Earthquakes
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What is an earthquake?
The shaking and vibration of the Earth’s crust.
What causes earthquakes to occur?
When tension is released from the crust.
What is the point where pressure is released called?
The focus
What is the point on the Earth’s surface above the focus called?
The epicentre
What is earthquake energy released in?
Seismic waves
Describe what happens as the seismic waves travel away from the epicentre.
They get weaker, seismic waves are felt most strongly at the epicentre. The most severe earthquake damage will occur at the epicentre.
What is a wave?
A vibration that transfers energy from one place to another without transferring matter.
What are the two types of seismic waves and how are they different?
P-waves and S-waves. They are different in the way that they travel through the Earth.
Describe the detection differences between the two types of seismic waves.
Both types of waves can be detected near the earthquake centre but only P-waves can be detected on the other side of the Earth.
What can P-waves travel through?
Solids and liquids
What can S-waves travel through?
Solids
Why can’t S-waves travel through the Earth?
Because liquid layers inside the Earth block its travel.
Describe P-waves
P stands for primary because they arrive at the detector first. They are longitudinal waves which mean the vibrations are along the same direction as the direction of travel.
Describe S-waves
S stands for secondary because they arrive at the detector second. They are transverse waves which means the vibrations are at right angle to the direction of travel.
How are surface waves generated?
When the source of the earthquake is close to the Earth’s surface.
Describe the speed and destructiveness of surface waves in comparison to S-waves
They are slower than S-waves but more destructive.
What are the two types of S-waves?
Rayleigh waves Love waves
Describe Rayleigh waves
Travel as ripples similar to those on the surface of water.
Describe Love waves
Cause horizontal shearing of the ground and they usually travel slightly faster than Rayleigh waves.
What machine measures the power of an earthquake?
A seismometer.
What does a seismometer do?
A seismometer detects the vibrations caused by an earthquake and it plots these vibrations on a seismograph.
Elaborate on the strength of an earthquake and how it is measured.
The magnitude of an earthquake is measured using the Richter scale which is numbered 0-10.