Here's why Japan's earthquake was so strong

Surprisingly, it ruptured several areas of a fault that before had ruptured alone

NASA Earth Observatory

The first two hours of Japan's massive magnitude-9.0 earthquake has revealed surprising information about how such huge earthquakes rupture.

By Brett Israel

4/21/2011

The first two hours of Japan's massive magnitude-9.0 earthquake has revealed surprising information about how such huge earthquakes rupture.

The earthquake ruptured several areas of a fault that in the past have ruptured alone, contrary to what many scientists would have predicted. If the earthquake had recruited still more nearby segments where massive aftershocks struck, the quake could have been even bigger, said Eric Kiser, a graduate student at Harvard University in Cambridge, Mass., who presented data on the first few hours of the rupture at the Seismological Society of America meeting held last week in Memphis, Tenn.

The March 11 earthquake is now the fourth-largest ever recorded in the world. The quake struck off the coast of the Tohoku region of Japan, triggering a deadly tsunami that may have killed nearly 30,000 people. The rumbling didn't end with this massive rupture, and it hasn't stopped today. More than 60 aftershocks of magnitude 6.0 or greater have struck the region.

The main rupture lasted more than 3.5 minutes, although most of the energy was released in the first 2 minutes, Kiser told OurAmazingPlanet. The rupture associated with the main shock was about 155 miles long and 109 miles wide, Kiser said.

Then came the aftershocks.

Source

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