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Earthquakes
• Aims
• To know where earthquakes occur
• To know how earthquakes occur
• To be able to give examples of
earthquakes
• To know about the characteristics of
earthquakes in different parts of the world
Fault
• a fracture in the rocks of the Earth’s crust,
where compressional or tensional forces
cause relative movement of the rocks on
the opposite sides of the fracture.
• Can be a few centimetres to many
hundreds of kilometres long
Describe the distribution of earthquakes
Map of plate boundaries
• https://www.youtube.com/watch?v=e7ho6
z32yyo
Earthquake depth
• Earthquakes can occur anywhere between
the Earth's surface and about 700
kilometers below the surface.
• Shallow earthquakes are between 0 and
70 km deep; intermediate earthquakes, 70
- 300 km deep; and deep earthquakes,
300 - 700 km deep.
• Deep focus earthquakes tend to be along
island arcs and subduction zones (around
the Benioff zone) Why is this odd?????
How do earthquakes occur?
Plates become stuck and stop moving
Pressure builds up underneath the
crust
Eventually the pressure becomes too
much and the plates move with a jolt
This is an earthquake
Exceptions
• Mines
• Reservoirs
• Old fault lines e.g. Market Raesen 2008
5.2 on the Richter Scale
How do earthquakes occur?
1. General
explanation
Collision
DestructiveConstructive
Conservative Other
Seismicity
Explain how earthquakes
occur on each plate
margin. Add in examples
with dates and Richter
Scale Readings.
P and S waves •P waves travel through solids and liquids
•They travel very fast (nearly twice the speed of
S waves – 300m/s through air, 5000m/s through
granite
•They push and pull and can compress
•S waves can travel through solids but not
liquids.
•They vibrate from side to side
•They travel more slowly than P waves – about
60% slower
•The side to side movement causes the most
damage to buildings as a result of the shearing
effect.
•The lack of S waves and the slowness of P
waves was used to discover that the outer core
is liquid
https://www.youtube.com/w
atch?v=gFU3_mZdGfY
Discuss why surface
waves (Love and
Rayleigh) are the most
damaging.
Earthquakes
• Aims
• To know where earthquakes occur
• To know how earthquakes occur
• To be able to give examples of
earthquakes
• To know about the characteristics of
earthquakes in different parts of the world