Publication Date:
2019-10-15
Description:
We reconstruct the sequence of landslides that occurred soon after the beginning
of the December 2002 eruption on the NW flank of Stromboli volcano. Landslides
involved the northeastern part of the Sciara del Fuoco (SdF) slope, an old collapse
scar filled by products of volcanic activity, producing tsunami waves that severely
damaged the coast of the island of Stromboli. Volumes of the mass detached
from the subaerial and submarine slope were quantified by comparing preslide
and postslide slope surfaces obtained by aerophotogrammetric and bathymetric
data, which also allowed, in conjunction with field observations and helicopter
surveys, the reconstruction of geometry and kinematics of landslides. According
to the reconstructed sequence, 2 d after the beginning of the eruption, the upper
part of the NE sector of the SdF slope experienced major displacements (few tens
of meters). Movements propagated downslope and affected the nearshore portion
of the submerged slope without a rapid sliding of the displaced mass into the sea.
The following hours were characterized by a progressive increase of deformations,
localized along shear zones extending over two thirds of the subaerial slope. This
phase proceeded until a submarine slide about 6 ´ 106 m3 in volume occurred,
causing a first tsunami wave. The subaerial mass delimited by the shear zones
and unbuttressed at its foot, then slipped into the sea producing a second tsunami
wave. The main landslide event (and the minor slumps which followed) removed
a volume of about 10 ´ 106 m3 of the infilling deposit, to a thickness of at least 65
m. Hypotheses were formulated on the mechanisms that controlled the different
phases of the instability sequence. Since hydraulic and stress/strain conditions
progressively changed during the slope evolution, the formulated mechanisms
are also based on geotechnical analyses and considerations on the mechanical
behavior of volcaniclastic materials. The process that led to the landslide events was initiated by forces exerted by magma intruded into the slope, while further
steps of the evolution of slope stability conditions (especially the submarine failure)
were controlled by the particular shear behavior of the volcaniclastic material,
mainly influenced by grain crushability. In fact, strength progressively decreased
as shear strains proceeded, and the intensely sheared saturated material forming
the submarine slope may have become susceptible of failure when sudden strain/
stress increments occurred.
Description:
Published
Description:
1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
Description:
reserved
Keywords:
Slope Failures Induced by Eruption
;
05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
book chapter
Permalink
