A normal fault develops where land is pulling apart due to tectonic plate movement. The rocks fracture and one side of the fault drops down in a normal fault.
Fault going through wall at Burgh Castle USGS
Focus and epicenter of an earthquake
Pressure inside the Earth forces rocks to break forming cracks in the Earth's crust. These cracks are faults. The earthquake focus is the place where the rocks break along the fault plane. The earthquake epicenter is the point directly above the earthquake focus on the Earth's surface.
Fault block movement
Faults form when one section of the land moves downward because tectonic forces are pulling the land apart. Blocks of land usually move downward in a steeply inclined plane. These faults will have a hanging wall and a footwall.
The hanging wall moves downward in relation to the footwall. These terms came into use by miners when they found minerals at the base of cliffs formed by inactive faults.
Every time there is movement along the fault plane there are P waves and S waves. P waves and S waves are produced by all earthquakes large or small. Large earthquakes along faults can also produce Love waves and Rayleigh waves. These are the most destructive waves and only travel on the Earth's surface.
1964 Alaska Earthquake The 1964 Alaska quake was the largest earthquake ever recorded in North America.
Richter Magnitude Scale The Richter magnitude scale was developed in 1935 to study California earthquakes.
Moment Magnitude Scale The moment magnitude scale measures the total energy released by great earthquakes.
Normal Fault Find out how and why normal faults form.
Earthquake Waves Find out which earthquake waves are produced only by large earthquakes.
Earthquake Facts Did you know that an earthquake can occur any place on Earth?
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