Numerical simulation of the 30--45 ka debris avalanche flow of Montagne Pelée volcano, Martinique: from volcano flank collapse to submarine emplacement
Résumé
We simulate here the emplacement of the debris avalanche generated by the last
flank collapse event of Montagne Pele´e volcano (30–45 ka), Martinique, Lesser Antilles.
Our objective is to assess the maximum distance (i.e., runout) that can be reached by this
type of debris avalanche as a function of the volume involved. Numerical simulations are
performed using two complementary depth-averaged thin-layer continuum models because
no complete models were available in the literature. The first model, SHALTOP, accurately
describes dry granular flows over a 3D topography and may be easily extended to
describe submarine avalanches. The second model, HYSEA, describes the subaerial and
submarine parts of the avalanche as well as its interaction with the water column. However,
HYSEA less accurately describes the thin-layer approximation on the 3D topography.
Simulations were undertaken testing different empirical friction laws and debris avalanche
volume flows. Our study suggests that large collapses (~25 km3) probably occurred in
several times with successive volumes smaller than about 5 km3 entering the sea. This
result provides new constraints on the emplacement processes of debris avalanches associated
with these collapses which can drastically change the related hazard assessment such
as the generated tsunami, in a region known for its seismic and volcanic risks.