Patrick Maloney, Elena Sava, and Laura McDonald

Tsunamis in Japan

The island nation of Japan is located on the edge of a multitude of tectonic

plates. The southern half of the nation of Japan is located on the eastern edge of the

Eurasian plate while the northern half is situated on the North American plate. To

the West of each of these sit both the Pacific and Philippine plates. Both the

Philippine and Pacific plates of are moving westward, as they subduct beneath the

Eurasian plate and North American plates respectively.1 The seismic activity of

these plates, coupled with volcanic activity from subduction zones have caused

multiple tsunamis that have produced a large number of casualties.

Major and Recent Tsunamis

The tsunami on March 11th 2011 was the most recent Tsunami in Japan.

Triggered by a 9.0 magnitude earthquake that struck off the shore of Honshu, Japan,

this earthquake was the strongest to ever hit Japan in recorded history. The

earrthquake shook the ground around 2:46 PM and shortly after resulted in the

creation of a destructive tsunami. The highest run-up in the ocean was measured

38.9 meters in height.2 The highest tsunami height was 7.3 meters at Soma.

Following these maximums, there were heights of 4.2 and 4.1 in Oarai and Kamaishi

Japan.3 The tsunami was a devastating disaster that caused 15,826 deaths, 5,942

1 http://blogs.agu.org/wildwildscience/2011/03/11/super-quake-spawns-massive-tsunami-in-japan/2 http://www.ngdc.noaa.gov/hazard/tsunami/pdf/2011_0311.pdf3 http://earthobservatory.nasa.gov/IOTD/view.php?id=49621

injuries, and 3,810 people to go missing.4 The tsunami not only caused homes and

buildings to be swept away, but it also took away entire towns.

There were tsunami seawalls that were supposed to nullify tsunami

situations, but no one predicted that a tsunami of such size and force would hit such

a populated area and the walls were rendered useless. The tsunami caused nuclear

power plants to be shut down. One shut down led to a meltdown and caused the

reactors to explode and catch on fire. This caused millions of people to be without

power and radiation to be spilled into the atmosphere and seas of Japan.

Additionally, there was a huge economic impact for Japan and the countries they

trade with. The cost of the damage was estimated to be $300 billion dollars.5 People

around the world are still trying to clean up from the disaster. As a result, March 11th

2011 will be a day never forgotten in Japan’s history.

Before and After tsunami photo of Arahama Beach, Sendai, Japan.6

4 http://en.wikipedia.org/wiki/2011_T%C5%8Dhoku_earthquake_and_tsunami5http://en.wikipedia.org/wiki/Aftermath_of_the_2011_T%C5%8Dhoku_earthquake_and_tsunami6 http://walrus.wr.usgs.gov/news/sendai.html

Destruction from the tsunamis7 Propagation of waves from the earthquake.8

The Mount Unzen volcanic eruption of 1792 caused a landslide, which

brought about a destructive tsunami. The volcano is located on the island of Kyushu

which is approximately 40 km East of Nagasaki. About a month after the eruption of

the volcano, Mount Mayuyama collapsed creating a landslide that cascaded into the

Ariake Sea at a speed of 200 kilometers per hour. The landslide debris displaced a

vast amount of water in the sea causing a “megatsunami.” A megatsunami is a

tsunami that has much larger wave heights then normal tsunamis and usually

originates from landslides or impact events.9 This tsunami reached 100 meters

high. It was quite detrimental, killing about 15,000 people.10

7http://www.nydailynews.com/news/world/galleries/earthquake_tsunami_strike_japan/earthquake_tsunami_strike_japan.html8 http://nctr.pmel.noaa.gov/honshu20110311/Energy_plot20110311-1000.png9 http://en.wikipedia.org/wiki/Megatsunami10 http://vulcan.wr.usgs.gov/Volcanoes/Japan/description_unzen.html

Picture of the aftermath of the landslide11

The Sagami Gulf is located South of Kanagawa Prefecture in Honshu, and is

approximately 40 km southwest of Tokyo. In 1923, the Sagami Gulf earthquake caused

over 99,000 deaths and generated a tsunami that caused over 2,000 deaths. With a height

of 39.5 feet, the tsunami reached the gulf of Sagami and destroyed over 155 houses and

killed 60 people. This left about 1.9 million people homeless, while others had to

evacuate on a ship that transported them as far away as the port of Kobe. The earthquake

was strong enough to be felt in Los Angeles and Coos Bay, Oregon. The damages are

estimated to have exceeded one billion U.S. dollars at present day value.12

Wave Propogation

11http://www.peepat.com/blog/top_ten/top_10_deadliest_volcanic_eruptions_of_the_world.aspx12 http://www.britannica.com/EBchecked/topic/1421140/Tokyo-Yokohama-earthquake-of-1923