The earthquake prediction is far from being a precise science. Also, everybody hopes that the researchers who publish their analysis of situation geophysics in Sumatra in the magazine Science of this week make a mistake. According to this international team (the United States, Indonesia, Taiwan, Singapore), several large-scale jolts could happen in the course of next decades.

In 2004, when the earth trembled off Indonesia, nobody was ready in this region of the Indian Ocean to manage alert. More than two hundred thousand persons died. Since, the different countries of the region hired an important effort to set up alert. Indonesia establishes itself to be today capable of raising the alarm in less than three minutes. She besides joined the device of surveillance of the preparative Committee of the Organisation of the United Nations for the ban of nuclear tests (CTBTO). This last leans on a network of 337 cells of underground, underwater and atmospheric detections intended to spot nuclear tests.

So improved he is, a network of alert could only reduce human losses in case of big generative seism of tsunami. Because if he happens near the Indonesian coasts, colossal waves would touch the coasts of long before necessary three minutes to raise the alarm. And yet such seisms are announced in the course of next decades by jobs published in Science.

The researchers studied the coral reefs of the islands of Mentawai, in Sumatra. They notice that in this region, the seismic fault of the Probe produced continuation of violent seisms both centuries for seven hundred years. Up to a seism happened in September, 2007 (Magnitude 8,4), the “section of Mentawai”, more than seven hundred kilometres of faults, "slept" since two strong seisms, in 1797 and 1833. According to the researchers, the seism of September, 2007 is the sign which an active period began, that could see happening several seisms, of that one at least of magnitude 8,8. Of what to devastate whole regions of the Indian ocean. «Losses in human lives and damage could equate or exceed those raised in the Indonesian province of Aceh in 2004», write the researchers. Magnitude had then attained 9 …

It remains that to estimate the likelihood of events which happen both centuries from notings down which hit over only the seven centuries is a perilous exercise. What is reassuring, it is that if a huge seism happens in the course of next decades, everybody will still have the memory of the tragedy of 2004. The reflex to take refuge on height will have had no time to dissolve in history.

To know about it more:

• The seism of December 26th, 2004 in Sumatra.
• A booklet which explains the training of tsunamis (in French, format PDF).