Elastic modeling of the Alto Tiberina normal fault (central Italy): geometry and lithological stratification influences on the local stress field Cristina Pauselli * , Costanzo Federico Dipartimento di Scienze della Terra, Universita ` degli Studi di Perugia, P.zza dell’Universita ` 1, 06100 Perugia, Italy Received 24 October 2002; accepted 11 June 2003 Abstract Two-dimensional, elastic, plane-strain, finite element models (FEMs) are generated to study the state of stress and failure induced by a low-angle normal fault, the Alto Tiberina Fault of the Northern Apennines (central Italy): it is beyond the scope of the present work to show that slip can occur on such a fault. The numerical study was performed to evaluate the influences on the local stress field of the litho-mechanical stratification of formations surrounding the fault, and those induced by the geometry of the fault. The performed models have shown the important role played by evaporites and basement formations of the Umbria-Marche succession as seismogenetic layers. The model results have also underlined that the flat-ramp geometry of the fault induces high relative concentration of stresses in correspondence with the low-angle, east-dipping, synthetic normal faults observed today in shallow depth near the Alto Tiberina surface trace. The stress regime predicted by the final model, in which the behavior of the Alto Tiberina together with the antithetic normal fault of Gubbio was simulated, reconciles available geological and geophysical observable to a greater extent. The numerical results can assist interpretation of the tectonic evolution of the region. D 2003 Elsevier B.V. All rights reserved. Keywords: Northern Apennines; Elastic modeling; Stress field; Seismicity 1. Introduction The Northern Apennines chain (NA), located in central Italy (Fig. 1), is a NE verging thrust and fold belt, involving rocks that become progressively shal- lower from the inner to the outer part. The available geological (e.g., Signorini, 1940; Migliorini, 1948; Selli, 1954), petrological (Peccerillo et al., 1987; Serri et al., 1993) and geophysical studies (e.g., Calcagnile and Panza, 1981; Alfano et al., 1982; Nicolich and Marson, 1994) with the recent results of the Deep Seismic Reflection profile, Crop03 (Pialli et al., 1998), have shown that the NA is characterized by two adjacent structural domains (Alfano et al., 1982; Barchi et al., 1998a): an internal (western) sector, the Tyrrhenian domain, and an external (eastern) sector, the Adriatic domain (Fig. 1). These two domains have different characteristics both from the geological and the geophysical point of view. The transition between the two domains takes place in a belt passing through the Perugia-Lago Trasimeno area (Umbria region) in a 0040-1951/$ - see front matter D 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0040-1951(03)00235-X * Corresponding author. Fax: +39-75-5852603. E-mail address: geof@unipg.it (C. Pauselli). www.elsevier.com/locate/tecto Tectonophysics 374 (2003) 99– 113