SEISMOTECTONIC MAP OF THE NORTHERN SICILY CONTINENTAL MARGIN (NSCM) AND IMPLICATIONS FOR GEOHAZARD ASSESSMENT

Risultato della ricerca: Otherpeer review

Abstract

The Sicily dominates the central MediterraneanSea. The Northern Sicily Continental Margin(NSCM) is a segment of the Appeninic-TyrrhenianSystem whose upbuilding refers to both the postcollisionalconvergence between Africa and a verycomplex “European” crust (Bonardi et al., 2001) orAlKaPeKa (sensu Boullin, 1986) and the opening ofthe Tyrrhenian back-arc basin. Seismostratigraphicand structural analysis of a largenumber of available (from ViDePi project) andunpublished (from Department of Earth andMarine Science of the University of Palermo)multichannel seismic reflection profiles acquiredacross the NSCM, allow us to produce an accurateseismotectonic map, in order to obtain a usefultool for the assessment of the seismic hazard ofthe sea-land region. This first seismotectonic maphas been realised from the overlapping ofdifferent geological layers that represent the mainidentified seafloor and sub-seafloor features, suchas tectonic elements (normal and revers faults),earthquakes, heat flow, gravimetric (Bouguer) andmagnetometric anomalies, Moho depth, masswasting,fluid escape structures (e.g. pockmarks,mounds, gas flares, and gas chimneys),sedimentary successions, and lateral and verticalmotions. The NSCM is suitable to test thisapproach because it is located in a transitionalarea between the Sicilian-Maghrebian chain to thesouth and the Tyrrhenian back-arc basin to thenorth. Along this transect the Moho depth rangesfrom about 10 km, in the Marsili bathyal plain, toabout 40 km, towards the northern Sicily coast.The Bouguer anomalies change from 180 mGal inthe Tyrrhenian region to negative anomalies incentral Sicily (-100 mGal), while positive magneticanomalies characterize the volcanic edifices, bothsubmerged and buried. While, the heat flowshows very high values across the southernTyrrhenian Sea (200 mW/m-2) that decrease (30-40 mW/m-2) towards the stable sector of theforeland area (Iblean plateau in SE Sicily). Alongthe NSCM, we distinguished, at a regional scale,different shallow and deep seismogeneticvolumes. The eastern part of the Siciliancontinental margin is characterised by a deeperseismicity related to the Ionian subduction, whichis prevailingly linked both to extensional faultsystems (Pollina, Messina strait) and to rightlateralNW-SE transcurrent systems (Vulcano-Lipari and Tindari-Giardini). While the westernregion shows shallow earthquakes (up to 25 km)of low to moderate magnitude (max Mw 5.9 onSeptember 2002) occurring along an E-W trendingbelt and resulting from the brittle deformation ofthe Maghrebian chain. The focal mechanismsrelated to the main seismic shocks are inagreement with a dominant NW-SE compressiveoffset direction, with a right strike-slipcomponent, and an antithetic NE-SW fault trend.Evidences of mass-wasting processes have beenidentified across the continental shelf and thecontinental slope and their spatial distribution,geometry, and seismic character suggest that thefluid seepage, oceanographic processes and theslope oversteepening could be importantpreconditioning factors, while the tectonic activityshowing fault displacements during earthquakesis the main trigger. During the last 125 ky tectonicactivity is evidenced by an uplift/subsidencepatterns, decreasing from E to W. The continentalregions are raised while offshore areas aresubsiding, suggesting the occurrence of verticaldifferential movements. The GPS measurementsdocument the active deformation with differentialmovements of individual blocks northwarddirected,in agreement with the shallowseismicity, as well as with the convergencebetween Sicily and
Lingua originaleEnglish
Numero di pagine2
Stato di pubblicazionePublished - 2018

Fingerprint Entra nei temi di ricerca di 'SEISMOTECTONIC MAP OF THE NORTHERN SICILY CONTINENTAL MARGIN (NSCM) AND IMPLICATIONS FOR GEOHAZARD ASSESSMENT'. Insieme formano una fingerprint unica.

Cita questo