This year, the 5th of November, will mark the first “World Tsunami Awareness Day“, an international effort, spearheaded by the UN to raise awareness of an often underappreciated risk. We are all familiar with the recent deadly tsunamis in Indonesia and Japan, the Boxing Day earthquake was the most deadly disaster in decades, responsible for the deaths of over 260 000 people. Whilst great advances have been made in preparing those areas impacted by that event, such as the Seychelles, Thailand and Banda Aceh, there is still significant work to be done to safeguard populations.
Tsunamis are unlike other natural hazards, they have the ability to impact a wide area, the entire coastline of a country, and large events generated waves that are observed worldwide. This map from the NOAA shows wave heights globally following the Indonesian earthquake and tsunami:
Tsunamis produce global perturbations in the sea surface, and the tsunami in Japan resulted in the death of a man in Oregon, and the disturbance of several Fjords in Norway through the creation of seiches, or standing waves. In addition, this event triggered the release of a “Manhatten-sized iceberg” from Antarctica.
In addition to earthquakes, there are several other ways to generate a tsunami. The least frequent, but potentially the most devastating would be a repeat of the 65 million year old asteroid impact in the Gulf of Mexico. Volcanic Islands are the ideal combination of rapid sedimentation, steep slopes and earthquakes, and there are numerous examples of these islands collapsing and generating waves. This can happen either as the result of an eruption, such as the 1883 eruption of Krakatoa, or as the catastrophic collapse of the side of a volcano such as Cumbre Vieja. This particular example is a popular news story, as it may generate a massive tsunami that could reach the UK, however research at NOC shows that instead of one giant collapse, a series of smaller (<350 km3 material) is more likely, and seriously questions the “mega-tsunami” hypothesis. This article from the Landslide Blog run by Dave Petley has an excellent overview.
A further cause of these devastating events are large submarine landslides. You can read more about my work on the giant Storegga Slide that occurred 8200 years ago in the North Atlantic, generating a wave that was 5m high in Scotland.
Given the potential for tsunamis to impact on almost any section of coastline, how prepared are we? This is the fundamental question for this years World Tsunami Awareness day. This website highlights the international efforts in education and preparedness. A prepared and education population is the best defense against a tsunami, and these efforts include tsunami drills in the Indian Ocean, where 24 countries co-ordinate a drill for disaster response and evacuation. Europe is also involved, with significant improvements in early warning and research into the risk of regional tsunamis.
If you do live in a tsunami prone region, there is a wealth of information available through organizations such as the National Tsunami Hazard Mitigation Program who have a series of information resources available.