Aftershock: Chilean quake shortened Earth days

A JPL research scientist has hypothesized that the recent magnitude 8.8 earthquake in Chile shortened the length of each Earth day by approximately 1.26 microseconds, or one millionth of a second.

According to Richard Gross, the quake may have also shifted the Earth’s figure axis – the axis about which Earth’s mass is balanced – by some 3 inches.

In comparison, the 2004 magnitude 9.1 Sumatran earthquake shortened the length of an Earth day by 6.8 microseconds, while shifting the planet’s axis by 2.32 milliarcseconds, or 2.76 inches.

“Even though the Chilean earthquake is much smaller than the Sumatran quake, it is predicted to have changed the position of the figure axis by a bit more for two reasons. First, unlike the 2004 Sumatran earthquake, which was located near the equator, the 2010 Chilean earthquake was located in Earth’s mid-latitudes, which makes it more effective in shifting Earth’s figure axis,” explained Gross.

“Second, the fault responsible for the 2010 Chiliean earthquake dips into Earth at a slightly steeper angle than does the fault responsible for the 2004 Sumatran earthquake. This makes the Chile fault more effective in moving Earth’s mass vertically and hence more effective in shifting Earth’s figure axis.”

However, Gross emphasized that the Chile predictions were likely to change as data on the quake was further “refined.”