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Sources of Mw 5+ earthquakes in northeastern Italy and western Slovenia: updated view based on geological and seismological evidence

By BURRATO P, M.E POLI, VANNOLI P, ZANFERRARI A, BASILI R and GALADINI F

Abstract

We present an overview of the seismogenic sources of northeastern Italy and western Slovenia, included in the last version of the Database of Individual Seismogenic Sources (DISS 3.0.2) and a new definition of the geometry of the Montello Source that will be included in the next release of the database. The seismogenic sources included in DISS are active faults capable of generating MwN5.5 earthquakes. We describe the method and the data used for their identification and characterization, discuss some implications for the seismic hazard and underline controversial points and open issues. In the Veneto\u2013Friuli area (NE Italy), destructive earthquakes up to Mw 6.6 are generated by thrust faulting along N-dipping structures of the Eastern Southalpine Chain. Thrusting along the mountain front responds to about 2 mm/a of regional convergence, and it is associated with growing anticlines, tilted and uplifted Quaternary palaeolandsurfaces and forced drainage anomalies. In western Slovenia, dextral strike\u2013slip faulting along the NW\u2013SE trending structures of the Idrija Fault System dominates the seismic release. Activity and style of faulting are defined by recent earthquakes (e.g. the Ms 5.7, 1998 Bovec\u2013Krn Mt. and the Mw 5.2, 2004 Kobarid earthquakes), while the related recent morphotectonic imprint is still a debated matter. We reinterpreted a large set of tectonic data and developed a segmentation model for the outermost Eastern Southalpine Chain thrust front. We also proposed the association of the four major shocks of the 1976 Friuli earthquake sequence with individual segments of three major thrust fronts. Although several sub-parallel active strike\u2013slip strands exist in western Slovenia, we were able to positively identify only two segments of the Idrija Fault System. A comparison of the regional GPS velocity with long-term geological slip-rates of the seismogenic sources included in DISS shows that from a quarter to half of the deformation is absorbed along the external alignment of thrust faults in Veneto and western Friuli. The partitioning of the deformation in western Slovenia among the different strike\u2013slip strands could not be quantified

Topics: Eastern Southern Alps, W-Slovenia, Seismogenic sources, DISS
Publisher: 'Elsevier BV'
Year: 2008
DOI identifier: 10.1016/j.tecto.2007.07.009
OAI identifier: oai:air.uniud.it:11390/855370
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