The Great East Japan Earthquake (東日本大震災)

Areas Affected by Earthquake
Areas Affected by Earthquake

Crooked Letters, Straight Lines - Jottings from the other side of the pond


I wanted to find a graphic that would visualize the scale and intensity of the East Japan Great Earthquake that happened at 14:46:23 (JST) on March 11, 20011. The 9.0 magnitude earthquake lasted for an agonizing six minutes. 


As you can see from the above map, the epicenter was just off the coast of Sendai City (38.322°N 142.369°E) at a depth of 32 km (20 mi). It was accompanied by a tsunami which I’ll write about in another post. 


The blue surrounding area tells us not only the depth but the magnitude of the earthquake. So, the higher the magnitude, the larger the circle. The color denotes the focal depth. If you could capture all of the energy (surface) released by this earthquake, you would have enough to power all of Los Angeles for one year.


Below is the link to the above map which you can see all of the earthquakes and aftershocks to date including many over the magnitude of 6. It is said that these aftershocks might continue for years.


Japan Quake Map


Seismologists categorized it as a “megathrust earthquake.” This means that as the result of the Pacific Plate being forced up under the Okhostsk Plate, the strain was building up. Eventually, the strain was too much and a large part of the Pacific Plate broke free and surged westward under Japan as much as 36.5 meters (120 ft).  As a result, the island of Honshu, Japan’s largest island, shifted east by 2.7 meters (9 ft). 


Even more mind boggling is that the earth’s axis was shifted by as much as 25 cm (9.8 in). It may seem like a lot at first glance. But in terms of the earth as a whole, it’s really tiny. However, the earth will rotate at a different speed affecting the length of the day. But the changes are so minute, you’ll not notice it.


Here’s a podcast by a seismologist explaining the roots of this catastrophic earthquake. 


Though the epicenter was 373 km (232 mi) from Tokyo, the intensity was of such magnitude, it caused damage in Tokyo such as cracked walls and windows and falling bricks and tiles. Several gas tanks at a refinery exploded and caught fire. Below you can watch the skyscrapers in Shinjuku sway from the earthquake.