MAPPING CRUSTAL STRAIN AND STRESS FIELDS ACROSS THE DEAD SEA FAULT SYSTEM BY GPS OBSERVATIONS AND FOCAL PLANE SOLUTIONS P. Imprescia 1,2 , M. Palano 3 and S. Gresta 1 1 Dipartimento di Scienze Biologiche, Geologiche e Ambientali – Università degli Studi di Catania, Italy 2 Istituto di Geologia Ambientale e Geoingegneria – Consiglio Nazionale delle Ricerche, Rome, Italy 3 Istituto Nazionale di Geofisica e Vulcanologia – Osservatorio Etneo, Sezione di Catania, Italy Introduction. The Dead Sea Fault System (DSFS) represents the left-lateral transform boundary between the Arabian and Sinai plates (e.g. Jackson and McKenzie, 1988), stretching from the Red Sea mid-oceanic ridge to the south, to the Bitlis-Zagros (southern Turkey) continental collision zone to the north, where the DSFS joins with the East Anatolian fault (EAF; Fig. 1a). The DSFS is generally subdivided into three sections (Fig. 1b). The southern section, extending from the Gulf of Aqaba (Red Sea) through the Jordan Valley, is characterized by the presence of predominantly left- lateral strike-slip faults striking between N12°E and N20°E, having a small component of extension in the south (Gulf of Aqaba) and increasing compression toward the north (Bartov et al., 1980; Garfunkel, 1981; Galli, 1999; Gomez et al., 2003). The central section is a ca. 200 km long NNE- SSW striking restraining bend through Lebanon and SW Syria where the DSFS joins with the Palmyride Fold belt (PFB). Within the restraining bend, the DSFS comprises several distinct fault branches which trend roughly parallel to the strike of PFB (Garfunkel, 1981; Walley, 1988; Girdler, 1990). The ca. 120-km-wide PFB consists of many asymmetrical elongated anticlines separated by narrow depressions extending in central Syria (Chaimov et al., 1990). Northward, the DSFS splays into two distinct N-S striking faults bounding the 70-km-long Ghab Valley and extending to the Bitlis-Zagros collision zone between Arabia and Anatolia (Gomez et al., 2003). A total left-lateral slip of 105 km, occurred into two main phases, has been documented along the southern segment of DSFS. About 60 km of displacement were accrued before the Miocene, while about 45 km were accrued from Miocene to present (Quennell, 1958; Freund et al., 1970; Weber et al., 2009). Conversely, the northern segment of the DSFS, apparently shows considerably less displacement (5.3-16.8 km in the last 3.7 Ma; Searle et al., 2010) with respect to the southern segment (Walley, 1988). The discrepancy between the displacement along the northern and southern sector of the DSFS is puzzling, since the PFB accounts only 20 km by folding shortening (Chaimov et al., 1990). The occurrence of several large earthquakes (with magnitude ≥ 7) in the last 2000 years along the DSFS, is well documented in the historical records (Fig. 1b; Ambraseys and Jackson, 1998; Klinger et al., 2000; Sbeinati et al., 2005). However, the historical earthquakes are unequally distributed along the DSFS, with the occurrence of more than 8 large earthquakes in its northern sector (in the area comprises between the Ghab Valley and the Kara Su Valley; Fig. 1b) and only four events in its southern sector (AD 1068, AD 1212, AD 1293 and AD 1458; Klinger et al., 2000). Since the beginning of instrumental seismicity the DSFS experienced only one larger earthquake that struck the Gulf of Aqaba on November 22, 1995 (yellow star in Fig. 1b; Klinger et al., 2000). Here, we focused on the present-day crustal tectonic stress and the strain-rate fields occurring along the entire DSFS by analyzing seismological data (i.e. fault plane solutions collected from public catalogues and literature data) and geodetic data (GPS-based velocity field coming from recently continuously operating stations which were rigorously integrated with published velocities) in order to provide a more complete picture of the ongoing state of stress and crustal deformation occurring along the DSFS. Seismic data. Recent instrumental crustal seismicity (M ≥ 2.5) occurred on the investigated area since 1980 (http://www.isc.ac.uk) is not uniformly distributed along the entire DSFS, but results concentrate into three main regions (Fig. 1c). The northernmost region, including the northern sector of DSFS and the southern part of EAF, is characterized by a widespread seismicity (with the occurrence of 12 events with M ≥ 5.0) which well depicts the complex nature of the DSFS-EAF tectonic interaction. The central section of DSFS, where it joins with the PFB, is also characterized by a widespread seismicity (with the occurrence of 2 events with M ≥ 5.0), while on the eastern part 64 GNGTS 2012 SESSIONE 1.1