Measuring the intensity of Earthquakes

The most well-known method of measuring the intensity of
an earthquake is the Richter scale. The Richter scale is
named after an American seismologist named Charles Francis
Richter, and measures the amount of energy released at the
focus of a quake. It uses a logarithmic scale that runs from "1" to "9." Because this scale is logarithmic, each number is
actually an increase of ten times than the number which
precedes it. Thus, a 7.0 earthquake is ten times more
powerful than a 6.0 and 100 times more powerful than a 5.0.

To allow a greater degree of precision, a decimal equivalent
was provided. At one time it, was believed that an
earthquake with a magnitude of 8.5 was the most powerful
possible but new seismic measuring techniques have revealed
that it is possible to reach 9.5.

Another method of measuring the intensity of earthquakes
was developed at the turn of the century by an Italian
seismologist by the name of Giuseppe Mercalli. The Mercalli
scale measures shaking with gradations from I to XII. Since
the effects of the earthquake diminish with the distance it is
from the focus of the quake (epicenter), the Mercalli rating
depends upon where the measurement is taken. The lowest
rating (I) is one which is felt by very few people and the
highest (XII) is one which causes total destruction. An
earthquake with a magnitude of 3 to 4 on the Richter scale is
roughly equivalent to II to III on the Mercalli scale and a
magnitude 8 to 9 on the Richter scale is roughly equivalent to a XI to XII on the Mercalli scale.