Articles | Volume 16, issue 3
Nat. Hazards Earth Syst. Sci., 16, 663–674, 2016
https://doi.org/10.5194/nhess-16-663-2016
Nat. Hazards Earth Syst. Sci., 16, 663–674, 2016
https://doi.org/10.5194/nhess-16-663-2016

Research article 09 Mar 2016

Research article | 09 Mar 2016

Inversion kinematics at deep-seated gravity slope deformations revealed by trenching techniques

Federico Pasquaré Mariotto1 and Alessandro Tibaldi2 Federico Pasquaré Mariotto and Alessandro Tibaldi
  • 1Department of Theoretical and Applied Sciences, University of Insubria, Varese, Italy
  • 2Department of Earth and Environmental Sciences, University of Milan-Bicocca, Milan, Italy

Abstract. We compare data from three deep-seated gravitational slope deformations (DSGSDs) where palaeoseismological techniques were applied in artificial trenches. At all trenches, located in metamorphic rocks of the Italian Alps, there is evidence of extensional deformation given by normal movements along slip planes dipping downhill or uphill, and/or fissures, as expected in gravitational failure. However, we document and illustrate – with the aid of trenching – evidence of reverse movements. The reverse slips occurred mostly along the same planes along which normal slip occurred, and they produced drag folds in unconsolidated Holocene sediments as well as the superimposition of substrate rocks on Holocene sediments. The studied trenches indicate that reverse slip might occur not only at the toe portions of DSGSDs but also in their central-upper portions. When the age relationships between the two deformation kinematics can be determined, they clearly indicate that reverse slips postdate normal ones. Our data suggest that, during the development of long-lived DSGSDs, inversion kinematics may occur in different sectors of the unstable rock mass. The inversion is interpreted as due either to locking of the frontal blocks of a DSGSD or to the relative decrease in the rate of downward movement in the frontal blocks with respect to the rear blocks.

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Short summary
Palaeoseismological techniques applied with artificial trenches at three deep-seated gravity slope deformations (DSGSDs) in the Alps document extensional deformation and reverse slips. The data indicate that reverse slip might occur both at the toe and in the central-upper portions of DSGSDs. The reverse slip is interpreted as due either to locking of the frontal blocks of a DSGSD or to the relative decrease in the rate of downward movement in the frontal blocks with respect to the rear blocks.
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