Comment on “The computation of aliasing effects in local gravity field approximation”

1988 ◽  
Vol 62 (4) ◽  
pp. 565-567
Author(s):  
C. Jekeli ◽  
R. Forsberg
Keyword(s):  
Gravity Field ◽  
Field Approximation ◽  
Local Gravity

The computation of aliasing effects in local gravity field approximation

1988 ◽  
Vol 62 (1) ◽  
pp. 41-58
Author(s):  
Anthony A. Vassiliou
Keyword(s):  
Gravity Field ◽  
Field Approximation ◽  
Local Gravity

scholarly journals Three years of high precision gravity measurements at the gravimetric station of Brasimone - Italy

1998 ◽  
Vol 41 (2) ◽  
Author(s):  
G. Casula
Keyword(s):  
Gravity Field ◽  
High Precision ◽  
Nuclear Power ◽  
Meteorological Data ◽  
Normal Modes ◽  
Superconducting Gravimeter ◽  
Mass System ◽  
Global Geodynamics ◽  
Local Gravity ◽  
Italian Apennines

From August 1995 up to now, at the Enea Research Center of Brasimone, in the Italian Apennines between Bologna and Florence (Italy: 44º07'N, 11º.07'E, 890 m height), the superconducting gravimeter GWR model TT70 number T015 has been continuously recording the variation of the local gravity field, in the frame of the Global Geodynamics Project. The gravimetric laboratory, being a room of the disused nuclear power plant of Brasimone, is a very stable site, free from noise due to human activities. Data blocks of several months of continuous gravity records have been collected over a time span of three years, together with the meteorological data. The gravimeter has been calibrated at relative accuracy better than 0.3% with the aid of a mobile mass system, by imposed perturbations of the local gravity field and recording the gravimeter response. The results of this calibration technique were checked by two comparison experiments with absolute gravimeters performed during this period: the first, in May 1994 with the aid of the symmetrical rise and fall gravimeter of the Institute of Metrology Colonnetti of Turin, and the second in October 1997 involving an FG5 absolute gravimeter of the Institute de Physique du Globe of Strasbourg. The gravimeter signal was analysed to compute a high precision tidal model for Brasimone site. Starting from a set of gravimetric and atmospheric pressure data of high quality, relative to 46 months of observation, we performed the tidal analysis using Eterna 3.2 software to compute amplitudes, gravimetric factors and phases of the main waves of the Tamura catalogue. Finally a comparison experiment between two of the STS-1/VBB broadband seismometers of the MedNet project network and the gravity records relative to the Balleny Islands earthquake (March 25, 1998) were analysed to look for evidence of normal modes due to the free oscillations of the Earth.

FVM approach for solving the oblique derivative BVP on unstructured meshes above the real Earth’s topography

2020 ◽  
Author(s):  
Matej Medľa ◽  
Karol Mikula ◽  
Róbert Čunderlík
Keyword(s):  
Boundary Condition ◽  
Gravity Field ◽  
Finite Volume ◽  
Normal Component ◽  
Gravity Field Modelling ◽  
The Real ◽  
Field Modelling ◽  
Advection Term ◽  
Local Gravity ◽  
Local Gravity Field Modelling

<p>We present local gravity field modelling based on a numerical solution of the oblique derivative bondary value problem (BVP). We have developed a finite volume method (FVM) for the Laplace equation with the Dirichlet and oblique derivative boundary condition, which is considered on a 3D unstructured mesh about the real Earth’s topography. The oblique derivative boundary condition prescribed on the Earth’s surface as a bottom boundary is split into its normal and tangential components. The normal component directly appears in the flux balance on control volumes touching the domain boundary, and tangential components are managed as an advection term on the boundary. The advection term is stabilised using a vanishing boundary diffusion term. The convergence rate, analysis and theoretical rates of the method are presented in [1].</p><p>Using proposed method we present local gravity field modelling in the area of Slovakia using terrestrial gravimetric measurements. On the upper boundary, the FVM solution is fixed to the disturbing potential generated from the GO_CONS_GCF_2_DIR_R5 model while exploiting information from the GRACE and GOCE satellite missions. Precision of the obtained local quasigeoid model is tested by the GNSS/levelling test.</p><p> </p><p>[1] Droniou J, Medľa M, Mikula K, Design and analysis of finite volume methods for elliptic equations with oblique derivatives; application to Earth gravity field modelling. Journal of Computational Physics, s. 2019</p>

Expected impact of the 2016 central Italy earthquakes on the local gravity field

2020 ◽  
Author(s):  
Federica Riguzzi ◽  
Hongbo Tan ◽  
Chong-yang Shen
Keyword(s):  
Gravity Field ◽  
Half Space ◽  
Near Field ◽  
Source Parameters ◽  
Central Italy ◽  
Far Field ◽  
Dislocation Theory ◽  
Local Gravity ◽  
Vertical Displacements ◽  
Gnss Observations

<p>We have modelled the surface volume and gravity changes caused by the three mainshocks (moment magnitudes Mw 6.0, 5.9, 6.5) occurred during the last seismic period started on 2016, August 24 in central Italy. Our calculations start from the source parameters estimated by the inversion of the largest dataset of InSAR and GNSS observations ever managed in Italy after earthquake occurrences, based on the half-space elastic dislocation theory. The vertical displacements modelled after the 2016 events allow to infer a substantial unbalance between the subsided and uplifted volumes. In particular, we detected ~106∙10<sup>6</sup> m<sup>3</sup> of hangingwall subsidence against ~37∙10<sup>6</sup> m<sup>3</sup> of footwall uplift, that accounts for ~74% of the total volume mobilization. From the ratio between the footwall and total deformed volumes, we have computed an average fault dip of ~47°, in line with the values retrieved by seismological methods. The total gravity variations which affected the study area are of the order of ~1 μGal (1 μGal = 10<sup>−8</sup> ms<sup>−2</sup>) in the far field, and ~170 μGal in the near field.<br>The area affected within a gravity change of 1 μGal is ~140 km long and ~57 km wide, parallel to the Apennines chain. The larger contribution is given by positive variations which account for the tensional style of deformation and larger subsided area.</p>

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