Chilean Earthquake May Have Shortened the Length of a Day on Earth


Yikes! Just how big was the magnitude 8.8 earth quake in Chile? One scientist says the shaking may have affected the entire planet by shifting Earth on its axis. This possibly may have shortened the length of a day on Earth by about 1.26 microseconds. Using a complex model JPL research scientist Richard Gross computed how Earth’s rotation should have changed as a result of the Feb. 27, 2010 quake. If his figures are correct, the quake should have moved Earth’s figure axis (the axis about which Earth’s mass is balanced) by 2.7 milliarcseconds (about 8 centimeters, or 3 inches).

Earth’s figure axis is not the same as its north-south axis; they are offset by about 10 meters (about 33 feet). By comparison, Gross said the same model estimated the 2004 magnitude 9.1 Sumatran earthquake should have shortened the length of day by 6.8 microseconds and shifted Earth’s axis by 2.32 milliarcseconds (about 7 centimeters, or 2.76 inches).

Gross said that 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.

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.

Gross said the Chile predictions will likely change as data on the quake are further refined.

Source: JPL

14 Replies to “Chilean Earthquake May Have Shortened the Length of a Day on Earth”

  1. So if an 8.8 earthquake is roughly equivalent to 400 times the largest nuke ever used, we can actually move the Earth axis?

    Gotta love technology. 😮

  2. Torbjorn: It’s not about the released energy, but about the dislocation of matter – my guess is upward/downward is changing the length of day (as when you are spinning and move your arms to/from your body), north/south is tilting the axis and east/west I dunno.

  3. These gems are always interesting and I like to refer back to previous one using the “Categories” on the RHS.

    This this one be also filed under Earth please Nancy?

  4. What the quake did was to change the moment of inertial of the Earth a tiny bit. It did not change the angular momentum of the Earth, as this was an internal shifting of matter with internal forces. If it did change the angular momentum of Earth then conservation of angular momentum is violated.


  5. When the 9.5 Quake hit Chile in 1960, Alaska had a 9.4 quake 4 years later. This current Chilean quake was 8.8 and I am going to bet that when there is a monster quake in the southern part of the Pacific plate, it will produce another monster quake in the northern fault lines again.

    Let’s predict an 8.0 to 8.5 – ish quake from the San Andreas **area** somewhere between Los Angeles and Bakersfield in the next 12 to 18 months. And it will be from an obscure fault that has had very little attention paid to it by Californicators.
    Anybody up for some inexpensive real estate?? (*,*)

  6. For those who believe tidal forces have a huge influence on earthquakes; does anyone know what the position of the moon was at the time of this event?

    renoor… so you’re saying it isn’t the force of the earthquake which shifts the axis, but rather the displacement of matter outwards or even horizontally?

  7. Well, Mr rudeyd…I hope your prediction doesn’t materialise…

    and Mr Olaf…thank you for sharing an excellent link…
    one of the best I have come across. I shall file it safely.

    best regards to ye all…

  8. @mahesh
    Their Mathematica is one cool calculator with internet realtime access to astronomical and weather data.

    They finally have a version that is barely payable. Still expensive but I am happy with it.

    I miss the simulation module like MatLab.

  9. Almost every other site (including newspapers on my thirld world country) reported only that Earth’s Axis was shifted.

    People inmediately assume Rotational Axis, so it’s nice to see UT didn’t dissapoint!


Comments are closed.