When the devastating 9.0 earthquake struck off Japan’s east coast Friday, it was so powerful it not only shifted Japan’s largest island eastward by 2.4 metres but it shifted the Earth’s axis by 25 cm.
According to NASA’s Jet Propulsion Laboratory in Pasadena, California, it actually accelerated Earth’s spin by 1.8 microseconds, shortening the length of the 24-hour day. It was the largest quake ever recorded in Japan and it is the world’s fifth largest earthquake since 1900, according to the U.S. Geological Survey.
The earthquake happened 130 kilometres east of Sendai, Honshu, Japan, triggering a 10 metre tsunami racing toward land and crushing everything in its path.
Japan sits in the most seismically active place in the world and the country accounts for 20 per cent of quakes worldwide of a magnitude 6.0 or greater. Japan is reputed to be the most earthquake-prepared nation in the world.
But they didn’t expect the ravaging destruction of this one, despite the foreshocks (only recognized in hindsight). According to the Crisis Response Journal, exactly a week before Friday’s quake there was a magnitude 7.2 shaker on March 9th just 40 kilometres from the 9.0 earthquake last week. A further three earthquakes of 6.0 also happened on March 9th.
Even the aftershocks last Friday were huge. Six of them happened within 75 minutes of the great quake and all of them were equal or bigger than the magnitude 6.3 quake in Christchurch, New Zealand last month. Just for the record, Friday’s quake was 8,000 times more powerful than the one in Christchurch. The largest aftershock was 7.1, larger than Haiti’s crushing quake (7.0) in January 2010.
Estimates are that the earthquake could have fractured the fault line for about 500 kilometres. The fault line is where the Pacific plate is subducting beneath Japan and the North American plate. That section of Japan directly affected by the earthquake sits on the furthest western tongue of the North American plate that stretches from Central America and the mid Atlantic all the way north to encompass all of North America, Greenland, and Siberia then stretching down in a sliver along the far western Pacific coastline to press against the Philippine plate right off the coast of north eastern Japan.
While the earthquake’s epicentre was well out to sea, its depth at 24 kilometres was pretty shallow. So as the water was violently displaced with the vertical fracturing, it moved rapidly, producing the long, deadly tsunami that raced to Japan’s north eastern shores at the speed of a jet airliner to unleash its destruction.
The images are heartbreaking. No one in its path stood a chance. Thousands of cars, homes, buildings and ships were devoured in seconds. Four whole trains disappeared. Over 15,000 people are missing; nearly 2,000 are confirmed dead in addition to another 2,000 bodies that have washed ashore. Meanwhile, over a million people are without power and water, roads, bridges and railways are damaged, food and medical supplies are becoming scarce, gas stations are closed and there is a real fear over radiation exposure from damage to three reactors at the Fukushima Daiichi nuclear power plant where cooling systems have failed. Workers desperately tried to cool the core by pumping in sea water but yesterday that too failed when the pump ran out of fuel. As a result, the fuel rods became fully exposed for a couple of hours. Too long an exposure can damage the fuel rods, risking overheating and meltdown.
Watching the Japanese bravely cope with their big one as international help arrives, the question comes up, as it always does, as to when our big earthquake will happen.
Are we ready for this?
