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What is an earthquake?
Earthquakes are the vibrations caused by rocks breaking under stress. The underground surface along which the rock breaks and moves is called a fault plane. A fault plane is the plane that represents the fracture surface of a fault.
How is an earthquake formed?
The Earth’s outer shell, the lithosphere, consisting of the crust and uppermost mantle, is divided into a patchwork of large tectonic plates that move slowly relatively to each other. These tectonic plates are what causes an earthquake to happen. As you can see on the diagram, the crust is the outermost solid shell of Earth. Below the lithosphere is a layer of upper mantle called the asthenosphere. This is made up rock that is fluid and can move. It is this fluidity that powers the movement of the tectonic plates of the Earth's crust. There are 7-8 major plates and many minor plates. The movement of a plate is driven by shifting in the underlying hot and viscous mantle.
What are the different magnitudes of an earthquake?
Magnitude - Earthquake Effects - Estimated number each year
2.5 or less - Usually not felt, but - 900,000
can be recorded by
seismograph.
2.5 to 5.4 - Often felt, but only - 30,000
causes minor damage.
5.5 to 6.0 - Slight damage to - 500
buildings and other
structures.
6.1 to 6.9 - May cause a lot of - 100
damage in very
populated areas.
7.0 to 7.9 - Major earthquake. - 20
Serious damage.
8.0 or greater - Great earthquake. - One every 5 to 10 years
Can totally destroy
communities near the
epicenter.
Earthquakes are the vibrations caused by rocks breaking under stress. The underground surface along which the rock breaks and moves is called a fault plane. A fault plane is the plane that represents the fracture surface of a fault.
How is an earthquake formed?
The Earth’s outer shell, the lithosphere, consisting of the crust and uppermost mantle, is divided into a patchwork of large tectonic plates that move slowly relatively to each other. These tectonic plates are what causes an earthquake to happen. As you can see on the diagram, the crust is the outermost solid shell of Earth. Below the lithosphere is a layer of upper mantle called the asthenosphere. This is made up rock that is fluid and can move. It is this fluidity that powers the movement of the tectonic plates of the Earth's crust. There are 7-8 major plates and many minor plates. The movement of a plate is driven by shifting in the underlying hot and viscous mantle.
What are the different magnitudes of an earthquake?
Magnitude - Earthquake Effects - Estimated number each year
2.5 or less - Usually not felt, but - 900,000
can be recorded by
seismograph.
2.5 to 5.4 - Often felt, but only - 30,000
causes minor damage.
5.5 to 6.0 - Slight damage to - 500
buildings and other
structures.
6.1 to 6.9 - May cause a lot of - 100
damage in very
populated areas.
7.0 to 7.9 - Major earthquake. - 20
Serious damage.
8.0 or greater - Great earthquake. - One every 5 to 10 years
Can totally destroy
communities near the
epicenter.
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