Huh?
By Sam Eaton ⋅ May 4, 2012
Color-coded lines track seismic activity at Tokyo University’s Earthquake Research Center. The yellow and red clumps reveal a small quake in the Tokyo-area district of Tsukuba. (Photo: Sam Eaton)
In a quiet room at Tokyo University, seismologist Shinichi Sakai points to steady, color-coded lines on a digital monitor. The screen displays real-time readings from Japan’s extensive network of seismometers. This is one of the most seismically active countries in the world, and the flat lines show that all is quiet across the region, at least for the moment.
Then, as if on cue, two of the lines start to jump violently, splashing the screen with red and yellow pixels. They’re tracking a very small earthquake, centered just outside of Tokyo.
Sakai says small quakes like this happen about ten thousand times a year in Japan, and for geologists like him, even the small earthquakes are worth paying attention to. He says there’s been a fivefold increase in small tremors around Tokyo since the huge quake off Japan’s northeast coast in March of last year. And that adds up to a mathematical omen for scientists like him.
In January, Sakai and the University’s Earthquake Research Institute crunched the new numbers and came up with a shocking prediction: a 70-percent chance that a major earthquake would hit Tokyo within the next four years.
