  The rarity of large landslides reduces the number of observations and hinders
the understanding of these phenomena. Runout distance was used here to
determine whether the large landslide deposit formed several thousand years ago
in northern Tahiti was caused by a single or multiple events. Using modelling
to quantify the dynamics of this event suggested that a single event or a small
number of events (n<10) were responsible, and that the maximum slide velocity
was high (>125 m/s) under partially submarine conditions. Such submarine
propagation favoured a slower dynamic but a longer runout. The effective basal
friction under submarine conditions ranged from 0.2 < $\mu$ < 0.3.
