Why Earthquakes Are Hard to Measure Earthquakes are very hard to
measure on a standard scale of size. The problem is like finding
one number for the quality of a baseball pitcher. You can start
with the pitcher's win-loss record, but there are more things to
consider: earned-run average, strikeouts and walks, career
longevity and so on. Baseball statisticians tinker with indexes
that weigh these factors (for more, visit the About Baseball
Guide). Earthquakes are easily as complicated as pitchers. They
are fast or slow. Some are gentle, others are violent. They're
even right-handed or left-handed. They are oriented different
ways—horizontal, vertical, or in between (see Faults in a
Nutshell). They occur in different geologic settings, deep
within continents or out in the ocean. Yet somehow we want a
single meaningful number for ranking the world's earthquakes.
The goal has always been to figure out the total amount of
energy a quake releases, because that tells us profound things
about the dynamics of the Eart