The Boxing Day Tsunami Flashcards
Tsunamis occur where…
- earthquakes measure more than 6.5 on the Richter scale
- the earthquake’s focus is shallow beneath the Earth’s surface
- the focus is also beneath the ocean
What was the strength of the earthquake?
The earthquake that caused the Boxing Day tsunami was estimated at between 9.0 and 9.3 on the Richter scale, was over 100 times stronger than the one which caused the Kobe earthquake in 1995.
How high was the sea raised?
The thrust heaved the floor of the Indian Ocean towards Indonesia by about 15 metres, and, in so doing, sent out shock waves. These radiated out in a series of ripples, almost moving unnoticed across oceans until they hit land. The longer and shallower the coastal approach the more the ripples built up height.
How high were the waves that struck?
The waves that struck the shallow coastline near Banda Aceh and parts of Sri Lanka, were nearly 17 metres high on impact. By contrast, islands in the Maldives experienced a four metre high sea swell, rather than a crashing wall of water.
Factors that affect the death toll:
Proximity to earthquake epicentre (affects size of waves and warning time).
Population density in coastal areas.
Ability of government/ authorities to warn people.
Presence or absence of mangrove swamps.
Presence or absence of coral reefs.
Level of tourist development.
Secrecy of Government.
Factors that increased people’s vulnerability in Sri Lanka:
Whether they were indoors at the time of the tsunami (13.8% of casualties). Women and children were more likely to be inside on the morning of the tsunami. Even compared with those on the beach in the sea, people at home were more likely to die.
The quality of the building there were in either in terms of its structure or its location and exposure to the full force of the waves. 14% of deaths occurred in buildings which were completely destroyed, compared to 5% which occurred in buildings that help up well or withstand the initial impact.
