What was the cause of this catastrophe?
The initial cause was a giant earthquake, measuring 9.0 on the Richter Scale, which happened 100 miles off the northern shore of the Indonesian island of Sumatra on 26 December. The earthquake triggered a giant wave which swept across the Indian Ocean.
How common are tsunamis in the Indian Ocean?
Tsunamis are rare in the Indian Ocean though there have been seven records of tsunamis set off by earthquakes near Indonesia, Pakistan and at the Bay of Bengal. This is the first multi-ocean tsunami since Krakatoa erupted in 1883.
In the 1990s the United Nation’s International Co-ordination Group for the Tsunami Warning System in the Pacific discussed the danger of tsunamis in both the Indian Ocean and the Caribbean.
In September 1997 it met in Peru to discuss extending the warning network to the Indian Ocean. Nothing concrete resulted.
A seismologist with the Australian geosciences agency, Dr Phil Cummins, told a meeting of the international tsunami group in October 2003 that the international warning network had to be expanded into the Indian Ocean.
Following that Dr Cummins worked on records kept by Dutch colonists in Sumatra discovering that earthquakes in the area had created great ocean-spanning waves in the Indian Ocean. One such followed the great Sumatran earthquake of 1833.
In June 2004 another UN body, the Intergovernmental Oceanographic Commission warned that “the Indian Ocean has a significant threat from both local and distant tsunamis”.
Is there an international warning centre for such tsunamis?
The US Department of Commerce runs the National Oceanic and Atmospheric Administration which runs a Pacific Warning Centre in Hawaii.
They operate an international system of buoys and monitoring systems across the Pacific Ocean alerting countries there to oncoming disasters.
The US has run a monitoring system for half a century. A wider warning system, using buoys equipped with sensors called tsunameters, operates in the Pacific feeding information to the centre in Hawaii and a laboratory in Seattle.
This warning system does not cover the Indian Ocean. Scientists wanted just two buoys with the sensors put in the Indian Ocean. One would have been placed off the coast of Sumatra. Funding was not available. The tsunameter sensors cost just $250,000 each.
Dr Stuart Weinstein monitored the earthquake of 26 December from the Pacific Warning Centre.
He said of that day: “Part of me said I wish it had occurred in the Pacific, because we could have saved an awful lot of people.”
How soon were the authorities aware of the tsunami threat?
The Pacific Warning Centre did monitor the earthquake off Sumatra. Within 45 minutes they were aware of the danger of a giant tidal wave sweeping the Indian Ocean.
The US Navy, the US State Department, the US embassies in Mauritius and Madagascar, the US military base on Diego Garcia and the Australian government all received warnings of the tsunami.
The State Department claimed to have warned the Indian government but they say that they received no such warning.
Similarly in Japan the Matusushiro Seismological Observatory monitored the earthquake. An official at the observatory, Masashi Kobayashi states: “When I found it was in the ocean, I thought the first thing to worry about was a tsunami.”
He says he reported his findings to his superiors. Asked why this did not lead to a warning he replied: “My job is to decide the size and the location of the earthquake epicentre, so it is beyond my job to answer that question.”
No warning was issued to the general population of the region.
Would a tsunami warning have been effective?
The wave movements of a tsunami are easily monitored. It took four hours for it to reach the Indian coast, sufficient time for a warning for people to move away from the coast.
Why did so many people die?
This was a natural disaster but one whose devastation was multiplied many times by globalisation and the lack of spending to provide basic protection.
Elsewhere in this issue of Socialist Worker contributors from Thailand and Sri Lanka explain why tourism has led to a massive increase in the numbers of people living on the edge of the Indian Ocean.
But in the US, Japan and Hong Kong buildings are designed to withstand the impact of a likely tsunami.
Even in the Indian Ocean those inside hotels built for tourists were more likely to survive than those living in shanty towns and buildings lacking concrete.