Since 1900, Alaska has had one magnitude 7 or 8 earthquake per year, 45 earthquakes of magnitude 5 or 6, and 10,000 quakes overall annually. In fact, Alaska has 11% of the world's earthquakes, and 3 of the six largest in recorded history were located there.

On May 22, 1960, the most powerful earthquake in recorded history--magnitude 9.5--struck southern Chile. The resulting tsunamis affected southern Chile, Hawaii, Japan, the Philippines, eastern New Zealand, southeast Australia, and the Aleutian Islands.

It is estimated that there are 500,000 detectable earthquakes in the world each year. 100,000 of those can be felt, and 100 of them cause damage.

The Mercalli scale is the lesser known of the two scales to measure earthquakes -- it measures the effects of an earthquake and is distinct from the Richter scale which measures the energy released.

The Richter Scale is logarithmic, which means that each successive whole number represents a 10-fold increase in power. Thus, an earthquake that measures 8 would be 10,000 times stronger than an earthquake that measures 4.

An earthquake's point of initial rupture is called its hypocenter or focus. The epicenter is the point at ground level directly above the hypocenter.

In Norse mythology, earthquakes were explained as the violent struggling of Loki, god of mischief and strife, who murdered Baldr, god of beauty and light, and was punished by being bound in a cave with a poisonous serpent placed above his head dripping venom. Loki's wife Sigyn stood by him with a bowl to catch the poison, but whenever she left to empty the bowl, the poison dripped on Loki's face, forcing him to jerk his head and thrash against his bonds, which caused the earth to tremble.

There are seven major tectonic plates in the world, but there are also fifteen minor plates and many micro plates. Each tectonic plate is approximate 60 miles thick and composed primarily of either continental crust or oceanic crust. These plates are part of the Earth's lithosphere which is comprised of the upper mantle and the crust. The boundaries between plates are where major earth activity occurs, such as volcanoes, earthquakes and the formation of mountains and ocean trenches.

A seismograph, or seismometer, generally consists of a mass attached to a fixed base. During an earthquake, the base moves and the mass does not. The motion of the base with respect to the mass is proportional to the motion of the seismograph relative to the earth, but it can be mathematically converted to a record of the absolute motion of the ground.

Contrary to popular belief, there is no such thing as "earthquake weather". Statistically, there is approximately an equal distribution of earthquakes in all types of weather. While very large low-pressure changes associated with major storm systems (typhoons, hurricanes, etc) are known to trigger episodes of fault slip in the Earth's crust, the number of actual earthquakes triggered by such events are statistically insignificant.