HR: 17:20h
AN: T14C-06    [Abstracts]
TI: Anatomy of a Thrust System From Geological and Seismological Evidence: the Case of the Northern Apennines (Italy)
AU: * Burrato, P
EM: burrato@ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia, Via Vigna Murata, 605, Rome, 00143 Italy
AU: Basili, R
AF: Istituto Nazionale di Geofisica e Vulcanologia, Via Vigna Murata, 605, Rome, 00143 Italy
AU: Vannoli, P
AF: Istituto Nazionale di Geofisica e Vulcanologia, Via Vigna Murata, 605, Rome, 00143 Italy
AU: Valensise, G
AF: Istituto Nazionale di Geofisica e Vulcanologia, Via Vigna Murata, 605, Rome, 00143 Italy
AB: The northern Apennines thrust belt has an arcuate trend made up of several fronts progressively younger to the NE. The youngest are buried in the southern Po Plain, and deform the Marche and the northern Abruzzi coastal regions. Instrumental and historical seismicity, fault plane solutions, and a large dataset of seismic exploration lines testify that blind thrust faults produce significant deformation and moderate-size earthquakes up to M=6.0. In spite of their size, earthquakes can still be damaging and pose a substantial hazard to the population and to the civil and industrial facilities. Slip rates lower than depositional rates, blindness of thrust faults and subtle topographic expression of the active anticlines hinder the identification of individual seismic sources. The detection of the active structures is also made difficult by the low seismic release and by the small number of well constrained instrumental earthquakes. However the drainage network and river and coastal terraces faithfully register the surface deformation. In the subsurface, seismic lines and structural horizons document the recent activity of the thrusts and the geometry of individual faults and of the system. The identification and characterization of the most active thrust fronts is critical for a correct evaluation of the seismic hazard. We tackle this problem by combining seismological data with subsurface geology and geomorphology. We present the result of several transects oriented perpendicular to the chain trend highlighting the longitudinal continuity of activity of the thrust fronts and stressing the existence of gaps and shifts in seismic release. Our study shows that seismogenesis in the Northern Apennines follows well defined structural trends. Moving from W to E, in the southern Po Plain seismicity is mainly concentrated along the emergent Pedeapenninic Thrust Front (PTF), as well as along buried outer fronts, although with a lower moment release. However, activity of the PTF is not continuous along strike. In the Marche coastal region deformed marine terraces and river anomalies highlight the position of active coastal anticlines driven by blind thrusts, associated with historical and instrumental earthquakes. Southward, seismicity becomes sparser, less frequent, of lower magnitude, and distributed over a wider area.
DE: 7223 Seismic hazard assessment and prediction
DE: 7230 Seismicity and seismotectonics
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting