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在线答疑、课后同类题练习、讲义下载、短信提醒Among the dead in South Asia's tsunami① were many tourists at Sri Lanka's national wildlife park at Yala. But very few of the park's animals - elephants， buffaloes， monkeys and wild cats - appear to have died. There are theories that animals can sense natural disasters and flee to safety. First， it's possible that the animals may have heard the quake before the tsunami hit. The underwater rupture likely produced sound waves known as infrasound② or infrasonic sound. Humans can't hear infrasound， but many animals including dogs， elephants， tigers and pigeons can. A second early warning sign the animals might have sensed is ground vibration③。 The massive quake would have produced vibrational waves known as Rayleigh waves. These vibrations move through the ground like waves move on the surface of the ocean but faster. They travel at ten times the speed of sound. The Rayleigh waves would have reached SriLanka hours before the water hit. Mammals， birds， insects and s
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