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Integration of geological and geophysical data along a section crossing the region of the 1997-98 Umbria-Marche earthquake (Italy)
Language
English
Obiettivo Specifico
3.2. Tettonica attiva
Status
Published
Peer review journal
Yes
Title of the book
Issue/vol(year)
Vol. Spec. 1 (2002)
Publisher
Società Geologica Italiana
Pages (printed)
891-900
Issued date
2002
Abstract
A geological cross-section, oriented about N80°E and crossing the Colfiorito area, struck by the 1997-98 Umbria-Marche earthquaks has been built up, integrating
surface geological data (field mapping, 1:10.000 scale) and the interpretation of a
seismic reflection profile, kindly provided by Eni-Agip Division.
The section extends from the Umbra Valley Basin, west of Assisi, through the M.Subasio anticline, the Topino valley syncline and the “Inner Ridge” of the Umbria-
Marche Apennines; the latter consists of seven box-shaped anticlines, with a
wavelength of about 3 km. The seismic profile shows that at least the shallower part of the Basement is involved in the compressional structures, forming three steps
stacked at depths ranging from 5 to 8 km, located between the M.Subasio anticline and the “Inner Ridge” of the Umbria-Marche Apennines. The interpreted section also allows a reconstruction of the deep geometry of the presumably active faults bounding the Colfiorito, Annifo and S.Martino basins.
These faults trend N140°+_10°, dip towards SW at ~40°, to a depth of 8-9 km. The faults geometry is comparable with that suggested by the seismological data (focal
mechanisms and aftershocks hypocenters) recorded during the 1997-98 seismic events. Seismicity seems to be confined above the top of the Basement: this
lithological and mechanical discontinuity is suitable to be the base of the seismogenic layer in this region.
surface geological data (field mapping, 1:10.000 scale) and the interpretation of a
seismic reflection profile, kindly provided by Eni-Agip Division.
The section extends from the Umbra Valley Basin, west of Assisi, through the M.Subasio anticline, the Topino valley syncline and the “Inner Ridge” of the Umbria-
Marche Apennines; the latter consists of seven box-shaped anticlines, with a
wavelength of about 3 km. The seismic profile shows that at least the shallower part of the Basement is involved in the compressional structures, forming three steps
stacked at depths ranging from 5 to 8 km, located between the M.Subasio anticline and the “Inner Ridge” of the Umbria-Marche Apennines. The interpreted section also allows a reconstruction of the deep geometry of the presumably active faults bounding the Colfiorito, Annifo and S.Martino basins.
These faults trend N140°+_10°, dip towards SW at ~40°, to a depth of 8-9 km. The faults geometry is comparable with that suggested by the seismological data (focal
mechanisms and aftershocks hypocenters) recorded during the 1997-98 seismic events. Seismicity seems to be confined above the top of the Basement: this
lithological and mechanical discontinuity is suitable to be the base of the seismogenic layer in this region.
Type
article
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