertical gravity gradients which can be encountered and the conclusion that the classical approach to data reduction is practically always suitable to account for the observed effects. Standard data reduction procedures do not (and should not) include reduction‐to‐datum. The interpreter must be aware, however, that otherwise “smooth” regional Bouguer anomalies caused by regional sources do contain high‐frequency components in areas of rugged topography.
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3

Dumberry, Mathieu. "Gravity variations induced by core flows." Geophysical Journal International 180, no. 2 (February 2010): 635–50. http://dx.doi.org/10.1111/j.1365-246x.2009.04437.x.

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4

Kuo, John T., and Sun Yue-Feng. "Modeling gravity variations caused by dilatancies." Tectonophysics 227, no. 1-4 (November 1993): 127–43. http://dx.doi.org/10.1016/0040-1951(93)90091-w.

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5

Clemesha, B. R., P. P. Batista, R. A. Buriti da Costa, and N. Schuch. "Seasonal variations in gravity wave activity at three locations in Brazil." Annales Geophysicae 27, no. 3 (March 4, 2009): 1059–65. http://dx.doi.org/10.5194/angeo-27-1059-2009.

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Abstract. Using the variance in meteor radar winds as a measure of gravity wave activity, we investigate the temporal variations in gravity waves at three locations in Brazil: São João do Cariri (7.3° S, 36.4° W), Cachoeira Paulista (22.7° S, 45.0° W) and Santa Maria (29.7° S, 53.7° W). The technique used is that of Hocking (2005) which makes it possible to separate the zonal and meridional components of the fluctuating wind velocity. We find that the seasonal variation of the fluctuating wind is similar to that of the amplitude of the diurnal tide, showing a predominantly semi-annual variation, stronger at Cachoeira Paulista and Santa Maria than at the quasi-equatorial station, Cariri. Both with respect to the seasonal trend and shorter term variations, strong coupling between gravity wave activity and tides is indicated by a remarkably close correlation between the fluctuating velocity and the vertical shear in the tidal winds. It is not clear as to whether this is caused by gravity wave forcing of the tides or whether it results from in situ generation of gravity waves by tidal wind shear.
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6

Journal, Baghdad Science. "Gravity Field Interpretation for Major Fault Depth Detection in a Region Located SW- Qa’im / Iraq." Baghdad Science Journal 14, no. 3 (September 3, 2017): 625–36. http://dx.doi.org/10.21123/bsj.14.3.625-636.

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This research deals with the qualitative and quantitative interpretation of Bouguer gravity anomaly data for a region located to the SW of Qa’im City within Anbar province by using 2D- mapping methods. The gravity residual field obtained graphically by subtracting the Regional Gravity values from the values of the total Bouguer anomaly. The residual gravity field processed in order to reduce noise by applying the gradient operator and 1st directional derivatives filtering. This was helpful in assigning the locations of sudden variation in Gravity values. Such variations may be produced by subsurface faults, fractures, cavities or subsurface facies lateral variations limits. A major fault was predicted to extend with the direction NE-SW. This fault is mentioned by previous studies as undefined subsurface fault depth within the sedimentary cover rocks. The results of this research that were obtained by gravity quantitative interpretation find that the depth to this major fault plane center is about 2.4 Km.
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7

Ruggiero, Matteo Luca. "Perturbations of Keplerian orbits in stationary spherically symmetric spacetimes." International Journal of Modern Physics D 23, no. 05 (April 30, 2014): 1450049. http://dx.doi.org/10.1142/s0218271814500497.

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We study spherically symmetric perturbations determined by alternative theories of gravity to the gravitational field of a central mass in General Relativity (GR). In particular, we focus on perturbations in the form of power laws and calculate their effect on the secular variations of the orbital elements of a Keplerian orbit. We show that, to lowest approximation order, only the argument of pericenter and mean anomaly undergo secular variations; furthermore, we calculate the variation of the orbital period. We give analytic expressions for these variations which can be used to constrain the impact of alternative theories of gravity.
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8

Földváry, Lorant, Victor Statov, and Nizamatdin Mamutov. "Applicability of GRACE and GRACE-FO for monitoring water mass changes of the Aral Sea and the Caspian Sea." InterCarto. InterGIS 26, no. 2 (2020): 443–53. http://dx.doi.org/10.35595/2414-9179-2020-2-26-443-453.

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The GRACE gravity satellite mission has provided monthly gravity field solutions for about 15 years enabling a unique opportunity to monitor large scale mass variation processes. By the end of the GRACE, the GRACE-FO mission was launched in order to continue the time series of monthly gravity fields. The two missions are similar in most aspects apart from the improved intersatellite range rate measurements, which is performed with lasers in addition to microwaves. An obvious demand for the geoscientific applications of the monthly gravity field models is to understand the consistency of the models provided by the two missions. This study provides a case-study related consistency investigation of GRACE and GRACE-FO monthly solutions for the Aral Sea region. As the closeness of the Caspian Sea may influence the monthly mass variations of the Aral Sea, it has also been involved in the investigations. According to the results, GRACE-FO models seem to continue the mass variations of the GRACE period properly, therefore their use jointly with GRACE is suggested. Based on the justified characteristics of the gravity anomaly by water volume variations in the case of the Aral Sea, GRACE models for the period March–June 2017 are suggested to be neglected. Though the correlation between water volume and monthly gravity field variations is convincing in the case of the Aral Sea, no such a correlation for the Caspian Sea could have been detected, which suggests to be the consequence of other mass varying processes, may be related to the seismicity of the Caspian Sea area.
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9

Ridley, Kevin. "Modelling the Gravitational Effects of Random Underground Density Variations." Mathematical Geosciences 52, no. 6 (October 9, 2019): 759–81. http://dx.doi.org/10.1007/s11004-019-09827-3.

