A research team from Durham University and two other institutions analysed the distribution of mud, sand and peat within subsoil samples and sediment sequences at sites along the Gulf of Alaska coast. The data provided a record of earthquake events going back 2,000 years.

The results suggest that earthquakes in the region may rupture even larger segments of the coast and sea floor than previously thought. In 1964, the Alaksan earthquake, the second-largest ever recorded, triggered tsunamis as high as 52 metres. The new research suggests that a more extensive earthquake may create even bigger tsunamis. Although warning systems are in place on the west coast of North America, the findings suggest that evacuation plans should be reviewed.

‘Our radiocarbon-dated samples suggest that previous earthquakes were 15 per cent bigger in terms of the area affected than the 1964 event,’ said lead author Professor Ian Shennan.  ‘The region has been hit by large single-event earthquakes and tsunamis before, and our evidence indicates that multiple and more extensive ruptures can happen.’

‘The energy imparted to the tsunami will be larger but spread out over a longer distance [so it] will have more of an effect on areas farther from the source, such as southeastern Alaska, British Columbia, and the US west coast,’ said Professor Ron Bruhn of the University of Utah. The study was published in Quaternary Science Reviews.

Rebecca Yap
October 2009v