1. Univ. Lille, CNRS, INRAE, Centrale Lille , UMR 8207 - UMET, F-59000 Lille , France
2. Institute of Geophysics, University of Münster , Corrensstr. 24, 48149 Münster , Germany
3. Department of Geology and Geophysics, University of Utah , Salt Lake City, UT 84112 , USA
4. Laboratoire de Planétologie et Géodynamique, CNRS , UMR 6112, Université de Nantes, 44035 Nantes Cedex 1 , France