Umberto Fracassi

Le contexte tectonique le long de la côte chilienne entre 36° et 38° S est marqué par un système de failles N-S qui contrôle le graben d'Arauco. Les linéations et les failles sont orientées NE-SW et déplacent le bord ouest du graben. L'expression du vent dominant, dirigé du SW vers le NE, se voit dans les formes d'érosion et dans la géométrie du réseau de drainage. (Résumé d'auteur)

The backbone of the Southern Apennines is perhaps the largest seismic moment release area in Italy. The region is dominated by an extensional regime dating back to the Middle Pleistocene, with maximum extension striking SW-NE (i.e. orthogonal to the mountain belt). The full length (~ 200 km) of the mountain range has been the locus of several destructive earthquakes occurring

Abstract For decades, alluvial plains have been the areas of the fastest population growth over most of the globe. Modern societies demand growing extensions of flat and easily accessible land to accommodate the swelling urban areas, booming industrial districts, ...

Recent seismicity in and around the Gargano Promontory, an uplifted portion of the Southern Adriatic Foreland domain, indicates active E–W strike-slip faulting in a region that has also been struck by large historical earthquakes, particularly along the Mattinata Fault. ...

ABSTRACT In December 1456-January 1457 a major earthquake sequence took place across the central and southern Apennines (southern Italy, Calabrian Arc excluded), including southeastern Apulia. A recent re-evaluation of the (a) revised damage pattern for this multiple earthquake, (b) deeper seismicity of the southern Apennines – Adriatic foreland interface and (c) deep-seated regional E-W structures, led to the identification of at least four seismogenic sources, responsible for the main sub-events of the multiple 1456 earthquake. Based on various seismological, macroseismic and tectonic constraints, these causative faults are thought to exhibit an oblique right-lateral motion along fault segments roughly E-W oriented. Such segments are portions of well-known inherited regional E-W trending shear zones (like the Molise-Gondola shear zone), at various latitudes between (from north to south) the Maiella Mts. and the Vulture volcanic complex. This system would therefore imply the cascade reactivation of such shear zones favorably oriented with respect to present stress field, with a transtensional mechanism. More than one catastrophic historical earthquake that occurred in southern Italy suggests the nearly simultaneous activation of multiple sources across widely spaced (+/- 30 km) portions of independent E-W faults. Being the strongest (by magnitude and damage area) among these major earthquakes, the 1456 sequence can be considered as a template for such mechanism of multiple activation of distant sources yet within a short time window. This hypothesis invokes a possible stress interaction between multiple sources falling within neighboring domains. We investigated Coulomb stress changes related to the main sub-events of the multiple 1456 earthquake to analyze fault interaction and stress transfer mechanisms. An evident positive correlation between the calculated Coulomb stress increase and two major seismogenic sources is found. Therefore, the spatial redistribution and enhancement of static stress caused by the stronger events may promote rupture on adjacent faults that are close to the failure threshold. A more general case may be considered imposing a pre-existing stress field or assuming different values for the friction coefficient. To the extents of present knowledge and investigation, these E-W trending earthquake sources are active between ca. 10 and 20 km at depth in the sector of the southern Apennines east of the chain axis, that is to say in the seismogenic macroregion bounded by the thrustbelt (to the west) and by the Apulian foreland (to the east). The stress patterns caused by these faults are consistent with the large NW-SE trending pure extensional sources found along the southern Apennines axis. Unpublished Vienna International Center Vienna Austria

Umberto Fracassi*, Pierfrancesco Burrato*, Roberto Basili*, Roberto Bencini*, Daniela Di Bucci° and Gianluca Valensise* ... Messapica (data from: Carta Geologica d Italia, Scale 1:100,000; Ciaranfi et al., 1988; Funiciello et al., 1991; Tropeano et al., 1997; Mastronuzzi and Sansò ...