_______________________________ 1 University of L'Aquila, Italy. 2 Studio Prof. Marchetti, Roma, Italy. 37 Site characterization by seismic dilatometer (SDMT) in the area of L'Aquila Sara Amoroso 1 , Diego Marchetti 2 , Silvano Marchetti 2 , Paola Monaco 1 , Ferdinando Totani 1 , Gianfranco Totani 1 Abstract The seismic dilatometer (SDMT) is the combination of the standard flat dilatometer (DMT) with a seismic module for measuring the shear wave velocity V S . This paper presents the most significant results ob- tained by SDMT in the area of L'Aquila following the April 6, 2009 earthquake. 1. Introduction The seismic dilatometer (SDMT) is the combination of the tradi- tional "mechanical" flat dilatometer (DMT) introduced by Marchetti (1980) with a seismic module placed above the DMT blade. The SDMT module is a probe outfitted with two receivers, spaced 0.5 m, for measuring the shear wave velocity V S . From V S the small strain shear modulus G 0 may be determined using the theory of elasticity. The SDMT equipment, test procedure and interpretation are briefly described in the paper. Detailed information and comments on SDMT results and applications can be found in previous papers, in particular in Marchetti et al. (2008). Information on the mechanical DMT, not described in this paper, can be found in the comprehensive report by the ISSMGE Technical Committee TC16 (2001). This paper comments on the most significant results obtained by seismic dilatometer tests executed in the period 2009-2010 at several sites in the area of L'Aquila. Some of these tests were carried out in the first months following the April 6, 2009 earthquake, as part of site The dynamic interaction of soil and structure ISBN 978–88–548–3693–8 DOI 10.4399/97888548369383 pag. 37–62 (febbraio 2011)