|The catastrophic earthquake and tsunami of 11th March in Japan have again demonstrated the immense power of these natural hazards and raised questions around the world about preparedness to deal with them. So what is the hazard in Ireland and what is being done?
Tsunamis are relatively rare on the Irish coast and in the Atlantic in general because the continents around the ocean have passive margins, apart from small subduction zones in the Caribbean and the South Sandwich microplate. However, historical records and geological evidence indicate that, while tsunamis are low-probability events and very unlikely to be on the scale of the Japanese tsunami, the Irish coast is at risk from tsunamis. Tsunami threats to Ireland include:
- a repeat of the 1755 magnitude 8.6 Lisbon earthquake, which GSI-commissioned modelling predicts could generate waves up to 4m high on the southern Irish coastline (see http://www.defra.gov.uk/environment/flooding/documents/risk/tsunami06.pdf for the full technical report); the seismic zone responsible for this earthquake, and a similar one in 1761 that also produced a tsunami, is a fault zone called the Azores-Gibralter fracture that continues to be active and has had a few relatively large but non-tsunamigenic earthquakes in recent years; the 1755 and 1761 tsunamis were the last authenticated tsunami impacts on the Irish coast; see http://map.ngdc.noaa.gov/website/seg/hazards/viewer.htm for an interactive map database of known tsunamis;
- submarine landslides, such as that which occurred off the Atlantic coast of Canada in 1929 and generated a tsunami that claimed 30 lives in Newfoundland; ancient submarine landslides have been mapped on the Irish continental shelf by the INFOMAR programme that would probably have generated tsunamis;
- earthquakes along the convergent plate margins in the Caribbean, such as the January 2010 Haiti earthquake which generated local tsunamis; larger tsunamis have been produced in historical times and in future could traverse the Atlantic to affect Ireland;
- a future eruption of Cumbre Viejà volcano on La Palma, Canary Islands, which might cause a major coastal landslide and trigger a major tsunami that would impact on both European and North American coastlines.
Since the Indian Ocean tsunami of December 2004, considerable international attention has been directed at establishing an effective international warning system for the world's oceans and seas. The International Oceanographic Commission of UNESCO has established an Intergovernmental Coordination Group to seek to develop a tsunami warning system for the North Eastern Atlantic and Mediterranean (NEAMTWS) (see http://www.ioc-tsunami.org/index.php?option=com_content&view=article&id=10&Itemid=14&lang=en ).
GSI represents Ireland in this group. In parallel with this process, GSI coordinates a multi-agency technical group to develop the Irish contribution to NEAMTWS and a proposal for a national warning system. The group comprises GSI, the Marine Institute, Met Eireann, Dublin Institute for Advanced Studies and the Department of the Environment. Currently, this group is awaiting resolution of issues on the international architecture of NEAMTWS and will reconvene when these are clear.
For general information on tsunamis and tsunami warning systems see http://itic.ioc-unesco.org/
For further information on Ireland's tsunami warning system please contact Brian McConnell at 01 678 2850 or by e-mail.