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Abstract A mathematical model for small-scale spatial variations in gravity above the Earth’s surface is presented. Gravity variations are treated as a Gaussian random process arising from underground density variations which are assumed to be a Gaussian random process. Expressions for two-point spatial statistics are calculated for both the vertical component of gravity and the vertical gradient of the vertical component. Results are given for two models of density variations: a delta-correlated model and a fractal model. The effect of an outer scale in the fractal model is investigated. It is shown how the results can be used to numerically generate realisations of gravity variations with fractal properties. Such numerical modelling could be useful for investigating the feasibility of using gravity surveys to locate and characterise underground structures; this is explored through the simple example of a tunnel detection scenario.
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10

Goodkind, John M. "Continuous measurement of nontidal variations of gravity." Journal of Geophysical Research 91, B9 (1986): 9125. http://dx.doi.org/10.1029/jb091ib09p09125.

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11

Shum, C. K., and R. J. Eanes. "Time variations in the Earth's gravity fields." Eos, Transactions American Geophysical Union 73, no. 3 (1992): 33. http://dx.doi.org/10.1029/91eo00031.

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12

Boy, Jean-Paul, Richard Ray, and Jacques Hinderer. "Diurnal atmospheric tide and induced gravity variations." Journal of Geodynamics 41, no. 1-3 (January 2006): 253–58. http://dx.doi.org/10.1016/j.jog.2005.10.010.

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13

Hirota, I. "Seasonal and latitudinal variations of gravity waves." Advances in Space Research 10, no. 12 (January 1990): 103–9. http://dx.doi.org/10.1016/0273-1177(90)90389-h.

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14

Antonov, Yu V. "ABOUT A POSSIBLE CONNECTION BETWEEN EARTHQUAKES AND LUNAR-SOLAR GRAVITY VARIATIONS." Proceedings of higher educational establishments. Geology and Exploration, no. 3 (June 25, 2018): 51–57. http://dx.doi.org/10.32454/0016-7762-2018-3-51-57.

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A possible correlation between the destructive earthquakes of magnitude M = 7 and above and luni-solar gravity variations between 1975 and 2015 has been analyzed. The lunar-solar variations are characterized by three extreme points: the maximum and minimum values of gravity, and the maximum rate of change of variations. At this time, there is an extreme impact of lunar-solar attraction on the earth’s crust and the Earth as a whole. Variations can be a source of irreversible deformation in the earth’s crust. If in this case, there is an additional external impact of space factors, the probability of an earthquake is increased. In a time, the earthquakes are grouped near extremes of lunar-solar variations: half of the events are associated with the maximum gradient of variations change, and the second half is equally confined to the maximum and minimum value of gravity variations. Lunar-solar variations of gravity in conjunction with other cosmic influences can cause earthquakes.
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15

Nurul, Muhammad, Syamsurijal Rasimeng, Ida Bagus Suananda Yogi, Aprillia Yulianata, and Aisah Yuliantina. "FORWARD MODELLING METODE GAYABERAT DENGAN MODEL INTRUSI DAN PATAHAN MENGGUNAKAN OCTAVE." JURNAL GEOCELEBES 4, no. 2 (September 23, 2020): 111–17. http://dx.doi.org/10.20956/geocelebes.v4i2.10112.

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The gravity method is a geophysical exploration method to measure variations in the acceleration of gravity on the surface of the earth in response to variations in rocks that exist beneath the surface. In gravity exploration requires a preliminary picture as a reference for measurement. This study aims to make forward modeling synthetic OCTAVE based using synthetic data on subsurface rock structures, so as to produce intrusion and fracture models based on differences in the value of the acceleration of gravity from one point to another on the surface of the earth. Synthetic modeling with the geological parameter approach of the study area is based on variations in the price of rock density. The model parameters used in intrusion modeling are the density value of 2.7 g/cm3 and the depth of 850 meters while the fracture modeling uses a density value of 2.7 g/cm3 with a depth of 350 meters and 360 meters and a thickness of 500 meters. From intrusion modeling, the gravity vertical component of attraction force is 0.03 mGal and in the fracture modeling the gravity vertical component of attraction force is 0.0565 mGal. Based on the results of this modeling, distance curve vs. gravity anomaly response is obtained for both cases. In the intrusion rock model obtained by the profile model with an open type down. While the fracture modeling is obtained anomalous profile curve variation which states that in the fracture area with a significant change in the direction of the curve.
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16

Antonov, YU V. "ABNORMAL CHANGES OF THE NON-TIDAL VARIATIONS OF GRAVITY." Proceedings of higher educational establishments. Geology and Exploration, no. 2 (April 28, 2017): 70–76. http://dx.doi.org/10.32454/0016-7762-2017-2-70-76.

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Non-tidal variations of gravity are the residual part of the monitoring of the variations after subtraction from them the lunar-solar gravity variations and the drift of the zero point of the gravimeter. Non-tidal variations are sometimes of complex morphology and structure. The sources of the non-tidal variations are the intracrustal processes and flows of the charged particles in space. The streams of the charged particles can affect the sensor of the gravimeter. The streams of the charged particles can create a powerful magnetic hydrodynamic (MHD) shocks that cause abnormal changes of gravity. It is necessary to consider the non-tidal variations when carrying out high-precision gravimetric measurements.
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17

Timmen, Ludger, Christian Gerlach, Till Rehm, Christof Völksen, and Christian Voigt. "Geodetic-Gravimetric Monitoring of Mountain Uplift and Hydrological Variations at Zugspitze and Wank Mountains (Bavarian Alps, Germany)." Remote Sensing 13, no. 5 (March 1, 2021): 918. http://dx.doi.org/10.3390/rs13050918.

