A sea change for earthquakes

A reconstruction of land movements and changes in sea levels for three massive historic earthquakes in Alaska gives clues that may help scientists forecast future earthquakes and earthquake-triggered tsunami. To be published in this week’s Journal of Quaternary Science¹ the findings should help reduce losses from future catastrophic events.

Investigators Sarah Hamilton and Ian Shennan from the University of Durham, England, studied three earthquakes that occurred around 1400-1500 years ago, about 950-850 years ago, and in 1964 at Kenai, southern Alaska.

They found a pattern of change associated with each earthquake. Land in the area was generally rising, but subsided in the years immediately before each great earthquake. Such pre-seismic land subsidence may be one of the indicators that lead up to a great plate-boundary earthquake. Their data show that while earthquake-induced land subsidence was associated with each earthquake, the exact pattern of this subsidence varied during the different events.

Observations made before and after the 1964 earthquake provide information on how land moved before and after the event, and consequently earlier great earthquakes can be calibrated against this one.

There are other similar investigations underway in Japan and Chile.

“We believe that knowing what happened in these past major earthquakes should help predict future seismic activity in plates like this area of southern Alaska,” says Ian Shennan.