Describe and explain the characteristics of earthquakes (8)

Describe and explain the characteristics of earthquakes (8)

Earthquakes occur when a build-up of pressure within the Earth's crust is suddenly released and the ground starts shaking violently. The point within the crust, at the lithosphere, where pressure is released is called the focus. The focus in an earthquake, can be found at a range of depths, at a shallow focus, which is 0-70km deep, at an intermediate focus which is 70-300km deep and at a deep focus, at 300-700km deep. The focus is not necessarily at a single point- it could be along a fault line. It is near the focus, where waves are stronger and cause more damage, as that is where there is the highest level of energy. 

The place at the Earth's surface immediately above the focus is called the epicentre, it is where the earthquake is felt first. It receives the highest amount of energy and so is the most potentially hazardous location.

From the focus, there are seismic waves which travel out. There are three main types: Primary (P) waves, which are the fastest, are those that can travel through solids and liquids, they can travel through the mantle and the core. The waves push and pull the earth in the same direction as the wave is travelling. Secondary (S) waves can also travel through solids, but not through liquids- so they can travel through the mantle but not the core, so they cannot be measured at a point opposite the focus or epicentre. They move the earth at 90 degrees (at a right angle) to the direction of travel. They do a lot more damage than P waves due to their shearing effect. Surface waves travel the slowest, but cause the most damage. They are further split into surface love (L) waves- which are the slowest waves and cause most damage or Rayleigh waves, which radiate from the epicentre in low-frequency rolling motions.

Comments: 8/8 well done. Some sort of conclusion would help, if time permits.