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In 2004, first absolute gravity (AG) measurements were performed on the top of Mt. Zugspitze (2 sites) and at the foot (1 site) and top (1 site) of Mt. Wank. Mt. Wank (summit height 1780 m) and Mt. Zugspitze (2960 m) are about 15 km apart from each other and belong geologically to different parts of the Northern Limestone Alps. Bridging a time span of 15 years, the deduced gravity variations for Zugspitze are in the order of −0.30 μm/s2 with a standard uncertainty of 0.04 μm/s2. The Wank stations (foot and top) show no significant gravity variation. The vertical stability of Wank summit is also confirmed by results of continuous GNSS recordings. Because an Alpine mountain uplift of 1 or 2 mm/yr cannot explain the obtained gravity decline at Zugspitze, the dominating geophysical contributions are assumed to be due to the diminishing glaciers in the vicinity. The modelled gravity trend caused by glacier retreat between epochs 1999 and 2018 amounts to −0.012 μm/s2/yr at both Zugspitze AG sites. This explains more than half of the observed gravity decrease. Long-term variations on inter-annual and climate-relevant decadal scale will be investigated in the future using as supplement superconducting gravimetry (installed in 2019) and GNSS equipment (since 2018).
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18

Van Hoolst, T., V. Dehant, F. Roosbeek, and P. Lognonné. "Tidally induced surface displacements, external potential variations, and gravity variations on Mars." Icarus 161, no. 2 (February 2003): 281–96. http://dx.doi.org/10.1016/s0019-1035(02)00045-3.

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19

Dimitrijevic, Ivan, Branko Dragovich, Jelena Grujic, and Zoran Rakic. "Some cosmological solutions of a nonlocal modified gravity." Filomat 29, no. 3 (2015): 619–28. http://dx.doi.org/10.2298/fil1503619d.

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We consider nonlocal modification of the Einstein theory of gravity in framework of the pseudo- Riemannian geometry. The nonlocal term has the form H(R)F(?)G(R), where H and G are differentiable functions of the scalar curvature R, and F(?) = ??n=0 fn?n is an analytic function of the d?Alambert operator ?. Using calculus of variations of the action functional, we derived the corresponding equations of motion. The variation of action is induced by variation of the gravitational field, which is the metric tensor g?v. Cosmological solutions are found for the case when the Ricci scalar R is constant.
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20

Cooper, A. P. R., and M. R. Gorman. "Investigating variations in the gravitational constant." Polar Record 25, no. 152 (January 1989): 55–58. http://dx.doi.org/10.1017/s0032247400009992.

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AbstractIn August–September 1987 a group of geophysicists, led by M. Ander of the Los Alamos National Laboratory and M. Zumberge of Scripps Institution of Oceanography, performed a geophysical experiment to determine the value of the gravitational constant, G. Using the DYE-3 borehole on the Greenland ice cap, the experiment was intended to provide evidence concerning possible scale variations in G, and thus for non-Newtonian gravity. This report describes the background to the experiment and the radio echo-sounding survey carried out to provide terrain corrections for the gravity model. The experiment showed values of G differing from laboratory determinations by margins which considerably exceed experimental error.
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Zhang, Min, Ziwei Liu, Qiong Wu, Yuntian Teng, Xiaotong Zhang, Feibai Du, and Ying Jiang. "Hydrologic changes of in-situ gravimetry." GEOPHYSICS 87, no. 2 (February 10, 2022): B117—B127. http://dx.doi.org/10.1190/geo2021-0037.1.

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Inter-seasonal and geodynamics-related gravity changes are important geoscientific signals that are extractable from gravimeter observations after removing background information as local hydrology gravity effect. With two superconducting gravimeters (SGs: OSG-053 and iGrav-007) located in different tectonic units, continuous global navigation satellite system data and absolute gravity observations, Wuhan, China, is an ideal location for investigating the effects of gravity resulting from significant local hydrology mass variations. We have processed approximately 26 months of gravity data collected from the SGs in Wuhan and obtained residuals of [Formula: see text] for OSG-053 and [Formula: see text] for iGrav-007. The hydrological observations indicate an estimated gravity increase of [Formula: see text] near iGrav-007, which mainly results from an increase in unconfined water level with an aquifer-specific yield of approximately 0.1. However, the gravity changes around OSG-053 are mainly from soil moisture and reach −[Formula: see text]. The soil type, thickness, and water content parameters are obtained from hydrogeological surveys and drilling data. The deep confined water level rises by 2.5 m, which introduces a [Formula: see text] gravity variation with a specific storage approximately 0.00001 from the field unsteady-flow pumping test. The modeled gravity is approximately [Formula: see text] around OSG-053 and [Formula: see text] around iGrav-007, in accordance with the observed gravity variations. The difference in gravity changes between the two SG observations can be explained by different local water storage environments. Our results suggest that unconfined and soil water significantly impact the in-situ gravimetry, and that further detailed hydrogeological surveys are required. A combined investigation of gravity and water levels can be a useful approach for monitoring aquifer storage conditions and groundwater management.
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22

Vishalakshi, T. N., and G. Chandra Shekara. "EFFECT OF AN APPLIED MAGNETIC FIELD AND GRAVITY MODULATION ON THE TIME DEPENDENT HYDRO-MAGNETIC INSTABILITY." Advances in Mathematics: Scientific Journal 10, no. 1 (January 20, 2021): 391–401. http://dx.doi.org/10.37418/amsj.10.1.39.

