Since the Richter Scale goes from zero to ten, it can be hard to understand why the effects of a 5.1 earthquake can be so different from the effects of a 6.1 quake. It’s because the scale is based on a logarithmic function. Each whole number increase in magnitude represents a tenfold increase in measured amplitude, and in terms of energy, each whole number increase corresponds to an increase of about 31.6 times the amount of energy released. Each increase of 0.2 corresponds to a doubling of the energy released.

Here’s the formula:

where A is the maximum excursion of the Wood-Anderson seismograph, the empirical function A₀ depends only on the epicentral distance of the station, ?.

Okay. Enough math. Just the facts please:

The average rate of motion across the San Andreas Fault Zone is 2 inches a year, about the same rate at which your fingernails grow. Assuming this rate continues, Los Angeles and San Francisco will be adjacent to one another in about 15 million years.

There are about a half million detectable earthquakes in the world each year. 100,000 of those can be felt, and 100 of them cause damage.

From 1975 to 1995 there were only four states in the US that did not have any earthquakes: Florida, Iowa, North Dakota, and Wisconsin.

The world’s deadliest recorded earthquake occurred in 1556 in central China, killing an estimated 830,000 people. In 1976 another deadly earthquake struck in Tangshan, China, where more than 250,000 people were killed.

About 90% of the world’s earthquakes occur in the “Ring of Fire”. This is an earthquake-prone zone surrounding the Pacific Ocean.