University of Pittsburgh Professor of Geophysics Bill Harbert says he has been watching the Honsho region of Japan in recent days. He says there has been a great deal of small earthquakes in the area and he thought a big one might be coming. When he got a text message early this morning that there had been some seismic activity he quickly checked his equipment. What he saw was shockwaves from an 8.9 magnitude earthquake. The shaking continued for about three hours. “When we see these earthquake waves arrive its very difficult to tell whether this is a small earthquake which occurred close to our instruments or a large earthquake that occurred farther away, and when we recorded for three hours we knew in fact this was a very large earthquake,” says Harbert.
Harbert estimates the energy released was equal to that of 336 million tons of TNT. That is 708 times the energy released in the Haiti quake last year. He says it could be the 5th largest quake ever recorded.
As of Friday afternoon Harbert was still seeing after shocks. “I know it is almost impossible to believe but there are aftershocks every three to ten minutes,” says Harbert. Most of them range from five to six on the Richter scale. “They represent no hazard in terms of tsunami or structural damage but I must say, for the people living in this area this would be an extremely difficult time.”
Each line of the above graph is one hour. The lines are labeled in GMT. The minutes appear on the bottom. Harbert estimates the energy released was equal to that of 336 million tons of TNT. That is 708 times the energy released in the Haiti quake last year. He says it could be the 5th largest quake ever recorded. The waves seen on line 17 most likely represent a very small earthquake not far from Pittsburgh. Click the picture to expand.