“…Geophysical methods have already been demonstrated as useful tools for noninvasive EDZ/HDZ detection. A large amount of research has been conducted on the use of active and passive seismic methods for this purpose (see Carlson and Young, 1993;Cabrera et al, 1999;Backblom and Martin, 1999;Cosma et al, 2001;Alheid et al, 2002;Malmgren et al, 2007, for example). Ground Penetrating Radar (GPR) and resistivity methods have shown potential in a few isolated studies, although their use requires further testing and development (Scott et al, 1968;Kruschwitz and Yaramanci, 2004;Suzuki et al, 2004;Gibert et al, 2006;Silvast and Wiljanen, 2008;Kantia et al, 2013;Lesparre et al, 2013).…”