Before the ’04 Tsunami, an Earthquake So Violent It Even Shook Gravity

[scott1]

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.

Grace recorded a sudden drop in gravity near the quake’s epicenter off Sumatra.

http://www.nytimes.com/2006/08/08/s...1980f607&ei=5090&partner=rssuserland&emc=rss"
How is it possible to have a drop in gravity when a Earth quake happens?

 

[Danger]

Not my field, but I can't see it happening on the whole. If the quake was big enough, maybe it caused a temporary shift in the centre of gravity. If the satellite was aimed at a small, specific area, maybe there was a local drop.

 

[cesiumfrog]

Aerial measurements of gravity are useful for various purposes, eg. identifying economically feasible ore deposits. Try googling "Gravity Recovery and Climate Experiment"?

 

[Rach3]

A large mass was suddenly displaced, thus the Earth's gravitational field was slightly altered, very suddenly. A planet is not a uniform sphere; there are inhomogenities in mass distribution, which can be mapped by measuring the gravitational field. Look at the picture - the scale is in parts per 10^-5, these are very tiny differnces.

Note carefully - "drop in gravity" is not a change of physics, it's simply the result of a change of topography.