More than 700 people died and two million are estimated to have been affected by the 8.8-magnitude tremor and subsequent tsunamis.
The quake, the most powerful to hit the nation in 50 years, sent shockwaves out from the epicentre 70 miles from Chile's second city, Concepcion.
Buildings and roads collapsed and 500,000 homes have been left severely damaged.
Six aid workers died when a plane carrying them to Concepcion crashed.
The team was on its way to help organise accommodation for those left homeless by the disaster.
Soldiers were sent to patrol Concepcion's streets after mobs set fire to shops and started looting them, hindering attempts to rescue survivors.
If the planet's axis did shift by 8cm during the quake, days would have shortened by 1.26 microseconds, Mr Gross calculated.
A microsecond is one-millionth of a second.
Earth days are 24 hours long because that is the amount of time it takes the planet to make one full rotation on its axis, so shifting the axis would affect rotation.
The quake shifted the Earth's axis by even more than the 9.1-magnitude tremor off Indonesia that started the deadly tsunami in Asia in 2004, according to Mr Gross.
This was partly because the fault line responsible for the quake in Chile "dips into Earth at a slightly steeper angle than does the fault responsible for the 2004 Sumatran earthquake", he said.
The different angle made Saturday's tremor more effective at moving Earth's mass vertically and shifting the planet's axis, Mr Gross continued.
The 2004 quake in Asia, which killed hundreds of thousands of people, caused the Earth to move by around 7cm.
It chopped an estimated 6.8 microseconds off the length of a day, Nasa said. (source Yahoo.com)
Spoiler!
, earth tilts away from sun now so the few degrees we warmed will be cooled down