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In this present study a linear hydro-magnetic instability of time-dependent convection is designed and analyzed by using extended Stuart-Davis technique. The time variations are applied by fluctuating the fluid layer in the direction perpendicular to the flow and also the gravity modulation is introduced as sine and exponential function of time is considered to be one of the important effect. The extended Stuart-Davis technique is applied in tackling the time-dependency. To understand the effect of applied magnetic field and gravity modulation on the convection is analyzed with respect to different values of Chandrasekhar's number. The results shows that the magnetic field is having stabilizing impact in case of sinusoidal variation gravity field on the contrast it as destabilizing impact in case of exponential variation of gravity for short time but in long run it is having stabilizing effect.
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23

Sharaf, M. A., and Z. A. Mominkhan. "Gravity Variations in the Kingdom of Saudi Arabia." JOURNAL OF ADVANCES IN MATHEMATICS 11, no. 7 (November 7, 2015): 5382–87. http://dx.doi.org/10.24297/jam.v11i7.1215.

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The class of life distributions used better than aged in convex order upper tail ordering (UBACT) is introduced. A Moment inequality to this class (UBACT) of life distribution is given. In addition testing exponentiality versus (UBACT) class of life distribution based on a moment inequality is presented. Simulation such as critical values, Pitmans asymptotic efficiency and the power of test are discussed. Medical applications are given at the end of the paper.
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24

Nerem, R. S. "Progress made in studying variations of Earth's gravity." Eos, Transactions American Geophysical Union 75, no. 7 (1994): 76. http://dx.doi.org/10.1029/94eo00704.

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25

Meurers, Bruno. "Investigation of temporal gravity variations in SG-records." Journal of Geodynamics 38, no. 3-5 (October 2004): 423–35. http://dx.doi.org/10.1016/j.jog.2004.07.011.

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Crossley, David, Jacques Hinderer, and Jean-Paul Boy. "Regional gravity variations in Europe from superconducting gravimeters." Journal of Geodynamics 38, no. 3-5 (October 2004): 325–42. http://dx.doi.org/10.1016/j.jog.2004.07.014.

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27

Doi, Koichiro, Kazuo Shibuya, Anja Wendt, Reinhard Dietrich, and Matt King. "Tidal gravity variations revisited at Vostok Station, Antarctica." Polar Science 3, no. 1 (June 2009): 1–12. http://dx.doi.org/10.1016/j.polar.2008.11.001.

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28

Marzuoli, Annalisa, and Dario Merzi. "Conformal variations and quantum fluctuations in discrete gravity." International Journal of Geometric Methods in Modern Physics 13, no. 06 (June 15, 2016): 1650084. http://dx.doi.org/10.1142/s0219887816500845.

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After an overview of variational principles for discrete gravity, and on the basis of the approach to conformal transformations in a simplicial PL setting proposed by Luo and Glickenstein, we present at a heuristic level an improved scheme for addressing the gravitational (Euclidean) path integral and geometrodynamics.
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Liang, Weifeng, Guoqing Zhang, Yiqing Zhu, Yunma Xu, Shusong Guo, Yunfeng Zhao, Fang Liu, and Lingqiang Zhao. "Gravity variations before the Menyuan Ms 6.4 earthquake." Geodesy and Geodynamics 7, no. 4 (July 2016): 223–29. http://dx.doi.org/10.1016/j.geog.2016.04.013.

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30

Kravchenko, Yu A. "The lunar influence on the vertical deflections and gravity variations." Geodesy and Cartography 928, no. 10 (November 20, 2017): 2–9. http://dx.doi.org/10.22389/0016-7126-2017-928-10-2-9.

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The increase of building complexity causes the raise of requirements for accuracy of geodetic observations and the necessity to revise the variety of factors influencing the measurement results. Such factors include the lunar influence on the gravity intensity and direction. The necessity of correcting geodetic observations by the lunar influence and estimation of their highest influence on the Earth gravity and vertical deflections are outlined. The results obtained from the computational experiment on extreme values estimation of vertical deflections (up to 1''), variations of measured heights (up to 0,5 mm by 100 m) and gravity variations (up to 5,44 × 10^(-5) m∙kg / с^2) are sufficient to modify the existing techniques for precision leveling and gravity observations. Another argument in favor of the need to take into account the Moon influence and other factors is the accuracy increase of geodetic instruments (levels and gravimeters).Without changing the method of performing high-precision leveling and gravity measurements and entering the necessary corrections, real accuracy increase of these works can not be achieved. In this case, the ideas about the accuracy achieved, for example, when it is estimated by internal convergence, will be overestimated.
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31

Попов, А., A. Popov, Николай Гаврилов, Nikolay Gavrilov, А. Андреев, A. Andreev, Александр Погорельцев, and Aleksandr Pogoreltsev. "Interannual dynamics in intensity of mesoscale hydroxyl nightglow variations over Almaty." Solar-Terrestrial Physics 4, no. 2 (June 29, 2018): 63–68. http://dx.doi.org/10.12737/stp-42201810.

