Do Earthquakes Affect the Earth’s Rotation? How?

Sam Schechner in Slate:

In covering the massive, tsunami-generating earthquake off the northwest coast of Sumatra this weekend, many news outlets picked up a statement from Enzo Boschi, head of Italy’s National Institute of Geophysics, saying the temblor was strong enough to disturb the Earth’s rotation. Can an earthquake really affect the way the planet spins on its axis?

More here.