December 22, 2011 – Tokyo Waits for “The Big One” as the Solar Eclipse of May 20, 2012 Moves Ever Closer:
“And the Sun in the sky never wearies
Of spreading his radiance around,
And the Moon in haste eclipsed him
and the Sun in anger swore,
He would curl his wick within him
and give light to you no more.”
Greek Playwright (450BC – 385BC)
From “Chorus of Clouds”
Though the March 11, 2011 Japan earthquake was the largest to strike the country since the dawn of modern seismology, it wasn’t the long dreaded “big one,” experts say.
Not because the magnitude 9 earthquake wasn’t big (it permanently moved Japan 8 feet), but because it was in the wrong place. Seismologists have long predicted that the big one would probably be a repeat of the 1923 Kanto earthquake, which occurred in a dangerous fault zone close to Tokyo and killed an estimated 142,000 people.
Japan is a tectonically complex zone where three major plates, the Pacific plate, the Okhotsk plate, and the Philippine plate are all ramming into each other (see map). The 1923 Tokyo earthquake was generated from the collision between the Philippine plate and the islands of Japan, in a fault zone known as the Sagami Trough, offshore from Tokyo.
The March 11, 2011 earthquake occurred farther north, in the southern part of the Japan Trench, formed by the collision of the Pacific and Okhotsk plates. Most experts didn’t expect one so big from there. That’s because the Japan Trench has always produced big but not monstrous quakes, at least in the thousand years since humans have been keeping track.
Not that the Japan Trench had been seismically inactive. Northern Japan has had earthquakes throughout its history. The problem is that scientists don’t have enough long-term records of past earthquakes to predict the largest possible earthquake from any given location. That’s true even in Japan, where historical records go back more than 1,100 years.
Recent history is no indicator of what could happen. There is still a fear that there will be another big earthquake down south, in the Sagami Trough, near Tokyo.
University of Tokyo earthquake specialist Yasutaka Ikeda has made high-precision GPS measurements of the rate at which tectonic forces are compressing the plates along the Japan Trench. Ikeda compared those measurements to the rate at which tension has been released by earthquakes. “There will be a much larger one in the future,” he said.
No matter how carefully we build, damage resistant structures don’t exist, when faced with the tremendous power of mega-quakes.
The Master of Disaster