Correction Appended

The giant earthquake that set off a devastating tsunami across the Indian Ocean in December 2004 disrupted the earth enough to change gravity and to deflect satellites passing hundreds of miles above.

Two identical satellites, collectively known as the Gravity Recovery and Climate Experiment, or Grace, travel one behind the other in a polar orbit separated by about 130 miles.

By recording small changes in the distance between them when their orbits are deflected, the satellites provide data used to calculate variations in the earth’s gravitational field.

In a report in the current issue of the journal Science, scientists at Ohio State University and the University of California, Santa Barbara, report that in the aftermath of the magnitude 9.1 earthquake, the largest in four decades, Grace recorded a sudden drop in gravity near the quake’s epicenter off Sumatra.