Seismicity - Earthquakes

Earthquakes - these are events of violent shaking of the crust caused by a sudden release of pressure.
1. pressure is released in the focus, shock waves have the highest level of energy. Energy dissipates as you move away from the focus.
  1. shallow focus - 0-70km
  2. intermediate - 70-300km
  3. deep - 300-700km
2. The area directly above the focus is the epicentre.
Types of seismic waves
1. P-Waves - fastest, shake backwards/forwards, move through solids and liquids
2. S-Waves - slower, move sideways, shake at right angles, cannot move through liquid, more damaging than p-waves
3. Surface waves - near surface, significantly slower, more destructive
  1. L-waves - long waves - ground moves sideways
  2. Raleigh waves - moves ground up and down
Magnitude - the amount of energy released, usually measured on the Richter scale
1. each unit represents a 10x increase in strength and a 30x increase in energy released
2. intensity is measured by its effects on the Mercalli scale
Frequency - varies between active regions such as Sudan trench and seismic zones within the shield of ancient crust like Greenland.
1. Seismometers measure the shockwaves, it can be used to distinguish patterns.

Resource summary

	Created by Evie Davis over 7 years ago