Size and time distributions of landslide events

Conversely from approaches that retrieve the landslide characteristic distribution a posteriori as the best fit of data sets of specific events, we propose a cellular automaton model able to reproduce the landslide size distribution a priori by means of some characteristic parameters. From the comparison between our synthetic probability distribution and the landslide area probability distribution of three landslide inventories, we estimated the typical size of a single cell of our cellular automaton model, ranging from 35 sqm to 100 sqm, which is a crucial information if we are interested in monitoring a test area. We characterize the landslide frequency-size distribution by varying the model parameters and find that to determine the probability of occurrence of a landslide of size s it is crucial to get information about the rate at which the system is approaching instability rather than the nature of the trigger. Another key aspect for hazard prediction is the inter-event occurrence time statistics. The inter-event occurrence time is the interval between events whose sizes are above a given threshold. Analyses of time series of events have shown that the inter-event occurrence time distribution seems to obey a Weibull distribution with the shape parameter less than one. Such a feature suggests temporal clustering of landslide events. We use our cellular automaton model to study whether simulated landslide events are correlated in time.