IN 1998, Japanese seismologists noticed deep rumbles in the ground that could not be linked to any earthquakes. They suggested that variations in atmospheric pressure might be causing a drumming on the Earth’s surface, leading to the low-frequency hum.
But Barbara Romanowicz of the University of California at Berkeley was not convinced. “From the beginning, I had a hunch that the oceans might be involved,” she says. “But then I had to prove it somehow.” So she and her colleague Junkee Rhie collected data from networks of seismometers in California and Japan, and worked out the direction the hum signal…
