Fact or Fiction: Earthquakes

According to the National Earthquake Information Center, about 1.4 million earthquakes happen annually. The large majority are microquakes, with a magnitude of 3.0 or less.

Scientists had been studying phenomena like volcanoes and earthquakes for years and finally broke through with the theory of plate tectonics in the mid-20th century.

The number is actually closer to 8,000 a year.

When two plates move away from each other, magma (molten rock) seeps up through the crack.

Yep, those are some of the commonly occurring types of faults, and all of them can cause trouble.

It's definitely more common for an earthquake to occur along plate boundaries, but they can sometimes happen in the middle.

Yes, there is concern that a good number of major cities -- many of which lie in earthquake-prone areas -- aren't ready for a major quake.

The biggest was 9.5, in Valdivia, Chile, in 1960.

An even 7.0 is the cutoff for a major quake, and according to the U.S. Geological Survey, an average of 18 major quakes strike the world every year. There is generally one great earthquake (more than 8.0) each year.

The city of San Francisco shook for a full minute on April 18, 1906. Most estimates put the quake at a magnitude of 7.8.