The American Geophysical Union Meeting is an immense science conference, the largest of its kind in the world. Taking place in the multilevel citadel known as the Moscone Center in downtown San Francisco, it lies within the city’s technological landscape and seedy urban environment. I was fortunate enough to catch the first session of a press conference on the Tohoku earthquake that devastated Japan early this year, in particular its most destructive secondary hazard – the tsunami – that slammed into the east coast killing tens of thousands of people and causing catastrophic damage. Not surprisingly much attention is being given to the earthquake and tsunami at the conference. The first press conference on the disaster focused on technologies that were in place to track the tsunami, but also public risk perception of tsunami events in Japan, which could improve when preparing for future tsunami events in Japan.
Prior to the tsunami in March of this year, there were four DART buoys in place along the coast of Japan. Three of them were owned by the US, while the other one was monitored by Russia. These buoys allowed researchers to see the tsunami 30 min after it first occurred and empirical observations matched modelling of the tsunami according to Dr Eddie Bernard from the Pacific Marine Environment Laboratory in Seattle, Washington. The buoys take measurements from the sea floor, detecting the changes in the weight of the water above it. Bernard thinks that solely reporting tsunami wave heights is insufficient for evacuating populations before a tsunami strikes, instead there should be ‘flood forecasts’ that can inform people about the levels of flooding that will likely occur, but this will vary depending on where people live along the coast line. Also, Bernard argues that flood forecasting cannot be done without the information available from DART. ‘An earthquake shakes the earth for four minutes and a tsunami crashes the Earth for 12 hours’, he said.
‘For the people who deal with this along the coastline for 12 hours, any additional information you can provide them as soon as possible, whether it’s five minutes, 40 minutes or 50 minutes, would have been very useful’.
In Japan, they did receive information that a 3m tsunami was coming, but then experienced a power outage and received nothing further. It was learned later that the tsunami reached up to 40m in height. According to Bernard, DART can forecast floods with up to 80 percent accuracy. Flood forecasting may be the way to go as Prof Satoko Oki a social scientist with the Earthquake Research Institute at the University of Tokyo found that of the people they surveyed who lived in areas hit by the tsunami 60 percent said they would evacuate if a tsunami reached 3m in height. Prior to the Tohoku tsunami, only 38 percent of respondents said they would evacuate. A 2m tsunami is enough to wash away someone’s home on the coast and cause severe structural damage. Oki says news media failed to communicate that lower height tsunamis are still important, changing people’s risk perception of a dangerous tsunami because they focused on the record height and not on the actual risks posed by tsunamis in general. Instead the media should also relay basic information about tsunamis. But it seems that it was the novelty of the Tohoku tsunami, the fact that it was of a record-breaking height that was of interest to news media, not the fact that other tsunamis of less height could lead to the destruction of homes and loss of life.
Youtube video on DART buoy detection of tsunamis.