The earthquake-cum-tsunami packed such fury that it has moved Japan’s main island, Honshu , by about 8 feet. It’s also caused the Earth’s axis to wobble by about 4 inches – something that experts say will lead to the shortening of the day by 1.6 microseconds, or just over a millionth of a second.These very tiny changes happen because of changes in the speed of rotation of the Earth as surface mass gets shifted around in earthquakes, says Patrick Dasgupta, professor of astrophysics in Delhi University.As portions of the Earth’s surface shift, there is a bit of an extra wobble in the planet’s rotation around its axis. This causes an increase in the speed of spinning, resulting in shortening of the day, said Dasgupta. This, however, will have no impact on life on Earth, he added.The 2004 Asian tsunami had clipped the Earth’s day by 6.8 microseconds and shifted its axis by about 3 inches. The Chilean quake of 2010 too shortened the day by 1.26 microseconds and changed the axis by 3 inches.The shifting of islands was observed in the 2004 tsunami too. The southern Nicobar group of islands saw permanent subsidence of about 15 feet while the northern Andaman Islands rose by up to five feet.After the 2004 quake which caused the Asian tsunami, some of the smaller islands off the coast of Sumatra moved by as much as 20 metres and its north-western tip shifted to the southwest by 36 metres. That temblor was considered more powerful than the recent Japanese one, measuring 9.1 in magnitude.The Japanese quake caused a 400-km-long and 160-km-wide rupture in the Earth’s crust as one tectonic plate dove under another off the coast of northern Japan. This led to an upheaval in the sea above it sending a 30-foot wall of water racing up to 10km inland in Japan and reaching California across the Pacific Ocean 10 hours later. Several small island states in the Pacific experienced 2-3 feet high waves, which were ripples of the Japanese tsunami as it went bouncing across the ocean.