Multivariate statistical analysis to investigate the subduction zone parameters favoring the occurrence of giant megathrust earthquakes

The observed maximum magnitude of subduction megathrust earthquakes is highly variable worldwide. One key
question is which conditions, if any, favor the occurrence of giant earthquakes (M w ≥ 8.5). Here we carry out a
multivariate statistical study in order to investigate the factors affecting the maximum magnitude of subduction
megathrust earthquakes. We find that the trench-parallel extent of subduction zones and the thickness of trench
sediments provide the largest discriminating capability between subduction zones that have experienced giant
earthquakes and those having significantly lower maximum magnitude. Monte Carlo simulations show that the
observed spatial distribution of giant earthquakes cannot be explained by pure chance to a statistically sig-
nificant level. We suggest that the combination of a long subduction zone with thick trench sediments likely
promotes a great lateral rupture propagation, characteristic for almost all giant earthquakes.