led around the globe -- twice, a Japanese observatory said Friday. The Matsushiro Seismological Observatory, north of Tokyo, detected surface quake waves at 3:41pm Japanese time (0641 GMT) Monday, some 13 minutes after the 7.9-magnitude quake struck in China's Sichuan province.
Seismological equipment in an underground tunnel showed the same kind of low-frequency waves 90 minutes later at 6:10pm and again at 8:40pm, according to the observatory.
This shows the waves from the quake went round the globe twice, travelling eastward from the epicenter to Japan, crossing the Pacific to the Americas and the Atlantic Ocean to Africa before coming back to Asia, it said.
Westbound waves were also observed, it added.
"The circling of waves was observed as the quake was so intense," Matsushiro observatory chief Naoya Mikami told AFP by telephone.
A huge fault, or a break in the Earth crust, caused the earthquake, sending strong seismic waves, he said, adding that usually only surface waves from a quake of about magnitude 8.0 or stronger go around the globe more than once.
Surface waves, which cannot be felt by humans, travel more slowly and last longer than waves that go through the interior of the Earth.
