Tsunami theories range from the constructive to the crackpot, John Huxley discovers.
More than a month after the world's most devastating tsunami, the aftershocks keep coming. Planet Earth is still reverberating, "ringing like a bell". And the waters of the Indian Ocean continue to slosh between the west coast of Australia and the distant east coast of Africa.
Scientists are also convinced that the huge earthquake that preceded the tsunami shifted the North Pole, altered the planet's shape and speeded its rotation, decreasing the length of the day - although the precise magnitude of such changes is still being calculated.
These are just a few of the findings being made by scientists around the world investigating the event with the aid of unprecedented data, witness accounts and theories ranging from the constructive to the crackpot, the mainstream to the mythological.
"A great deal remains to be learned," says Herb McQueen, from the Australian National University in Canberra.
"The human impact of this particular event has been a terrible tragedy but geoscientists have been anticipating a big earthquake like this since the last ones in the 1960s. It is the first to have been measured with the new generation of sophisticated technology."
Dr McQueen, who has been measuring vibrations of the earth on a gravity meter in a fireproof basement beneath Mount Stromlo Observatory near Canberra, likens the disaster to a light suddenly flashing in a dark room. "It's only a quick glimpse. But especially with sensitive networks of measuring instruments in place round the world, such brief flashes provide much about what we know about the structure of our planet."
In terms of the planet, Dr McQueen compares the difference between the magnitude 9.0 quake and more common large quakes to "tapping a bell with a spoon and belting it with a hammer".
The oscillations "would not throw people out of their chairs", being about one-tenth of a millimetre of vertical motion, but they continue long after the event.
So, too, does the movement of the Indian Ocean. "It's almost stopped but the ocean does slosh around for quite a while," explained John Church, a CSIRO climate-change expert monitoring tidal gauge data from around the world. "It's like tossing a big pebble in a pond ... The topography of the oceans is complex and the effects can be far-reaching and unexpected," he said, pointing to the destruction of bird colonies on islands in the mid-South Atlantic. This is a further indication of the quake's earth-shaking significance.
NASA scientists have calculated the earthquake probably shifted the "mean North Pole" about 2.5 centimetres eastwards, reduced the earth's oblateness (its tendency to flatten on the top and bulge at the equator) and changed its rotation. Like a spinning skater drawing their arms closer to the body, the earth began to spin faster, reducing the length of the day by an estimated 2.69 microseconds (a microsecond is a millionth of a second). Too small to notice, but big enough to prompt some observers to joke that pay rates should be cut in line with the reduction in working hours.
Paul Tregoning, a geophysicist at the ANU, says the quake caused big movements in the earth's crust. He hopes to establish just how big by using data from GPS (global positioning system) recorders throughout Malaysia, Thailand and Indonesia. Early indications suggest the islands of Sumatra and parts of the Malay Peninsula moved to the south-west, while the underlying, oceanic plate moved to the north-east.
Geoscience Australia continues to monitor the aftershocks. Like the ANU's earth sciences team, the agency has been sifting reports of unusual post-tsunami activity by Australians, both amateur and professional.
Last week, on Radio National, the seismologist Mark Leonard addressed reports from the Northern Territory of the level of water rising and falling in a Rum Jungle swimming hole at the time of the earthquake. "Yes, quite credible. The water in the aquifer may be moving in and out of gaps as the earth's crust rose and fell."
This week he answered queries about planetary alignments, concurrent sunspot activity, and about the skittishness or otherwise of animals at the time of the quake (which may, indeed, be more sensitive to the initial wave activity that precedes the damaging, secondary waves).
But some calls, he admits, were fanciful. "A Sydney psychic rang to say that she had started feeling vibrations about the time of the earthquake. She rang back later in a panic to warn us that the vibrations had started again."
Such public reaction - reflected in the current circulation of extravagant conspiracy theories blaming the earthquake on everything from God's displeasure with man to nuclear weapons testing - are not altogether surprising.
Just as scientists have been studying ancient myths in the hope of understanding past events such as tsunami, so sociologists recognise that myth-making is a way in which humans confront the incomprehensible.
