Understanding Earthquakes
It is so hard to understand the differences in the destructive power of earthquakes, because the Richter Scale is a base-10 logarithmic scale that doesn't relate to the ordinary things around us.
I guess it's because of the fact that you don't just easily relate it to anything else with which we are familiar.
I can tell you a 4.7 quake is like hitting a wall at 50 miles an hour, and a 6.7 quake is like hitting the same wall at 45,000 miles an hour.
A brief look at a few examples shows that 2 - 2.9 quake is recordable, a 3 - 3.9 quake can be felt, but damage is unlikely. A 4 - 4.9 quake is noticeable, and produces damage. When we hit the 5 to 5.9 scale, this is considered moderate, and can cause major damage to poorly constructed buildings. A 6 - 6.9 quake is ranked as strong, and can be quite destructive, and a 7 to 7.9 quake is considered to be major, and can cause a lot of damage over large areas. From eight on the scale and up quakes can be devastating, and no earthquake has ever been recorded at a 10.
The largest earthquake in the world was a 9.5 magnitude recorded in Chile on May 22, 1960.
The largest quake in the United States was in Anchorage, Alaska on March 28th, 1964, and was a magnitude 9.2.
If you consider that a 4.0 quake is roughly equal to a one kiloton explosion of TNT, and a 5.0 magnitude is equal to 32 kilotons of TNT (Nagasaki, Japan atomic bomb), the Haiti quake would be like 32 megatons of TNT, and the San Francisco quake of 1906 would be ONE GIGATON, and that was an 8.0 magnitude.
The 2010 Chile quake is equivalent to 15.9 gigatons of TNT.
Maybe an easier example is that a 6.7 magnitude earthquake is 900 times stronger than a 4.7 quake. In other words, a 6.7 quake is equivalent to 900 4.7 magnitude quakes in the effect it will have!
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