The great tsunami-generating earthquake of last December has spawned a second great quake, but this time seismologists were looking for it.
John McCloskey of the University of Ulster, U.K., and colleagues had calculated in the 17 March issue of Nature that December's magnitude 9.0 rupture along Indonesia's Sumatran coast had transferred enough stress southward to sharply raise the chances of another large quake on the next segment of the same fault. Lo and behold, a magnitude 8.7 ruptured that section of the fault late Monday local time.
"It is probably correct to say this new earthquake was triggered by the December one," says seismologist Phil Cummins of Geosciences Australia, Canberra, who last year tried to raise concern about the tsunami threat off Indonesia.
As to the tsunami this time around, it's still a no-show at press time. A magnitude 8.7--although only a third as powerful as December's temblor--is still large enough to generate a far-reaching tsunami. This quake was smaller and farther away, but it would also have directed any tsunami more southward, away from Thailand, India, and Sri Lanka toward the great emptiness of the south Indian Ocean. Reports from the Sumatran coast tell of deaths and destruction, but no tsunami.
Across the Bay of Bengal, there was definitely no tsunami. "I am standing where 7000 people died in the December tsunami" says Science's Indian correspondent Pallava Bagla, speaking from the southeast Indian coast. "All is quiet." Residents fled on hearing of the quake, Bagla says, but the wave never came.
More info on the quake from USGS