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Geophysical Research Abstracts
Vol. 20, EGU2018-16050, 2018
EGU General Assembly 2018
© Author(s) 2018. CC Attribution 4.0 license.
DSGSD to rockslide transition at the Saline ridge (Valfurva, Italy)
constrained by dating, remote sensing and time-dependent modelling
Federico Agliardi (1), Federico Riva (1), Giuseppe Cola (2), Margherita Cecilia Spreafico (1), Didier Bourlès (3),
Règis Braucher (3), Chiara Crippa (1), Carlo Rivolta (4), and Giovanni Crosta (1)
(1) Università degli Studi di Milano - Bicocca, Earth and Environmental Sciences, Milano, Italy (federico.agliardi@unimib.it),
(2) Glaciological Service of Lombardy (SGL), Via Motta 45, Vimercate, Italy, (3) Aix-Marseille Université,
CNRS-IRD-Collège de France, UM 34 CEREGE, Technopôle de l’Environnement Arbois-Méditerranée, BP80,13545
Aix-en-Provence, France, (4) Ellegi s.r.l, Corso Magenta 12, Milano, Italy
Deep-seated slope deformations (DSGSD) in alpine environments are characterized by huge volumes and long-
term evolution. They can creep slowly for thousands of years or experience a transition to fast, potentially catas-
trophic rockslides, depending on the pattern and rate of progressive failure driven by rock properties, relief, loading
history, and fluid circulation. The reconstruction of the DSGSDs long-term evolution is thus required to assess their
geohazard potential. Riva et al (2017) proposed that large rock slopes undergo paraglacial progressive failure for
long time after deglaciation, eventually resulting in the differentiation of postglacial rockslides with mature shear
zones and high sensitivity to hydrological forcing. We tested this model at the Saline Ridge, on the NW side of
Mt. Confinale (Central Italian Alps). The 1500 m high slope is affected by an active DSGSD, characterized by a
confined basal shear zone with associated slip >100 m in the upper sector, and by reactivation of inherited fracture
systems as gravitational morpho-structures (Agliardi et al., 2001). The lower slope sector is partially collapsed and
hosts the 20 Mm3Ruinon rockslide. This is suspended on the valley floor and slips at fast seasonally variable rates,
currently representing a major landslide threat (Crosta et al., 2017).
To achieve a complete understanding of slope evolution, we integrated morpho-structural observations, absolute
dating, radar interferometry and numerical modelling. We constrained long-term slope evolution by Cosmic Ray
Exposure dating (CRE), using both 10Be and 26 Al cosmogenic nuclides on quartz extracted from six phyllite sam-
ples from key morpho-structures. We maximized the chronological information by performing Schmidt-hammer
exposure age dating at 21 sites (DSGSD morpho-structures, moraine, rockslide and rock glacier deposits). The
present-day style of slope activity was characterized by performing a long-range (up to 4000 m) reprocessing of
a GB-InSAR monitoring dataset, collected since 2006 to monitor the Ruinon rockslide. Long-range, distributed
GB-InSAR data, acquired at extremely high temporal frequency and spatial resolution (1.5 m in range, 8.6 m
in azimuth), allowed detecting non-linear displacement trends in different slope sectors over a decade. Finally,
we integrated all the observations in a time-dependent numerical framework using DaDyn-RS, a damage-based
creep model considering up-scaled rock mass properties and able to account for the effects of deglaciation and
damage-dependent fluid occurrence (Riva et al., 2017). Our results demonstrate a Late Glacial DSGSD initiation
and an early Holocene rockslide nucleation inside a continuously evolving DSGSD, with increasing strain local-
ization, deformation rates and sensitivity to external agents. Our approach allows to effectively identify DSGSD
with potential progressive evolution, and prioritize site-specific monitoring and Early Warning studies.
Agliardi, F., Crosta, G., & Zanchi, A. (2001). Structural constraints on deep-seated slope deformation kinematics.
Engineering Geology, 59(1), 83-102.
Crosta, G. B., Agliardi, F., Rivolta, C., Alberti, S., & Dei Cas, L. (2017). Long-term evolution and early warning
strategies for complex rockslides by real-time monitoring. Landslides, 1-18.
Riva, F., Agliardi, F., Amitrano, D., & Crosta, G. B. (2017). Damage-based time-dependent modelling of
paraglacial to postglacial progressive failure of large rock slopes. JGR: Earth Surface. doi: 10.1002/2017JF004423