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The method of digital difference filters is applied to the data analysis of SATI observations of hydroxyl nightglow intensity and rotational temperature at altitudes 85–90 km over Almaty (43°03' N, 76°58' E), Kazakhstan, in 2010–2017. We examine seasonal and interannual variations in monthly average values and standard deviations of variations with periods 0.4–5.4 hrs, which may be associated with internal gravity waves in the mesopause region. The monthly average temperature near the mesopause has a maximum in winter and a minimum in June. The monthly average intensity has an additional maximum in June. Standard deviation of mesoscale rotational temperature variations and characteristics of internal gravity waves are maximum in spring and autumn. The spring maximum of mesoscale OH emission intensity variations is shifted to June. Interannual variations and multi-year trends of OH rotational temperature and emission intensity may differ in detail. This may be connected with seasonal and long-term variations in the complex system of the photochemical processes, which produce the OH nightglow.
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32

Hasan, Shaakeel, Peter A. Troch, J. Boll, and C. Kroner. "Modeling the Hydrological Effect on Local Gravity at Moxa, Germany." Journal of Hydrometeorology 7, no. 3 (June 1, 2006): 346–54. http://dx.doi.org/10.1175/jhm488.1.

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Abstract A superconducting gravimeter has observed with high accuracy (to within a few nm s−2) and high frequency (1 Hz) the temporal variations in the earth’s gravity field near Moxa, Germany, since 1999. Hourly gravity residuals are obtained by time averaging and correcting for earth tides, polar motion, barometric pressure variations, and instrumental drift. These gravity residuals are significantly affected by hydrological processes (interception, infiltration, surface runoff, and subsurface redistribution) in the vicinity of the observatory. In this study time series analysis and distributed hydrological modeling techniques are applied to understand the effect of these hydrological processes on observed gravity residuals. It is shown that the short-term response of gravity residuals to medium- to high-rainfall events can be efficiently modeled by means of a linear transfer function. This transfer function exhibits an oscillatory behavior that indicates fast redistribution of stored water in the upper layers (interception store, root zone) of the catchment surrounding the instrument. The relation between groundwater storage and gravity residuals is less clear and varies according to the season. High positive correlation between groundwater and gravity exists during winter months when the freezing of the upper soil layers immobilizes water stored in the unsaturated zone of the catchment. To further explore the spatiotemporal dynamics of the relevant hydrological processes and their relation to observed gravity residuals, a GIS-based distributed hydrological model is applied for the Silberleite catchment. Driven by observed atmospheric forcings (precipitation and potential evapotranspiration), the model allows the authors to compute the variation of water storage in three different layers: the interception store, the snow cover store, and the soil moisture store. These water storage dynamics are then converted to predicted gravity variation at the location of the superconducting gravimeter and compared to observed gravity residuals. During most of the investigated period (January 2000 to January 2004) predictions are in good agreement with the observed patterns of gravity dynamics. However, during some winter months the distributed hydrological model fails to explain the observations, which supports the authors’ conclusion that groundwater variability dominates the hydrological gravity signal in the winter. More hydrogeological research is needed to include groundwater dynamics in the hydrological model.
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33

Alexander, M. Joan, David A. Ortland, Alison W. Grimsdell, and Ji-Eun Kim. "Sensitivity of Gravity Wave Fluxes to Interannual Variations in Tropical Convection and Zonal Wind." Journal of the Atmospheric Sciences 74, no. 9 (August 15, 2017): 2701–16. http://dx.doi.org/10.1175/jas-d-17-0044.1.

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Abstract Using an idealized model framework with high-frequency tropical latent heating variability derived from global satellite observations of precipitation and clouds, the authors examine the properties and effects of gravity waves in the lower stratosphere, contrasting conditions in an El Niño year and a La Niña year. The model generates a broad spectrum of tropical waves including planetary-scale waves through mesoscale gravity waves. The authors compare modeled monthly mean regional variations in wind and temperature with reanalyses and validate the modeled gravity waves using satellite- and balloon-based estimates of gravity wave momentum flux. Some interesting changes in the gravity spectrum of momentum flux are found in the model, which are discussed in terms of the interannual variations in clouds, precipitation, and large-scale winds. While regional variations in clouds, precipitation, and winds are dramatic, the mean gravity wave zonal momentum fluxes entering the stratosphere differ by only 11%. The modeled intermittency in gravity wave momentum flux is shown to be very realistic compared to observations, and the largest-amplitude waves are related to significant gravity wave drag forces in the lowermost stratosphere. This strong intermittency is generally absent or weak in climate models because of deficiencies in parameterizations of gravity wave intermittency. These results suggest a way forward to improve model representations of the lowermost stratospheric quasi-biennial oscillation winds and teleconnections.
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34

Liu, Dong, Jiancheng Li, Zhe Ni, Yufei Zhao, Qiuyue Zheng, and Bin Du. "Correlation of Gravity and Magnetic Field Changes Preceding Strong Earthquakes in Yunnan Province." Applied Sciences 12, no. 5 (March 4, 2022): 2658. http://dx.doi.org/10.3390/app12052658.

