By: Cameron Gillard
On March 11, Japan faced the greatest natural disaster in the country’s history. Leaving more than 27,000 dead or missing and destroying more than 125,000 homes, the 9.0 magnitude earthquake and subsequent tsunami caused massive damage in a matter of hours. How exactly do these natural disasters happen? We break it down for you:
WHAT IS AN EARTHQUAKE?
Earthquakes occur when the earth’s surface moves. This happens because the surface or crust of the earth is made up of pieces called tectonic plates. It’s the collision and the sliding together of these plates or along fault lines created by parts of plates that cause earthquakes. Scientists refer to the actual point where the earthquake begins as the hypocenter. The location directly above the hypocenter is called the epicenter. If they’re powerful enough, earthquakes can cause avalanches, landslides and tsunamis.
HOW ARE THEY MEASURED?
Scientists judge the strength of an earthquake using the Richter scale. This scale measures the amount of seismic energy released by an earthquake. The highest rating on the scale is 10.0. Japan’s earthquake on March 11 was measured at a 9.0.
AFTERSHOCKS
While one earthquake can be devastating enough, aftershocks almost always follow strong earthquakes. An aftershock is a less powerful quake that follows the first. Over time aftershocks will decrease in strength until they eventually stop. If there is ever an aftershock that is more powerful than the main shock, then that quake becomes the main one and the original earthquake becomes a foreshock, which is the same thing as an aftershock—just reversed.
DID YOU KNOW?
While we here in Canada don’t experience many earthquakes, scientists estimate that around 500,000 happen each year, roughly 100,000 of which we actually feel.
TSUNAMIS
Tsunamis are gigantic waves caused by the sudden movement of a large amount of water. The seismic energy released from earthquakes can cause these huge waves that characterize tsunamis. The most destructive tsunamis are usually caused by earthquakes that measure 7.5 or higher on the Richter scale. If powerful enough, one tsunami wave could travel thousands of kilometres in just a matter of hours. On March 11, the tsunami in Japan was strong enough to carry away cars and destroy entire towns.
LANDSLIDES
Like tsunamis, landslides can be another destructive outcome of earthquakes. While not always caused by a quake, landslides are likely to occur in their aftermath if the location is right. Earthquakes help cause these natural disasters in two ways: the first is when added debris from a quake causes a slope to crack, and the other is when the seismic energy from an earthquake “liquefies” or makes the ground lose its strength and fall.
FOR THE RECORDS
Before Japan’s 9.0 quake on March 11, these were the world’s most powerful earthquakes:
5. Arica, Peru (now a part of Chile) – Magnitude: 9
August 13, 1868
4. Kamchatka – Magnitude: 9
November 4, 1952
3. Off the west coast of northern Sumatra – Magnitude: 9.1
December 26, 2004
2. Prince William Sound, Alaska – Magnitude: 9.2
March 28, 1964
1. Chile – Magnitude: 9.5
May 22, 1960