At the light of new geological data integrated with revised seismological data, a detailed and original 3D seismotectonic fault-model of the Campania-Lucania (southern Italy) 1980 earthquake (Mw 6.9) is built. Structural field work was carried over a large area (~2400 Km2 ) along the traces of the Quaternary extensional fault system outcropping within the 1980 earthquakes epicentral area. Long-term and co-seismic fault/slip data were acquired by digital survey using FieldMove application. Three major fault alignments, each one articulated in segments and sections, with characterizing attitude, rake and offset, were identified and stored in a GIS database. The inner and intermediate alignments, e.g. Inner Irpinia (InIF) and Irpinia Faults (IF), dip eastward; the outer alignment, e.g. Lucania Fault (LF), is antithetic with respect to IF. Both the InIF and the IF strike in an average NW-SE direction along the northern and central segments and rotate in direction WNW-ESE/W-E along the southern segments. After nearly 40 years since the 1980 earthquake, relevant co-seismic fault scarps with vertical displacement up to ~1 meter are still well evident. They outcrop prevailingly along the IF trace, for a total discontinuous length of ~35 km, and subordinately along the InIF and the LF. A detailed 3D geometric fault-model, extrapolated to the base of the seismogenic layer, was built with the Move Midland Valley software by integrating the georeferenced fault traces with their section-view trace geometry. The latter was derived from serial seismological sections across the hypocentral area (1980 aftershock data relocated by Scarpa et al. in this conference and ISNet seismic events 2005-2011 ML≤3, from De Matteis et al., 2012), from interpretative geological cross-sections and from a geologic reinterpretation of the CROP 04 profile. A corresponding 3D kinematic model was obtained by stress inversion of fault-slip data and focal mechanisms. The reconstructed 3D earthquake/fault association highlighted that the time-space evolution of the 1980 multi-event earthquake was controlled by an interconnected fault system consisting of the InIF, the IF and LF. The first rupture, at the origin time, propagated from north to south along the NE-dipping IF segments; the second rupture, at 20° sec, activated the N-to-NNE-dipping southern segment of the InIF and/or of the IF; the third rupture, at 40° sec, developed along the antithetic LF. The possible seismogenic role attributed to the southern InIF segment represents one of the novel results of our interpretation and may have strong implication in terms of seismic hazard evaluation.
3D fault model of the Campania-Lucania (southern Italy) 1980 earthquake from new field evidences and seismological data
Bello S.;Lavecchia G.;Brozzetti F.;Cirillo D.;Ferrarini F.
2018-01-01
Abstract
At the light of new geological data integrated with revised seismological data, a detailed and original 3D seismotectonic fault-model of the Campania-Lucania (southern Italy) 1980 earthquake (Mw 6.9) is built. Structural field work was carried over a large area (~2400 Km2 ) along the traces of the Quaternary extensional fault system outcropping within the 1980 earthquakes epicentral area. Long-term and co-seismic fault/slip data were acquired by digital survey using FieldMove application. Three major fault alignments, each one articulated in segments and sections, with characterizing attitude, rake and offset, were identified and stored in a GIS database. The inner and intermediate alignments, e.g. Inner Irpinia (InIF) and Irpinia Faults (IF), dip eastward; the outer alignment, e.g. Lucania Fault (LF), is antithetic with respect to IF. Both the InIF and the IF strike in an average NW-SE direction along the northern and central segments and rotate in direction WNW-ESE/W-E along the southern segments. After nearly 40 years since the 1980 earthquake, relevant co-seismic fault scarps with vertical displacement up to ~1 meter are still well evident. They outcrop prevailingly along the IF trace, for a total discontinuous length of ~35 km, and subordinately along the InIF and the LF. A detailed 3D geometric fault-model, extrapolated to the base of the seismogenic layer, was built with the Move Midland Valley software by integrating the georeferenced fault traces with their section-view trace geometry. The latter was derived from serial seismological sections across the hypocentral area (1980 aftershock data relocated by Scarpa et al. in this conference and ISNet seismic events 2005-2011 ML≤3, from De Matteis et al., 2012), from interpretative geological cross-sections and from a geologic reinterpretation of the CROP 04 profile. A corresponding 3D kinematic model was obtained by stress inversion of fault-slip data and focal mechanisms. The reconstructed 3D earthquake/fault association highlighted that the time-space evolution of the 1980 multi-event earthquake was controlled by an interconnected fault system consisting of the InIF, the IF and LF. The first rupture, at the origin time, propagated from north to south along the NE-dipping IF segments; the second rupture, at 20° sec, activated the N-to-NNE-dipping southern segment of the InIF and/or of the IF; the third rupture, at 40° sec, developed along the antithetic LF. The possible seismogenic role attributed to the southern InIF segment represents one of the novel results of our interpretation and may have strong implication in terms of seismic hazard evaluation.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