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The annual variation trend of the gravity and lithospheric magnetic field for adjacent periods are analyzed by using the observation of rover gravity and geomagnetic fields in Yunnan from 2011 to 2021, which tend to be consistent every year during the seismogenic process of a strong earthquake. Thus, this study normalizes the annual value of the adjacent periods for the gravity and lithospheric magnetic field. The normalized values are converted into two classifications that can be compared within [−1,1]. In Yunnan Province, a grid of 0.1° × 0.1° was used to compare the data correlation between the variation of gravity and the variation in the lithospheric magnetic field at the same location. The results are as follows. First, the variation trend of the gravity field and total magnetic field tend to be synchronous year to year in strong earthquake years. The range of consistency increases gradually with the approach of the earthquake year reaching its maximum one year before the earthquake. Throughout the region, the overlap number of normalized annual variations in gravity and magnetic field reaches its maximum, and the peak difference of kernel density curve reaches its minimum. Second, the correlation coefficient of the annual variation in the gravity and magnetic field increases year to year during the development of a strong earthquake within a smaller region surrounding the event. The maximum appears one year before the earthquake, and after the earthquake, the correlation decreases. The analysis of gravity and magnetic fusion characteristics can be employed for the prediction of strong earthquakes.
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35

Wang, Lei, James L. Davis, Emma M. Hill, and Mark E. Tamisiea. "Stochastic filtering for determining gravity variations for decade-long time series of GRACE gravity." Journal of Geophysical Research: Solid Earth 121, no. 4 (April 2016): 2915–31. http://dx.doi.org/10.1002/2015jb012650.

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36

Timofeev, Vladimir Yu, Dmitriy G. Ardyukov, Anton V. Timofeev, Pavel Yu Gornov, Yurii F. Stus, and Vladimir M. Semibalamut. "VOLUME DEFORMATION VARIATIONS AND WELL-AQUIFER RESPONSE, ITS CONNECTION WITH GRAVITY MEASUREMENTS." Vestnik SSUGT (Siberian State University of Geosystems and Technologies) 26, no. 5 (2021): 40–51. http://dx.doi.org/10.33764/2411-1759-2021-26-5-40-51.

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Precise gravity measurements at g0·10 -9 level requires taking into account density change, caused by the Earth’s crust deformation and the movement and position of the fluid in the layer. The paper presents analysis of water level observation in three boreholes situated at Primorie, at Kamchatka and at Baikal region. Water-level fluctuations were influenced by earth tides, barometric pressure, co-seismic effects and season precipitations. Water tidal signal was analyzed for calculations of level-strain coefficients, its values changed from 0.1 mm/10-9 to 1.6 mm/10-9. Gravity corrections were developed by volume variation. For borehole drilled at monolithic rock we used the phaselag effect for tidal strain and crack-system orientation was studied in Pribaikalie mountain valley. Longterm gravity results were tested with water level data at Talaya station (Pribaikalie). Talaya gravity point situated at monolithic rock had no influence from water level variation. Level-correction was less than absolute gravity measurement error. Quick coseismic effects of earthquakes are well registered by level measuring, deformation graphical and absolute gravimetric methods.
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37

Antonov, Yu V. "The influence of the atmospheric front on the readings of the gravimeters and seismographs." Proceedings of higher educational establishments. Geology and Exploration, no. 4 (August 28, 2017): 66–71. http://dx.doi.org/10.32454/0016-7762-2017-4-66-71.

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Non-tidal variations of gravity are the residual part of the monitoring of the variations after subtraction from them the lunar-solar gravity variations and the drift of the zero point of the gravimeter. Non-tidal variations have a complex morphology and structure. The sources of the non-tidal variations are the intracrustal processes, flows of the charged particles in space and meteor showers. Meteor showers interacting with the Earth’s atmosphere determine the occurrence, development and movement in the atmosphere of the large-scale eddies - cyclones and anticyclones. The atmospheric fronts are distinguished in isolated cyclones. These fronts can influence the measurements of the gravimeters and seismographs.
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38

Ellewsen, Thor A. S., Bridget Falck, and David F. Mota. "Degeneracies between modified gravity and baryonic physics." Astronomy & Astrophysics 615 (July 2018): A134. http://dx.doi.org/10.1051/0004-6361/201731938.

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In order to determine the observable signatures of modified gravity theories, it is important to consider the effect of baryonic physics. We used a modified version of the ISIS code to run cosmological hydrodynamic simulations in order to study degeneracies between modified gravity and radiative hydrodynamic processes. One of the simulations was the standard Λ cold dark matter model and four were variations of the Symmetron model. For each model we ran three variations of baryonic processes: nonradiative hydrodynamics; cooling and star formation; and cooling, star formation, and supernova feedback. We constructed stacked gas density, temperature, and dark matter density profiles of the halos in the simulations, and studied the differences between them. We find that both radiative variations of the models show degeneracies between their processes and at least two of the three parameters defining the Symmetron model.
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39

Fritts, D. C., and S. L. Vadas. "Gravity wave penetration into the thermosphere: sensitivity to solar cycle variations and mean winds." Annales Geophysicae 26, no. 12 (December 2, 2008): 3841–61. http://dx.doi.org/10.5194/angeo-26-3841-2008.

