The major Chile earthquake a few days ago appears to have shortened the length of Earth’s day by 1.26 microseconds (1.26 × 10-6 or 0.00000126 seconds) and moved its axis by about 8 cm (3 in).

How could this happen?

Have you ever spun around in a chair and noticed that moving your arms in or out changed your speed? When you put your arms out you rotate slower and pulling them in makes you spin faster. It would seem that the earthquake caused a notable chunk of Earth’s mass to move closer to the center which caused the spinning Earth to speed up.

Source: Discoblog & CNN