GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 2.1 GNGTS 2023 sediments. During the Tertiary, northern Central America experienced violent continental volcanism (Bommer and Rodriguez, 2002). Accordingly, El Salvador territory is constituted, at about 95%, of volcanic rocks and soils and alluvial deposits. From a geomorphological viewpoint, El Salvador is characterised by “sierras”, as the northern Central America arc (South part of Mexico, Guatemala, Honduras, northern Nicaragua, and the Caribbean coast). These “sierras” are formed of a number of sub-parallel ranges, composed of metamorphosed deposits, separated from each other by faults and grabens (Bommer and Rodriguez, 2002). They are largely affected by seismically-induced instability. Slope instability induced by the 13 January 2001 earthquake The strong earthquake of January 13, 2001 at 17:33:34 UTC (M w 7.7 - Depth 60 km, 20 km offshore) was the fifth destructive earthquake to affect El Salvador in the last fifty years and it was responsible for 1081 landslides all around the country. Among them, some affected severely two municipalities, i.e., Comasagua and San Salvador. In this latter, at Santa Tecla city area, a complex landslide (slide and flow mechanisms) with a volume of 150,000 m 3 destroyed numerous houses and caused 600 casualties. In Fig. 2, the study area (black square) and the outcropping lithotypes are reported. In this place, known as the Balsamo range, the calculated D values have been compared to the seismically-induced landslide inventory mapped by Mercurio et al. (2021) from the aerial images taken by the CNR (Centro Nacional de Registros - Instituto Geográfico y del Catastro Nacional) in the aftermath of the main shock of January 13, 2001.