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Abstract. We previously considered various aspects of gravity wave penetration and effects at mesospheric and thermospheric altitudes, including propagation, viscous effects on wave structure, characteristics, and damping, local body forcing, responses to solar cycle temperature variations, and filtering by mean winds. Several of these efforts focused on gravity waves arising from deep convection or in situ body forcing accompanying wave dissipation. Here we generalize these results to a broad range of gravity wave phase speeds, spatial scales, and intrinsic frequencies in order to address all of the major gravity wave sources in the lower atmosphere potentially impacting the thermosphere. We show how penetration altitudes depend on gravity wave phase speed, horizontal and vertical wavelengths, and observed frequencies for a range of thermospheric temperatures spanning realistic solar conditions and winds spanning reasonable mean and tidal amplitudes. Our results emphasize that independent of gravity wave source, thermospheric temperature, and filtering conditions, those gravity waves that penetrate to the highest altitudes have increasing vertical wavelengths and decreasing intrinsic frequencies with increasing altitude. The spatial scales at the highest altitudes at which gravity wave perturbations are observed are inevitably horizontal wavelengths of ~150 to 1000 km and vertical wavelengths of ~150 to 500 km or more, with the larger horizontal scales only becoming important for the stronger Doppler-shifting conditions. Observed and intrinsic periods are typically ~10 to 60 min and ~10 to 30 min, respectively, with the intrinsic periods shorter at the highest altitudes because of preferential penetration of GWs that are up-shifted in frequency by thermospheric winds.
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40

Kim, Jeong Woo, Ralph R. B. von Frese, and Hyung Rae Kim. "Crustal modeling from spectrally correlated free‐air and terrain gravity data—A case study of Ohio." GEOPHYSICS 65, no. 4 (July 2000): 1057–69. http://dx.doi.org/10.1190/1.1444799.

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We investigate the use of spectral correlation theory to analyze terrain gravity effects and free‐air gravity anomalies of Ohio for possible constraints on the thickness variations and neotectonics of the crust. Terrain gravity effects are computed from the topography by Gauss‐Legendre quadrature integration and are compared against independent free‐air gravity anomaly observations for their wavenumber correlation spectrum. Spectral correlation filters are designed accordingly to extract terrain‐correlated free‐air gravity anomalies that are subtracted from the terrain gravity effects for estimates of the compensated terrain gravity effects. These effects are used to model the Moho by inversion, assuming they predominantly reflect crustal thickness variations. Our results characterize the middle third of Ohio as a broad zone of thickened Precambrian crust, which also may include rifted regions where the thickness of the prerift crust has been reduced greatly. Furthermore, we find that about 83% of the instrumentally determined earthquake epicenters are located within the inferred thinner regions of Ohio’s crust or at their margins where compressional stresses may dominate. In general, these crustal thickness variations provide new constraints on modeling the tectonic evolution and geotechnical parameters of the crust—constraints that are important for evaluating earthquake hazards, the distribution and extraction of crustal resources, and the storage of hazardous waste and other crustal engineering applications.
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41

AL-Khafaji, Wadhah Mahmood Shakir. "Analyzing Gravity and Magnetic Data for the Detection of Deep-Seated Faults and Faults within the Sedimentary Cover Near Habbanieyah and Razzaza Lakes in the Middle of Iraq." Iraqi Geological Journal 54, no. 2C (September 30, 2021): 29–38. http://dx.doi.org/10.46717/igj.54.2c.3ms-2021-09-22.

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This research deals with the processing and analyzing of magnetic and gravitational data for an area covering the region of Habbanieyah - Razzaza Lakes and its adjacent areas. The study includes data processing and mapping of the total gravity and magnetic anomalies for only the concerned region, then separating the residual anomalies by adopting the polynomial regression graphical method. The residual gravity anomaly reflects the variations of rock densities within the sedimentary cover. The horizontal gradient filter has been applied to the residual gravity anomaly in order to conduct the locations of fault planes within the sedimentary cover where sudden variations of gravity field take place. The quantitative interpretation for both gravity and magnetic anomalies yielded a preliminary determination for the depth to the center of major faults within the sedimentary cover. By constructing a gravity model along a profile which directed NE-SW and passing through the middle part of the study region, depth to the center of the effective faults found. This depth variation is due to the effect of tectonic activity which produced a set of faults, such faults caused the upward and downward structural motions and were responsible for positioning the deep high density causative slabs of bedrock. The residual magnetic field quantitative interpretation along two profiles crosses over anomalies at the NE and SW parts of the region yielded the depth to the top of magnetized basement rocks. The difference in depth of the basement rocks and the shifted anomaly locations reflects the effect of tectonic activity which may relate to a strike slip faulting in the higher depths.
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42

Wang, Ling, Marvin A. Geller, and M. Joan Alexander. "Spatial and Temporal Variations of Gravity Wave Parameters. Part I: Intrinsic Frequency, Wavelength, and Vertical Propagation Direction." Journal of the Atmospheric Sciences 62, no. 1 (January 1, 2005): 125–42. http://dx.doi.org/10.1175/jas-3364.1.

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Abstract Five years (1998–2002) of U.S. high vertical resolution radiosonde data are analyzed to derive important gravity wave parameters, such as intrinsic frequencies, vertical and horizontal wavelengths, and vertical propagation directions in the lower stratosphere and troposphere. Intrinsic frequencies ω̂ increase with increasing latitude, with larger values in the troposphere. In the lower stratosphere, ω̂ is higher in winter than in summer, especially at mid- and high latitudes. Intrinsic frequencies divided by the Coriolis parameter f are ∼4 in the troposphere, and ∼2.4–3 in the lower stratosphere. The lower-stratospheric ω̂/f generally decreases weakly with increasing latitude. The latitudinal distributions of the lower-stratospheric ω̂/f are explained largely by the propagation effects. The seasonal variations of ω̂ in the lower stratosphere are found to be related to the variations of the background wind speeds. Dominant vertical wavelengths decrease with increasing latitude in the lower stratosphere, and maximize at midlatitudes (35°–40°N) in the troposphere. They are generally longer in winter than in summer. The variations of the dominant vertical wavelengths are found to be associated with the similar variations in gravity wave energies. Dominant horizontal wavelengths decrease with increasing latitude, with larger values in the lower stratosphere. Approximately 50% of the tropospheric gravity waves show upward energy propagation, whereas there is about 75% upward energy propagation in the lower stratosphere. The lower-stratospheric fraction of upward energy propagation is generally smaller in winter than in summer, especially at mid- and high latitudes. The seasonal variation of upward fraction is likely an artifice due to the analysis method, although a small part of it may be interpreted by the variations in background wind speeds. Results suggest that propagation effects are much more important than source variations for explaining the large-scale time-average properties of waves observed by radiosondes.
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43

