When the ground in Japan started shaking on March 11, 2011, the Japanese, who are well accustomed to earthquakes, knew this time was different.
They weren’t surprised—the fault that ruptured has a long record of activity. But this time the trembling continued for six minutes. When it finished, many turned their eyes to the sea off the country’s craggy and quake-scarred coast, as they are taught, and waited for the waves to come.
But the last time something remotely similar had happened was more than 1,000 years ago and, even in a country that prides itself on its shared cultural memory of the distant past, that event had been largely forgotten. Since that time, much has changed.
People and development have sprung up along the coast, along with a string of nuclear reactors.
Everything, it seemed, had changed in the intervening millennium—except the ocean. Compared with other large earthquakes in recent memory, the magnitude 9.0 Tohoku earthquake, as it became known, was different in many ways.
The temblors off Chile in 2010 (magnitude 8.8) and Sumatra in 2004 (magnitude 9.1) involved faults that extended partly onto land, but the Tohoku earthquake occurred entirely beneath the ocean—nearly 5 miles beneath the sea surface in some places.
In Japan, the combination of natural forces and greater human presence created a domino-like sequence of events, from earthquake to tsunami to the release of radiation from the mangled remains of the nuclear power plant near Fukushima.
The majority of these events played out in the ocean, noted Jian Lin, a seismologist at Woods Hole Oceanographic Institution (WHOI).
The Tohoku earthquake also triggered a cascade of scientific dominoes, as geologists, geophysicists, chemists, modelers, physical oceanographers, and marine biologists mobilized to understand the causes and consequences of the earth quake.