About Professor Simon Haslett

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Cardiff, Wales, United Kingdom
Professor of Physical Geography and Pro Vice-Chancellor at the University of Wales and the University of Wales Trinity Saint David.

Monday, 18 November 2013

Did a tsunami occur in the midst of Typhoon Haiyan?

A news article from the Philippines is asking whether a tsunami occurred in the midst of the terrible Typhoon Haiyan on 8th November. Haiyan is purported to be the most intense typhoon to make landfall in history, and it was certainly accompanied by a widespread severe storm surge that devastated coastal communities.

However, a series of four waves are reported to have come ashore at a time when the rain had stopped and the wind had died down. The report came from the coastal town of Basey in Samar Province situated in a bay on the east coast of the island.

An eyewitness recounts that the sea receded some distance, leaving fish stranded on the exposed seabed, followed by the approach of a wave about 10ft (c. 3m) high that inundated the town. A further three waves followed and are reported to have washed away people and property.

Storm surges pile water up at the coastline through strong onshore winds and low atmospheric pressure and are unlikely to allow the sea to recede in the same way that a tsunami does. Although large tsunami are associated with high magnitude earthquakes, they may also be caused through submarine slides, or a combination of both. Examples exist where storms have affected ocean loading and apparently contributed to triggering both earthquakes and submarine slides. Indeed, in the Philippine Sea a link between seasonality and earthquakes has been suggested previously. Therefore, the possibility that a tsunami occurred in the midst of the typhoon, however unlikely it may seem, should not be discounted without further investigation.