scholarly journals A free-geometry geodynamic modelling of surface gravity changes using Growth-dg software

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Antonio G. Camacho ◽  
Peter Vajda ◽  
Craig A. Miller ◽  
José Fernández
Keyword(s):  
Time Variation ◽  
Gravity Data ◽  
Software Tool ◽  
Surface Gravity ◽  
Small Cells ◽  
Signal Noise ◽  
New Findings ◽  
Initial Hypothesis ◽  
Source Geometry ◽  
Surface Gravity Data

AbstractGlobally there is abundant terrestrial surface gravity data used to study the time variation of gravity related to subsurface mass and density changes in different geological, geodynamical and geotechnical environments. We present here a tool for analysing existing and newly acquired, 4D gravity data, which creates new findings from its reuse. Our method calculates in an almost automatic way the possible sources of density change responsible for the observed gravity variations. The specifics of the new methodology are: use of a low number of observation points, relatively small source structures, low signal/noise ratio in the data, and a free 3D source geometry without initial hypothesis. The process is based on the non-linear adjustment of structures defined by aggregation of small cells corresponding to a 3D section of the sub-floor volume. This methodology is implemented in a software tool, named GROWTH-dg, which can be freely downloaded for immediate use, together with a user manual and application examples.

Using isostatic gravity anomalies from spherical harmonic models and elastic plate compensation to interpret the lithosphere of the Bolivian Andes

Geophysics ◽  
2013 ◽  
Vol 78 (3) ◽  
pp. G41-G53 ◽  
Author(s):  
Christopher Jekeli ◽  
Hyo Jin Yang ◽  
Kevin Ahlgren
Keyword(s):  
Spherical Harmonic ◽  
Flexural Rigidity ◽  
Gravity Data ◽  
Gravity Anomalies ◽  
Surface Gravity ◽  
Bolivian Andes ◽  
Isostatic Gravity Anomalies ◽  
Isostatic Gravity ◽  
Spherical Harmonic Models ◽  
Surface Gravity Data

We have determined for the Bolivian Andes that the new global gravity models derived from the Gravity field and steady-state Ocean Circulation Explorer (GOCE) satellite mission may be used directly to study lithospheric structure. Toward this end, we have formulated Bouguer and isostatic gravity anomalies in spherical approximation, rather than in the usual planar approach, using spherical harmonic series consistent with the satellite-derived gravitational models. From the approximate equivalency of topographic masses and surface density layers using the Helmert condensation method we further derived and used isotropic transfer relations between the spherical spectra of topographic loads and elastic spherical shell deflections, where the Airy isostatic compensation is the special case of no flexural rigidity. A numerical comparison of these spherical harmonic models to conventional three-dimensional modeling based on topographic data and newly acquired surface gravity data in Bolivia confirmed their suitability for lithospheric interpretation. Specifically, the relatively high and uniform resolution of the satellite gravitational model (better than 83 km) produces detailed maps of the isostatic anomaly that clearly delineate the flexure of the Brazilian shield that is thrust under the Sub-Andes. Inferred values of the thickness of Airy-type roots and the flexural rigidity of the elastic lithosphere agree reasonably with published results based on seismic and surface gravity data. In addition, a local minimum in the flexural rigidity is evident at the sharp bend of the eastern margins of the Sub-Andes in Bolivia. This feature is consistent with earlier theories for counter rotations about a vertical axis at this minimum, associated with the confluence of the subducted Nazca plate and the Brazilian craton. The GOCE model thus generates high-resolution isostatic anomaly maps that offer additional structural detail not seen as clearly from previous seismic and gravity investigations in this region.

Some Problems Related to Geodetic Datum Definitions for Terrestrial Measurements

1975 ◽  
Vol 26 ◽  
pp. 247-259
Author(s):  
E. Groten
Keyword(s):  
Gravity Data ◽  
Surface Gravity ◽  
Earth Model ◽  
Reference Systems ◽  
Crustal Motion ◽  
Absolute Orientation ◽  
Orientation Vector ◽  
Definition Of ◽  
Surface Gravity Data

AbstractProblems related to the precj se definition of reference systems for measurements of crustal motion are discussed. Difficulties in defining vertical positions are emphasized. Using the Goddard Earth Model 6 and surface gravity data, a new absolute orientation vector for the European Datum is evaluated and corresponding deficiencies are discussed.

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