Earthquakes and Tsunamies Explained
The recent earthquake and tsunami in Japan provide us with a stark reminder of nature's raw power. Earthquakes, while geologically fascinating, are one of the Earth's most destructive forces. Livescience.com and Graphic.Is have provided several infographics which illustrate how earthquakes and tsunamies work.
The magnitude 8.9 quake that hit 80km off the coast of Sendai, Japan, was caused by one plate slipping under (subducting) another. As one plate moves beneath the other, the upper plate undergoes compression, causing a bulge. Over time, this stress increases until eventually, the bulge collapes, releasing huge amounts of energy. If this happens under the ocean, a huge amount of water is displaced, creating waves that travel very fast (around 500miles per hour). Still, whether or not a tsunami occurs depends on the strength of the earthquake, the direction of the tremblor's motion, and the seafloor topography. At sea, the wave may appear small, but as it approaches land and the water becomes more shallow, the same volume of water tries to move forward - so the wave grows in size (vertically) and eventually crashes in on the land.
For a detailed explanation, please view the infographics below (click them to see the large versions).
Graphic 1: How Tsunamies Occur (image credit: Graphic.Is)
Graphic 2: Anatomy of An Earthquake (image credit: Graphic.Is)
With respect to the Japan quake, you can help by providing information about someone who may have been involved with the disaster using Google's Person Finder. Also, you can donate online or with your mobile phone by visiting the Red Cross website.
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