Seismicity: The Causes of Earthquakes
Refers to AQA A2 Geography
Plate Tectonics and Assosiated Hazards Option
- Created by: Bethany
- Created on: 29-04-14 17:58
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- The Causes of Earthquakes
- The Process
- The crust if the earth us mobile so there is a build-up of stress within the rocks
- Pressure is suddenly released
- Causes parts of the earth's surface to experience intense shaking motion which lasts for a few seconds.
- Pressure is suddenly released
- The crust if the earth us mobile so there is a build-up of stress within the rocks
- The Focus and Epicentre
- The point at which the pressure release occurs within the crust is known as the FOCUS
- The point on the earth's surface immediately above the focus is known as the EPICENTRE (where the earthquake is felt)
- The depth of the FOCUS is significant...
- SHALLOW FOCUS (0-70km deep)
- Tend to cause the greatest damage and account for 75% of all earthquake energy released
- INTERMEDIATE FOCUS (70-300km deep)
- DEEP FOCUS (300-700km deep)
- SHALLOW FOCUS (0-70km deep)
- Pressure is suddenly released
- Causes parts of the earth's surface to experience intense shaking motion which lasts for a few seconds.
- The point at which the pressure release occurs within the crust is known as the FOCUS
- Seismic Waves
- Radiate from the focus like ripples in water when a stone is thrown into a pond
- There are three types of seismic waves...
- PRIMARY (P) WAVES
- Travel fastest and are compressional, vibrating in the direction of travel
- SURFACE (L) WAVES
- Travel slowest and near to the ground surface.
- Some surface waves shake the ground at right angles to the direction of wave movement and sometimes have a rolling motion producing vertical ground movement.
- SECONDARY (S) WAVES
- Travel at half the speed of P Waves and shear rock by vibrating the direction of travel,
- PRIMARY (P) WAVES
- There are three types of seismic waves...
- Radiate from the focus like ripples in water when a stone is thrown into a pond
- The Process
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