Sato, Tadahiro, Yoichi Fukuda, Yuichi Aoyama, Herbert McQueen, Kazuo Shibuya, Yoshiaki Tamura, Kazuyoshi Asari, and Masatsugu Ooe. "On the observed annual gravity variation and the effect of sea surface height variations." Physics of the Earth and Planetary Interiors 123, no. 1 (March 2001): 45–63. http://dx.doi.org/10.1016/s0031-9201(00)00216-8.

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44

Ferreras, Ignacio, Francesco La Barbera, and Alexandre Vazdekis. "IMF variations in unresolved stellar populations: Challenges." Proceedings of the International Astronomical Union 11, A29B (August 2015): 193–94. http://dx.doi.org/10.1017/s1743921316004853.

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AbstractThis talk focuses on the challenges facing the recent discovery of variations of the stellar initial mass function in massive early-type galaxies, with special emphasis on the constraints via gravity-sensitive spectral features.
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45

Phelps, Geoff. "Forward modeling of gravity data using geostatistically generated subsurface density variations." GEOPHYSICS 81, no. 5 (September 2016): G81—G94. http://dx.doi.org/10.1190/geo2015-0663.1.

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Using geostatistical models of density variations in the subsurface, constrained by geologic data, forward models of gravity anomalies can be generated by discretizing the subsurface and calculating the cumulative effect of each cell (pixel). The results of such stochastically generated forward gravity anomalies can be compared with the observed gravity anomalies to find density models that match the observed data. These models have an advantage over forward gravity anomalies generated using polygonal bodies of homogeneous density because generating numerous realizations explores a larger region of the solution space. The stochastic modeling can be thought of as dividing the forward model into two components: that due to the shape of each geologic unit and that due to the heterogeneous distribution of density within each geologic unit. The modeling demonstrates that the internally heterogeneous distribution of density within each geologic unit can contribute significantly to the resulting calculated forward gravity anomaly. Furthermore, the stochastic models match observed statistical properties of geologic units, the solution space is more broadly explored by producing a suite of successful models, and the likelihood of a particular conceptual geologic model can be compared. The Vaca Fault near Travis Air Force Base, California, can be successfully modeled as a normal or strike-slip fault, with the normal fault model being slightly more probable. It can also be modeled as a reverse fault, although this structural geologic configuration is highly unlikely given the realizations we explored.
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46

Wang, Shuguang, Fuqing Zhang, and Chris Snyder. "Generation and Propagation of Inertia–Gravity Waves from Vortex Dipoles and Jets." Journal of the Atmospheric Sciences 66, no. 5 (May 1, 2009): 1294–314. http://dx.doi.org/10.1175/2008jas2830.1.

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Abstract This study investigates gravity wave generation and propagation from jets within idealized vortex dipoles using a nonhydrostatic mesoscale model. Two types of initially balanced and localized jets induced by vortex dipoles are examined here. These jets have their maximum strength either at the surface or in the middle levels of a uniformly stratified atmosphere. Within these dipoles, inertia–gravity waves with intrinsic frequencies 1–2 times the Coriolis parameter are simulated in the jet exit region. These gravity waves are nearly phase locked with the jets as shown in previous studies, suggesting spontaneous emission of the waves by the localized jets. A ray tracing technique is further employed to investigate the propagation effects of gravity waves. The ray tracing analysis reveals strong variation of wave characteristics along ray paths due to variations (particularly horizontal variations) in the propagating environment. The dependence of wave amplitude on the jet strength (and thus on the Rossby number of the flow) is examined through experiments in which the two vortices are initially separated by a large distance but subsequently approach each other and form a vortex dipole with an associated amplifying localized jet. The amplitude of the stationary gravity waves in the simulations with 90-km grid spacing increases as the square of the Rossby number (Ro), when Ro falls in a small range of 0.05–0.15, but does so significantly more rapidly when a smaller grid spacing is used.
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47

Alonso-Ojembarrena, A., and F. Raimondi. "The meaning of gravity-induced lung ultrasound score variations." Journal of Perinatology 42, no. 2 (November 29, 2021): 289. http://dx.doi.org/10.1038/s41372-021-01280-7.

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48

Bronnikov, K. A., and M. V. Skvortsova. "Variations of α and G from nonlinear multidimensional gravity." Gravitation and Cosmology 19, no. 2 (April 2013): 114–23. http://dx.doi.org/10.1134/s0202289313020035.

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49

Brasseur, Guy. "Atmospheric chemistry: Mesospheric ozone variations caused by gravity waves." Nature 313, no. 6000 (January 1985): 270. http://dx.doi.org/10.1038/313270a0.

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50

Weise, A., C. Kroner, M. Abe, J. Ihde, G. Jentzsch, M. Naujoks, H. Wilmes, and H. Wziontek. "Gravity field variations from superconducting gravimeters for GRACE validation." Journal of Geodynamics 48, no. 3-5 (December 2009): 325–30. http://dx.doi.org/10.1016/j.jog.2009.09.034.

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