Expert comment on Japanese earthquake

Bruce Gittings, Vice Chairman Royal Scottish Geographical Society/ University of Edinburgh

By Susannah Radford

Foreign Secretary William Hague says that the Prime Minister sends his condolences to Japan. 

Today’s Japanese earthquake continues to affect the Pacific Basin.  Most of the Basin is on tsunami alert with islands closest to Japan at immediate risk.  In addition to evacuation, the three main Hawaiian airports have been closed and people on the west Pacific Island of Guam are also being evacuated.  In the aftermath of this earthquake, Edinburgh Napier News got expert advice on the damaging effects of the tsunami from Bruce Gittings, Vice Chairman of the Royal Scottish Geographical Society/University of Edinburgh.

“Further investigation reveals that the offshore topography around Taiwan tends to reduce the effects of tsunami.  It may therefore be that Pacific Islands are still at considerable risk.  We won’t know the effects for several hours as the tsunami wave(s) take hours to cross the ocean.”

“Most of these islands are remote and many have few facilities, and certainly not helicopters.  I’m afraid they are very vulnerable.  The Pacific Tsunami Warning Network tries to warn people using sirens and mobile phones, and suggests people move to high ground.  If populations don’t have access to these technologies (small coastal villages on remote islands) then there little can be done I’m afraid.  Current reports suggest the height of the tsunami in Taiwan was small (10 centimetres) so the pacific islands may be OK on this occasion.  If the tsunami were larger (>10m) they would certainly wipe habitation off low-lying islands”.

Gittings confirms that the Japan earthquake is in no way related to the Christchurch earthquake which hit earlier this year in February.  He explains,  “There are a set of fault lines and zones which surround the Pacific Ocean, known as the Ring of Fire.” Pacific Islands are not on the same fault line as Japan either, “Fault lines don’t extend that far.” He adds that  “Follow-on earthquakes would be within a few hundred kilometres of the existing quake.  There are no interactions over thousands of kilometres.”

Not every earthquake causes a tsunami. “Whether a tsunami occurs is dependent on what precisely happens on the sea bed as the ‘quake takes place,” Gittings says, “If an area of seabed falls, this displaces water causing a tsunami. Sometimes the movement is lateral, in which case a tsunami doesn’t occur.”

About 44 people have now been reported dead.  It has just been announced that the tsunami warning has been lifted for Taiwan and New Zealand.