By ANDY GELLER

December 28, 2004

Because of Sunday's gargantuan quake, planet Earth is ringing like a church bell.
You can't hear it, but it's being measured at seismic stations around the world, including Columbia University's Lamont-Doherty Earth Observatory in Palisades, N.Y.

It will last for three days, perhaps longer.

The quake, which measured 9.0 on the Richter scale, was caused by the shifting of geological plates along a 600-mile area.

This changed the Earth's mass.

As the mass returns to normal, it moves back and forth, much like a church bell when struck by a tong, said Stony Brook geophysicist Teng-fong Wong.

The phenomenon was observed after the 9.5-magnitude quake in Chile in 1960 and the 9.2 magnitude temblor in Alaska in 1964.