Japan Quake Shortened The Length Of Day & Shifted Axis

Everyone is aware about the massive destruction caused by the 9.0 magnitude earthquake which struck Japan on March 11. This quake was the largest ever recorded in Japan and is the world's fifth largest earthquake to strike since 1900, according to the US Geological Survey (USGS). We have seen how badly it has devastated Japan. But here I have a different matter to discuss with you.

Richard Gross is a geophysicist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. As per his analysis and theoretical calculations the Japan quake has caused a change in the distribution of the Earth's mass and it has affected Earth’s rotation. Now the change in the speed of Earth’s rotation will ultimately affect the time period of 24 hours of a day.

Gross has performed theoretical calculations based on USGS using a complex model and he determined that the Japan quake has caused the Earth to rotate a bit faster and ultimately caused reduction in length of day by 1.8 microsecond (1microsecond=10^-6 second). Previously he suggested 1.6 microsecond shortening of the day, where based on the latest data he refined his estimates to 1.8 microseconds. But you shouldn’t worry about it as you won’t notice this extremely small difference. And also this is not the first time that such change has occurred.

The last year's 8.8 magnitude earthquake in Chile shortened the length of a day by about 1.26 microseconds while the 9.1 magnitude Sumatran quake of 2004 shortened the day by 6.8 microseconds. It is dependent on the magnitude of the quake that how much it will affect the Earth’s rotation. The calculations also revealed that the quake shifted the position of the Earth's figure axis by about 17 cm (6.69 inches), towards 133 degrees east longitude. Earth’s figure axis is that about which the Earth’s mass is balanced. Earth’s figure axis is different from North-South axis; they are offset by about 10 meters.

Gross pointed out "Earth's rotation changes all the time as a result of not only earthquakes, but also the much larger effects of changes in atmospheric winds and oceanic currents". He added further "Over the course of a year, the length of the day increases and decreases by about a millisecond (10^-3second), or about 550 times larger than the change caused by the Japanese earthquake and the position of Earth's figure axis also changes all the time, by about one meter or about six times more than the change that should have been caused by the Japan quake." [Quote from www.nasa.gov]

The changes due to earthquakes have been too small to measure as compared to those caused due to the larger effects of the atmosphere and ocean. However, the effects from the Japan quake may actually be large enough for scientists to observe. Also the impact from the quake may not be completely over. Their may be some remaining aftershocks which will also contribute to tiny changes to day length.