Japan earthquake: how big was it?

It can be difficult to grasp the power of today's earthquake.The dramatic video and photos coming out of Japan paint a devastating picture. But in order really understand the magnitude of this event, you have to look at the numbers.

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To gain some perspective, the U.S. Geological Survey compared Japan's earthquake with two well known quakes: last year's earthquake in Haiti and the historic 1906 San Francisco quake.

The U.S.G.S. calculated Friday's magnitude 8.9 earthquake in Japan to be 700 times stronger than Haiti's recent magnitude 7.0 earthquake, which devastated Port-au-Prince and killed more than 300,000 people.

When comparing to the 1906 earthquake, the U.S.G.S. has figured that Japan's earthquake is equivalent to 30 of the San Francisco earthquakes. That earthquake, a magnitude 7.7, struck just after 5 in the morning on April 18th. It killed more than 3,000 people and left 225,000 homeless. A total of 28,000 buildings were destroyed.

The 8.9 quake sparked what NOAA is now calling the Honshu tsunami.  Above is a NOAA's representation of how the tsunami was forecast to travel across the Pacific Ocean at a rate of more than 400 miles per hour. Tsunami warnings went up around the Pacific Rim as coastal residents in countries from Japan to the United States fled for higher ground.

Japan's quake now ranks as the fifth most powerful earthquake since 1900. Although the worst of the damage and still-uncertain death toll appears to be limited to Japan, this earthquake has made its mark on world history.