surface gravity data
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2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Antonio G. Camacho ◽  
Peter Vajda ◽  
Craig A. Miller ◽  
José Fernández

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.


2020 ◽  
Vol 20 (1) ◽  
pp. 59-66
Author(s):  
Susheel Dangol ◽  
Prakash Joshi ◽  
Suraj KC ◽  
Mahesh Thapa ◽  
Mahesh Thapa ◽  
...  

The height measurement of the highest peak of the world “Sagarmatha” was conducted by Nepal for the first time. The methodology for the measurement was finalized from the workshop held in Kathmandu with the constructive comments from national and international experts. Trignometrical levelling, precise levelling, GNSS survey and gravity survey was conducted. Previous air borne gravity data and present surface gravity data was used to determine the precise regional geoid for this program. Thus orthometric height was determined as 8848.86 m from the ellipsoid height observed at the top of Sagarmatha and precise geoid determined. The height was determined on the base of International Height Reference System (IHRS) and final height was announced jointly from Nepal and China on 8th of December 2020 from Kathmandu and Beijing through virtual media.


Geophysics ◽  
2013 ◽  
Vol 78 (3) ◽  
pp. G41-G53 ◽  
Author(s):  
Christopher Jekeli ◽  
Hyo Jin Yang ◽  
Kevin Ahlgren

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.


1998 ◽  
Vol 103 (B2) ◽  
pp. 2615-2631 ◽  
Author(s):  
Valérie Ballu ◽  
Jacques Dubois ◽  
Christine Deplus ◽  
Michel Diament ◽  
Sylvain Bonvalot

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