What Causes Earthquakes?

Introduction
What causes earthquakes? Earthquakes are vibrations inside the Earth that follow the release of energy that has built up inside rocks. Rocks fracturing, volcanoes erupting, and man made explosions can all release the energy stored in the rocks.

Loma Prieta earthquake, USGS

Loma Prieta earthquake damage to
homes in Marina District, USGS

P waves and Love waves
All earthquakes produce earthquake waves. There are four types of earthquake waves. P waves are also know as primary waves that travel through all parts of the Earth. Love waves are only produced by the most powerful earthquakes. They travel around the surface of the Earth.

Earthquake zones and megathrust earthquakes
Earthquakes occur in earthquake zones. These zones form around crustal plates. As the plates smash into other plates, move apart and subduct they create earthquake faults. Megathrust earthquakes are associated with subduction zones where powerful earthquakes cause tsunamis.

Great earthquakes
The moment magnitude scale was developed after the 1960 Chile earthquake and the 1964 Alaska earthquake. These were the two most powerful earthquakes of the 20th Century.

New Madrid and Haiti earthquakes
The New Madrid earthquakes occurred in 1811 and 1812 were very powerful quakes that rang bells in Boston. The Haiti earthquake occurred in an area that has large numbers of very powerful earthquakes.

What causes earthquakes
Earthquakes waves radiate outward in all directions from the earthquake focus. The focus is where the rocks first break apart during an earthquake. Earthquake faults are places where two crustal plates are moving together, apart or slipping past each other. Normal faults occur when plates are moving apart and one section of land moves downward.

More Earthquake Links

1960 Chile Earthquake The 1960 Chile earthquake was a magnitude 9.5 the largest earthquake ever recorded!

Earthquake Faults Find out more about fault that go up, down and sideways!

Earthquake Focus Learn where the focus and epicenter of an earthquake are located and exactly what they are?

Haiti Earthquake The devastating Haiti earthquake occurred in a region prone to large earthquakes. Find out why these large earthquakes occur.


P waves Find out more about P Waves that are produced by large and small earthquakes.

Love Waves Find out more about Love waves that can topple tall buildings during large earthquakes!

The Mercalli Scale Did you know there can be twelve different intensities of an earthquake but only one magnitude? Find out why!

Normal Fault Find out why miners often find valuable ore in sites where normal faults have occurred.


Megathrust Earthquake Find out why megathrust earthquakes will occur off the coasts of Alaska, Washington, Oregon and California in the future.

Earthquake Zones Find out where and why earthquakes occur and why there are earthquake zones.

Moment Magnitude Scale Find out why the moment magnitude scale is used to measure great earthquakes.

1964 Alaska Earthquake The Great Alaskan Earthquake find out why Good Friday saved many people's lives!


New Madrid Earthquakes The New Madrid earthquakes were a series of three very large earthquakes felt by people over almost 2 million square miles.

Earthquake Waves Earthquake waves are produced by the more than three million earthquakes each year.

What Causes Earthquakes. Find out what causes earthquakes and other fascinating facts about when our planet shakes, rattles, and rolls.

Kids Fun Science The links on our home page include information about volcanoes, science activities, plate tectonics, the rock cycle and much more.