Closing the ‘seismic gap’ on tsunami risk

By Robert Glasser

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Western Europe had a rude awakening to the risk of tsunamis on November 1, 1755. The churches of Lisbon were packed with worshippers on All Saints’ Day when an 8.5 magnitude earthquake struck that morning.

Many of those who survived the crumbling ruins and the fires which followed, ran to the docks for safety where they saw the water receding. About 40 minutes after the earthquake, the first tsunami arrived. Waves over 18 metres high swept up the Tagus river drowning thousands of people.

The tsunami also brought destruction to the Algarve, today one of the world’s most popular tourist destinations. There was significant damage in Madeira and across the Azores. The waves struck along the coast of North Africa and as far north as Finland, striking the west coast of Ireland and Cornwall along the way.

The estimated death toll from this terrifying event was 50,000. And now, 262 years later, Portugal is to open a National Tsunami Warning Centre on November 21 which will further augment and strengthen Europe’s existing network of tsunami warning centres under the aegis of UNESCO’s Intergovernmental Oceanographic Commission.

Very few of Europe’s citizens will be aware of the tsunami risk to which they are exposed because of what is known as the “seismic gap” which is a section of a fault that has produced earthquakes in the past but is now quiet.

A gap has also opened up in people’s minds as to the possibility of this deadliest but rare natural hazard affecting them anytime soon.

Along with over 200,000 Asians, some 9,000 tourists, mainly Europeans, died in the 2004 Indian Ocean tsunami, an event for which few people were prepared. There are only a handful of stories which demonstrate that people acted on local knowledge of the tell-tale signs of a tsunami.

Japan is synonymous with global efforts to reduce disaster risk and has a deep understanding of what is required to reduce tsunami risk especially following its most recent experience of the 2011 Great East Japan Earthquake and Tsunami.

World Tsunami Awareness Day, now in its second year, is commemorated every year on November 5, the day in 1854 when a tsunami occurred as a result of the Ansei-Nankai earthquake.

Hamaguchi Goryo, a local leader in the village of Hiromura on the Kii Peninsula, anticipated a tsunami would come when he noticed the lowering of the tide and a rapid decrease in the level of well-water.

He guided his fellow villagers to evacuate to higher ground by setting fire to his precious sheaves of rice, knowing that the villagers would run uphill to help put out the flames. He informed them of the tsunami risk and told them to make sure that everyone left the village for higher ground.

After the destruction caused by the tsunami, he financed the building of a protective five metre high and 600m long embankment. He also planted trees along the coast to mitigate the impacts of future tsunamis.

This early example of community-based disaster preparedness was a four-year project which united the community, and provided job opportunities for villagers whose livelihoods and homes were affected by the tsunami.

His actions epitomize the priorities for action of the Sendai Framework for Disaster Risk Reduction which was adopted in Japan two years ago as a global plan to reduce disaster losses by 2030.

Goryo-san was people-centred and inclusive in his approach. He wanted to reduce loss of life, the numbers of people affected by disasters, economic losses and the threat of future damage to critical infrastructure by building back better.

His actions continue to inspire the people of modern day Hirokawa town in Wakayama Prefecture where the embankment is repaired every year on November 5.

One thing I would like to encourage as we mark this year’s World Tsunami Preparedness Day is global reflection on the possibility of future tsunami events in parts of the world where there has been “a seismic gap”.

The US Geological Survey defines a seismic gap as a section of a fault that has produced earthquakes in the past but is now quiet. We know from the research carried out by Professor Fumihiko Imamura and his team at Tohoku University’s International Research Institute of Disaster Science, that there are several such locations around the Pacific Rim.

Many countries in the North East Atlantic, Mediterranean and connected seas (NEAM) region that would benefit from the service, have yet to subscribe to the Tsunami Early Warning Services currently offered by France, Greece, Italy and Turkey under the coordination of the Intergovernmental Oceanographic Commission of UNESCO.

Good work continues to be done in refining early warnings in the Caribbean, the Indian Ocean and the Pacific. If we want to prevent future disasters, it is vital that we do not allow “a seismic gap” to open up in our awareness of the tsunami threat despite the rare occurrence of such events.