The quake and the resulting tsunami killed about 20,000 people, wiped out entire towns and triggered power outages and then meltdowns at the Fukushima nuclear power plant.
It also humbled the scientific community.
Since 2004, earthquake scientists have been caught off guard, or to some extent consternated, by huge killer earthquakes in the Indian Ocean, Haiti, China, Japan and New Zealand.
Now the geologists are in a state of soul-searching. They want to do better, get smarter and help save lives on a shaky planet. But they feel chastened by what happened in Japan and are reexamining their basic assumptions about earthquakes.
Humans can be gifted at perceiving patterns in nature. We can also imagine patterns that do not exist. We can focus our attention on too narrow a frame. It is the special challenge of earthquake scientists that they must contend with terrestrial forces that exist outside the frame of human lifetimes, or even the lifetimes of entire civilizations. Some geologic faults may endure thousands of years of strain before a catastrophic rupture.
“This is a humbling field. If you want to be smug, don’t be an Earth scientist, and certainly don’t be an earthquake researcher,” said Ross Stein of the U.S. Geological Survey.
Seismic hazard maps typically show where earthquakes are most likely to occur over a certain period of time, and the expected maximum intensity. But critics say these maps merely describe what has happened before and have virtually no predictive value. They call it “Texas sharpshooting” — shooting the side of a barn and then drawing a bull’s-eye around the bullet hole.
Defenders of the maps argue that they are better than nothing. Policymakers have to decide where to put resources. Which locations have older buildings that are most in need of seismic retrofitting? How high should a tsunami wall be?
Public officials may say, in effect, we know this map is probably wrong, but we still need it for planning purposes.
If there’s one obvious change in attitude among geophysicists since Japan’s 3/11 disaster, it’s a recognition that huge earthquakes can potentially happen on any subduction zone — any of the places where one tectonic plate is diving beneath another. For many decades, the presumption had been that some subduction zones were significantly more likely to generate a great quake.
As Thorne Lay, a seismologist at the University of California at Santa Cruz, noted in a commentary just published in the journal Nature: “[W]e must allow for the possibility of larger earthquakes in regions where we thought that potential did not exist. That is one difficult lesson that we can consider learned.”