Quaternary basin evolution and present tectonic regime in the area of the 1997-98 Umbria-Marche seismic sequence (central Italy) (Articolo in rivista)

Type
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  • Quaternary basin evolution and present tectonic regime in the area of the 1997-98 Umbria-Marche seismic sequence (central Italy) (Articolo in rivista) (literal)
Anno
  • 2002-01-01T00:00:00+01:00 (literal)
Alternative label
  • Messina P., Galadini F., Galli P., Sposato A. (2002)
    Quaternary basin evolution and present tectonic regime in the area of the 1997-98 Umbria-Marche seismic sequence (central Italy)
    in Geomorphology (Amst.)
    (literal)
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  • Messina P., Galadini F., Galli P., Sposato A. (literal)
Pagina inizio
  • 97 (literal)
Pagina fine
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  • Geomorphology Impact Factor 1.669 (literal)
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  • 42 (literal)
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  • Geological and geomorphological investigations performed in the area affected by the 1997–1998 seismic sequence (Colfiorito and Cesi–San Martino basins, central Italy) permitted the reconstruction of the Quaternary tectonic history of this Apennine sector. Tectonic history may be summarised as follows: (1) origin and evolution of the Quaternary faultbounded Colfiorito and Cesi–San Martino basins with a half-graben style; and (2) decrease of tectonic activity since the Middle Pleistocene and related end of displacement along the surficial expressions of the faults. As a consequence, activity is no longer detectable through fault-related surficial displacements but only through ‘‘continuous’’ deformation spread over the basins. This indicates that the recent tectonic history of the basins resulted from cumulative deformation events similar to those related to the 1997– 1998 earthquake sequence. The main implication of the tectonic history in terms of hazard is that the maximum expected magnitude due to activation of the faults is probably similar to that of the recent seismic events and, therefore, no larger than 6. (literal)
Note
  • ISI Web of Science (WOS) (literal)
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  • 1 2 e 4 CNR 3 Protezione civile (literal)
Titolo
  • Quaternary basin evolution and present tectonic regime in the area of the 1997-98 Umbria-Marche seismic sequence (central Italy) (literal)
Abstract
  • Geological and geomorphological surveys have been performed in the area affected by the 1997–1998 Umbria–Marche seismic sequence (Mmax=6.0) aimed at defining the Quaternary tectonic history and the characteristics of the present tectonic regime. Data have been collected from: (1) the analysis of the remnant landsurfaces by means of aerial photos and field surveys; (2) geological surveys in the Cesi–San Martino basin and in the easternmost sector of the Colfiorito basin in order to identify deformative features affecting the Quaternary deposits; (3) the analysis of boreholes and geo-electrical data (derived from previous surveys performed in the 1960s) in order to reconstruct the top of the pre-Quaternary substratum in the Colfiorito basin. Two different successions of remnant landsurfaces have been identified along the faults bounding the basins to the east, in the hangingwall and the footwall, respectively. The difference accounts for a fault-controlled evolution of the landscape at least during the Upper Pliocene–Early Pleistocene. The deformation affecting the Quaternary deposits and landforms in the investigated basins indicates a decreasing tectonic activity along the master faults since the Middle Pleistocene. Surface deformation due to tectonics is faint and displayed by gentle warping of the landforms during the late Quaternary. As for the basin geometry, subsurface data show that two minor depressions formed in the Colfiorito Basin during the Quaternary, the oldest one close to the fault bounding the basin, while the youngest (and deepest) formed in the inner portion of the basin. Therefore, the present geometry is different from that of other fault-bounded Quaternary depressions of the central Apennines (typically half-graben basins), showing the maximum depth of the substratum in the area close to the master fault. Tectonic history may be summarised as follows: (1) origin of the Quaternary fault-bounded Colfiorito and Cesi–San Martino basins; (2) evolution of the basins with a half-graben style; (3) significant reduction of tectonic activity since the Middle Pleistocene. During the third phase, the evolution of the basins is no longer related to a half-graben style. In the case of the Colfiorito basin, a new depression is superimposed to on the previous half-graben whose evolution is related to the lowering of the inner portion of the basin through warping. Moreover, present activity does not result in fault-related surficial displacements but only in ‘‘continuous’’ deformation spread over the basins. These conclusions have fundamental implications for the seismotectonic framework of the 1997–1998 earthquake sequence. This deformation style is, indeed, in agreement with the coseismic deformation modelled by means of the SAR interferometry analyses carried out by other institutions during the seismic sequence, and with the lack of evident surface faulting related to the mentioned events in the investigated area. This evidence indicates that the evolution of the investigated area since the Middle Pleistocene resulted from the summation of deformative episodes similar to that which occurred during the recent seismic sequence. As a consequence, no earthquakes with magnitude larger than 6 are expected in the area. (literal)
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