“…Geophys. Geod., 51 (2007) 2004), the boundary element method (BEM) (Rodríguez-Castellanos et al, 2005;Pointer et al, 1998;Liu and Zhang, 2001;Iturrarán-Viveros et al, 2005), or the finite difference methods (FDM) (e.g. Frankel and Clayton, 1986;Roth and Korn, 1993;van Baren et al, 2001;Saenger and Shapiro, 2002;Krüger et al, 2005).…”