GNGTS 2017 - 36° Convegno Nazionale

GNGTS 2017 S essione 1.2 177 To the SW, although the slab seismicity shows an incipient narrowing at about 70-100 km of depth, the boundary is sharper and emphasized by lateral velocity discontinuities and by earthquake lineaments. These features take place in a narrow sector, perpendicular to the slab hinge, extending between Vulcano and the Ionian Sea. There, the hypocentre distribution suggests an array of NE-dipping seismogenic structures, deep down to 70 km (Fig.1; section DD’). Moreover, other seismic, geological and geodetic evidences indicate right-transtensional tectonics.All these features could be framed within a large deformation zone delimiting laterally the Sicilian (continental) and the subducting Ionian (oceanic) lithospheres. References Calò M., Dorbath C., Luzio D., Rotolo S.G. and D’Anna G.; 2009: Local earthquake tomography in the Southern Tyrrhenian region of Italy: Geophysical and petrological inferences on the subducting lithosphere . in Subduction Zone, Geodynamics, vol. 3, edited by S. Lallemand and F. Funiciello, pp. 86–100, Springer, Berlin, doi: 10.1007/978-3-540-87974. Carminati E. and Doglioni C.; 2005: Mediterranean tectonics . �� ������������ �� �������� ��������� ������� In Encyclopedia of Geology, Elsevier, 135-146 Koulakov I.; 2009: LOTOS code for local earthquake tomographic inversion: Benchmarks for testing tomographic algorithms . Bull. Seismol. Soc. Am., 99(1), 194–214, doi:10.1785/0120080013. Zhang H., Thurber C. and Bedrosian P.; 2009: Joint inversion for Vp, Vs, and Vp/Vs at SAFOD, Park eld, California . Geochem. Geophys. Geosyst., 10, Q110032, doi:10.1029/2009GC002709. Is there any relationship between the dewatering of the Fucino lake (1875) and the occurrence of the M7 Fucino earthquake (1915)? A. Tertulliani 1 , L. Cucci 1 , G. Currenti 2 , M. Palano 2 1 Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Sismologia e Tettonofisica, Rome, Italy 2 Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Etneo, Catania, Italy We explored the possibility of a relationship between the dewatering of the great lake that formerly occupied the Fucino intermountain basin (central Italy; Fig. 1) and the occurrence of seismicity recorded in the area since the 20 th century and culminated with a M=7 earthquake in 1915 (Cucci and Tertulliani, 2015). The Fucino lake occupied a depressed area of almost 150 km 2 with a rather constant depth of ~20 m; it was the largest lake of peninsular Italy. The area, agriculturally developed since Roman time, suffered severe floods during the rainy season due to the huge amount of water provided by karst aquifers in the surrounding mountains, the lack of natural effluents and the flatness of the surrounding shores. In order to mitigate the flood hazard a number of engineering projects aimed to the drainage of excess waters have been carried out (see Ward and Valensise, 1989 and references therein for additional details). The first dewatering project started in 52 A.D., with the excavation of a tunnel beneath the lake in order to drain excess waters into the deeper Liri Valley to the west. After a number of attempts to keep the water level within a limited portion of the depression, the lake was completely drained in 1875 following an ambitious engineering project lasted twenty years. By 1900, the old lake became the most important agricultural site of the region. Several small villages located around the lake shore rapidly developed, the most populous being Avezzano (Fig. 1). The Fucino basinwas struck by aM7 earthquake on 13 January 1915; such an event represents one of the most destructive seismic events ever occurred in Central Italy (see Rovida et al., 2016 for additional details). The basin is bordered to the east and southeast by some quaternary faults (the Parasano and Serrone faults; Fig. 1), which were reactivated by the 1915 event, with a recognized rupture of about 23 km in length (Amoruso et al. , 1988). This earthquake aroused