For the people of earthquake-ravaged Sumatra and much of south-east Asia, the worst may be yet to come. That鈥檚 the message from seismologists who say that Monday鈥檚 magnitude-8.7 quake could be just the first in a series triggered by the earthquake in December that led to the devastating Indian Ocean tsunami. The death toll from Monday鈥檚 quake was unclear as New Scientist went to press.
Two weeks ago, John McCloskey at the University of Ulster, UK, and two colleagues said that December鈥檚 quake had increased the risk of another large earthquake along the Sunda fault off the coast of Sumatra, where the India tectonic plate is subducted beneath the Burma plate (Nature, vol 434, p 291).
鈥淧eople have died, so I wish we had been wrong. But from a scientific point of view, today was a great vindication,鈥� says McCloskey. 鈥淲e know now that earthquakes do communicate.鈥�
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Which is why the region should brace itself for more. Rob McCaffrey, a geophysicist at Rensselaer Polytechnic Institute in New York, likens the Sunda fault to a zipper that is gradually coming undone as each earthquake transfers stress along its length. Future death tolls could dwarf December鈥檚, he warns. If the stress continues to migrate, a large quake could hit the heavily populated island of Java. If accompanied by a tsunami, it would put millions at risk.
Not every underwater quake generates a tsunami, though, says Sandy Steacy, a co-author of the Nature paper. 鈥淎 tsunami is generated by a sudden change in the seafloor,鈥� she explains. 鈥淚f an earthquake doesn鈥檛 break the surface, it won鈥檛 generate a tsunami.鈥� Monday鈥檚 earthquake caused only a relatively small wave.
