Hydrogeochemical changes before and after a major earthquake
On the 26th of December, when many people were enjoying their Christmas break, news from the Indian Ocean of a massive earthquake (9 to 9.2 on the Richter Scale) shook the world. Apart from causing direct damage, the earthquake unleashed tsunamis which caused the most widespread disaster in recent history. The disaster was even more shocking because it was so unexpected and so quick. The death toll so far is 224 000 people and it is still increasing. The true figure may never be known.
The tsunami is a sea wave that results from large-scale seafloor displacements associated with large earthquakes. This tsunami was caused by changes to the bed of the Indian Ocean resulting from the earthquake. (For an in-depth description go to 2004 Indian Ocean earthquake). The relief effort is now underway and people in the effected areas are starting the very difficult task of rebuilding their lives. But the question which now needs to be addressed is: Can we stop this sort of disaster from happening again? The answer may well be yes.
Recently, scientists at Stockholm University in Sweden developed a new method for predicting earthquakes with the help of geochemistry. Their method involves metering the content of certain metals in underground water, as this changes before and after an earthquake. Researcher Alasdair Skelton and his team monitored the chemistry of Ice Age water before and after a major earthquake. The water was sampled from a 1.5 km deep well in northern Iceland and was monitored for 10 weeks before, and one year after, an earthquake which occurred on September 16, 2002. The result showed chemical peaks for iron, chromium, manganese, zinc and copper as early as 10 weeks before the earthquake. The peaks were also there at 5, 3 and 1 week before the earthquake. After the tremor, the levels of the elements returned to normal levels. By comparing this data with laboratory experiments, the scientists concluded that this chemicals were dissolved from the surrounding rock. However, for this to happen the rock needed to be exposed to greater than normal heat, and that hot material could only have come from the deeper layer of the earth's crust. The migration of the 'chemically-fingerprinted water' into the surface could signal changes in the permeability of the Earth's crust caused by the accumulation of energy before the earthquake.
Further studies are still needed, but if the results are shown to be reliable, predictions of the future earthquakes and potential tsunamis could give a vital early warning to those in danger areas.
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