Inverse Model Approach for vertical Load Deformations in Consideration of Crustal Inhomogeneities
Mass redistributions in various components of the Earth system exert time-variable surface loads on the solid Earth. The resulting variations of the Earth’s geometry are reflected by vertical and horizontal displacements of geodetic markers. Usually the effect of loading on crustal deformation is computed by means of a weighting function which is based on site-independent load Love numbers (Green’s function). But as the Earth’s crust is composed of heterogeneous material, the adequateness of a site-independent approach deserves a review. We propose a procedure for the computation of vertical crustal deformations in which the Green’s function is substituted by a site-dependent exponential function. Its parameters are estimated by means of least-squares adjustment using time series of globally distributed GPS sites. On the basis of the crustal model Crust2.0 regions are predefined for which identical parameters are determined. Pressure fields of atmosphere, continentalhydrosphere and oceans are considered as forcing. In order to validate the numerical results, model time series from both the traditional and the site-dependent approach are compared with GPS observations. Explicit improvement is achieved in regions which are covered well with observations and feature strong pressure variability. However in regions like Africa and Antarctica parameter estimation is difficult due to the sparse distribution of GPS sites.
KeywordsInverse model vertical site displacements surfaceloading Green’sfunction GPS
Unable to display preview. Download preview PDF.
- Bassin C, Laske G, Masters G (2000): Thecurrentlimits of resolution for surface wave tomography in North America. EOS Trans AGU 81: F897Google Scholar
- Gross RS, Fukimori I, Menemenlis D (2003): Atmospheric and oceanic excitation of the Earth’s wobbles during 1980-2000. J Geophys Res 108: doi:10.1029/2002JB002143Google Scholar
- Lambeck K (1980): The Earth’s Variable Rotation: Geophysical Causes and Consequences. Cambridge University Press, New YorkGoogle Scholar
- Moritz H, Mueller II (1987): Earth Rotation: Theory and Observation. Ungar Publishing Company, New YorkGoogle Scholar
- Rabbel W, Zschau J (1985): Static deformations and gravity changes at the Earth’s surface due to atmospheric loading. J Geophysics 56: 81-99Google Scholar
- Schuh H, Estermann G, Crétaux JF, van Dam TM, Bergé-Nguyen M (2004): Investigation of hydrological and atmospheric loading by space geodetic techniques. In: Hwang C, Shum CK, Li JC (eds) Satellite Altimetry for Geodesy, Geophysics and Oceanography, IAG Symposia 126, Springer, Berlin, pp 123-132Google Scholar
- Scherneck HG (1990): LoadingGreen’sfunctionsfor a continental shield with a Q-structure for the mantle and density constraints from the geoid. Bulletin d’Information Marées Terrestres 108: 7757-7792Google Scholar
- Seitz F (2005): Atmospheric and oceanicin influences on polar motion -Numerical results from two independent model combinations. Artificial Satellites 40(3): 199-215Google Scholar