Monday, 14 March 2011

Shorter days caused by earthquakes?

The powerful earthquake of 11th of March in the island of Honsu (Japan) has shortened the day length in 1.8 µs (microseconds, or millionths of a second), has declared Richard Gross from NASA's JPL in Pasadena, CA (USA). Gross has calculated the change in inertia moment, after the deadly earthquake has changed the distribution of Earth's mass.
The massive earthquake has also affected the geometric axis of our planet, which could have been moved up to 17 cm.
"In theory, anything that redistributes the Earth's mass will change the Earth's rotation," Gross said. "So in principle the smaller aftershocks will also have an effect on the Earth's rotation. But since the aftershocks are smaller their effect will also be smaller."
Gross had also calculated in the past displacements of our axis and variations of our day length, following large earthquakes in Sumatra and Chile.
My question is: Does this actually happened? Do this calculation involve astronomical measures that certify the change, and if so, its magnitude? Is this earthquake strong enough to vary the angular inertia of the planet?
Any insight? Please, comment.
You can read the full story at,


Callan Bentley said...

Just in case you get anyone visiting this blog post who is unfamiliar with the metric system, "ms" in the post refers to "microseconds," not milliseconds, or megaseconds, or (as some will no doubt imagine it) minutes. It's probably important to spell it all out explicitly.

Jorge said...

Thanks Callan for the advise. It should be µs from the beginning, but I typed the wrong ascii code.

As a reminder for any visitor, µs is a fraction of a second equivalent to a millionth of it.

Thanks for you visit!