13,467 research outputs found
Joint inversion of muon tomography and gravimetry - a resolving kernel approach
Both muon tomography and gravimetry are geophysical methods that provide
information on the density structure of the Earth's subsurface. Muon tomography
measures the natural flux of cosmic muons and its attenuation produced by the
screening effect of the rock mass to image. Gravimetry generally consists in
measurements of the vertical component of the local gravity field. Both methods
are linearly linked to density, but their spatial sensitivity is very
different. Muon tomography essentially works like medical X-ray scan and
integrates density information along elongated narrow conical volumes while
gravimetry measurements are linked to density by a 3-dimensional integral
encompassing the whole studied domain. We develop the mathematical expressions
of these integration formulas -- called acquisition kernels -- to express
resolving kernels that act as spatial filters relating the true unknown density
structure to the density distribution actually recoverable from the available
data. The resolving kernels provide a tool to quantitatively describe the
resolution of the density models and to evaluate the resolution improvement
expected by adding new data in the inversion. The resolving kernels derived in
the joined muon/gravimetry case indicate that gravity data are almost useless
to constrain the density structure in regions sampled by more than two muon
tomography acquisitions. Interestingly the resolution in deeper regions not
sampled by muon tomography is significantly improved by joining the two
techniques. Examples taken from field experiments performed on La Soufri\`ere
of Guadeloupe volcano are discussed.Comment: Submitted to Geoscientific Model Developmen
Altimetry, gravimetry, GPS and viscoelastic modeling data for the joint inversion for glacial isostatic adjustment in Antarctica (ESA STSE Project REGINA)
The poorly known correction for the ongoing deformation of the solid Earth caused by glacial isostatic adjustment (GIA) is a major uncertainty in determining the mass balance of the Antarctic ice sheet from measurements of satellite gravimetry and to a lesser extent satellite altimetry. In the past decade, much progress has been made in consistently modeling ice sheet and solid Earth interactions; however, forward-modeling solutions of GIA in Antarctica remain uncertain due to the sparsity of constraints on the ice sheet evolution, as well as the Earth's rheological properties. An alternative approach towards estimating GIA is the joint inversion of multiple satellite data – namely, satellite gravimetry, satellite altimetry and GPS, which reflect, with different sensitivities, trends in recent glacial changes and GIA. Crucial to the success of this approach is the accuracy of the space-geodetic data sets. Here, we present reprocessed rates of surface-ice elevation change (Envisat/Ice, Cloud,and land Elevation Satellite, ICESat; 2003–2009), gravity field change (Gravity Recovery and Climate Experiment, GRACE; 2003–2009) and bedrock uplift (GPS; 1995–2013). The data analysis is complemented by the forward modeling of viscoelastic response functions to disc load forcing, allowing us to relate GIA-induced surface displacements with gravity changes for different rheological parameters of the solid Earth. The data and modeling results presented here are available in the PANGAEA database (https://doi.org/10.1594/PANGAEA.875745). The data sets are the input streams for the joint inversion estimate of present-day ice-mass change and GIA, focusing on Antarctica. However, the methods, code and data provided in this paper can be used to solve other problems, such as volume balances of the Antarctic ice sheet, or can be applied to other geographical regions in the case of the viscoelastic response functions. This paper presents the first of two contributions summarizing the work carried out within a European Space Agency funded study: Regional glacial isostatic adjustment and CryoSat elevation rate corrections in Antarctica (REGINA)
Testing Lorentz symmetry with planetary orbital dynamics
Planetary ephemerides are a very powerful tool to constrain deviations from
the theory of General Relativity using orbital dynamics. The effective field
theory framework called the Standard-Model Extension (SME) has been developed
in order to systematically parametrize hypothetical violations of Lorentz
symmetry (in the Standard Model and in the gravitational sector). In this
communication, we use the latest determinations of the supplementary advances
of the perihelia and of the nodes obtained by planetary ephemerides analysis to
constrain SME coefficients from the pure gravity sector and also from
gravity-matter couplings. Our results do not show any deviation from GR and
they improve current constraints. Moreover, combinations with existing
constraints from Lunar Laser Ranging and from atom interferometry gravimetry
allow us to disentangle contributions from the pure gravity sector from the
gravity-matter couplings.Comment: 12 pages, 2 figures, version accepted for publication in Phys. Rev.
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