.:Earthquake:.

Formation of Earthquakes

• Earthquakes form when there is a vibration in the earth’s crust, causing a sudden release of energy. This energy is radiated out from the quake’s epicenter, in the form of seismic waves.

• There are two types of seismic waves, the P-waves, or primary waves and the S-waves, also known as secondary waves. The P-Waves are the first waves to arrive during an earthquake. They compress and dilate (push together and pull apart) rocks in the ground, and they can travel through solids and liquids. The S-waves arrive after the P-waves. They move more slowly than the P-waves.As they pass through the ground they cause the rocks to move from side to side.

Major Earthquake zones

• Locations of earthquakes are closely related to plate boundaries.

• Pacific Ring of Fire

• Mediterranean: Alpine Himalaya-Asia Minor Region

The most common causes of Earthquakes are faults. There are a few different kinds of faults. This energy comes about when two tectonic plates rub against each other.

Normal Faults

Formed when rocks are pulled apart, when the rock strata is under tension. Caused by forces acting in opposite directions. This results in a block of land moving down relative to the other block, and this forms an escarpment. Normally, normal faults create long cliffs.

Reverse Faults

Formed when rock strata are pushed together, causing one side to ride over the other. One block of land moves up against the direction of the fault. This creates an overhanging scarp, which soon collapses due to gravity and weathering. Eventually, it produces a gentle slope.

Tear Faults

Also known as a strike-slip fault. They are formed when plates slide past each other horizontally. These can be a result of both tensional and compressional forces acting on the strata.