IASPEI - Picture Gallery

IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy
(S) - IASPEI - International Association of Seismology and Physics of the Earth's
Interior
JSS014 Poster presentation 2322
Crustal structure of the Abruzzo Apennines (Central Italy) through the
analysis of seismic data registered by a local network
Dr. Samer Bagh
Centro Nazionale Terremoti Istituto Nazionale di Geofisica e Vulcanologia
Claudio Chiarabba, Pasquale De Gori, Nicola Piana Agostinetti
In this study the background seismic activity and crustal structure of the Abruzzo Apennines (Central
Italy) were investigated by analyzing and processing about 850 local earthquakes and 30 teleseisms,
recorded from April 2003 to September 2004 by a dense temporary seismic network, composed of 30
digital three-component stations. Velocity models computed by local earthquake tomography and
receiver function analysis were used to investigate the crustal structure of the study region. The
computed 3-D tomographic model shows two clear, high Vp features. The shape of the shallower one
(down to 9-10 km depth), resembles in cross section thrust-sheets with E to NE vergence, in good
agreement with the imbricates of the regional thrust systems of the Abruzzo Apennines. The geometry
of this high-Vp anomaly suggests multiple detachment levels, implying a thin-skinned component in the
Mio-Pliocene orogenic building of the region. The deeper high Vp feature, visible between 9 and 15 km
depth (i.e., the lowermost limit of the Vp model resolution), has higher velocities (> 7 km/s). This
relatively thick high Vp feature may represent thick Triassic successions (evaporites and dolomites)
deposited in the hanging-wall of pre-orogenic extensional faults. This suggests a tectonic inversion
component in the compressive tectonics, which may indicate an involvement of, at least, the basementtop
formation in the compressive tectonics. S-wave velocity model obtained by the receiver function
analysis provides valuable information on the basement depth. A low velocity layer (Vs = 2.8 km/s, Vp
= 5.0 km/s) is imaged at about 15 km depth. This layer is interpreted as Permo-Triassic clastic
successions overlying the crystalline metamorphic basement. Based on the obtained velocity structure
and other available geophysical data, a structural model including elements of both thin and thickskinned
tectonics is suggested for this sector of the Apennines.
Keywords: local earthquake tomography, receiver function, crustal structure