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Optimal, scalable forward models for computing gravity anomalies

May, Dave A. ; Knepley, Matthew G.

In: Geophysical Journal International, 2011, vol. 187, no. 1, p. 161-177

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    Title
    • Optimal, scalable forward models for computing gravity anomalies
    Author
    • May, Dave A.. Institute of Geophysics, Department of Earth Sciences, ETH Zürich, Zürich, Switzerland.
    • Knepley, Matthew G.. Computation Institute, University of Chicago, Illinois, USA
    Document Type
    • Postprint
    OAI-PMH Identifier
    • oai:doc.rero.ch:289214
    Summary
    We describe three approaches for computing a gravity signal from a density anomaly. The first approach consists of the classical ‘summation' technique, while the remaining two methods solve the Poisson problem for the gravitational potential using either a finite-element (FE) discretization employing a multilevel pre-conditioner, or a Green′s function evaluated with the fast multipole method (FMM). The methods using the Poisson formulation described here differ from previously published approaches used in gravity modelling in that they are optimal, implying that both the memory and computational time required scale linearly with respect to the number of unknowns in the potential field. Additionally, all of the implementations presented here are developed such that the computations can be performed in a massively parallel, distributed memory-computing environment. Through numerical experiments, we compare the methods on the basis of their discretization error, CPU time and parallel scalability. We demonstrate the parallel scalability of all these techniques by running forward models with up to 108 voxels on 1000s of cores