Release of mineral-bound water prior to subduction tied to shallow seismogenic slip off Sumatra

Trying to understand where major earthquakes and tsunamis might occur requires analysis of the sediments pouring into a subduction zone. Thick sediments were expected to limit earthquake and tsunami size in the Sumatran megathrust event in 2004, but the magnitude 9.2 earthquake defied expectations. Hüpers et al. analyzed sediments recovered from the Sumatran megathrust. They found evidence of sediment dehydration, which increased fault strength and allowed for the much larger earthquake to occur. Thus, models of other subduction zones, such as the Gulf of Alaska, may underestimate the maximum earthquake magnitude and tsunami risk