Earthquakes
Science: KS3, topic 3.3.5
Earthquakes
We can feel earthquakes - but did you know they send out waves as well? Earthquakes produce two types of waves: primary and secondary waves.
Earthquakes
- Earthquakes are due to a rise in pressure in the Earth's crust.
- Earthquakes occur along tectonic plate boundaries.
Focus and epicentre
- The focus is where the earthquake originates from.
- The epicentre is the point on the surface of Earth directly above the focus.
Measuring earthquakes
- Earthquakes send out seismic waves from the focus (S and P waves).
- The strength of the earthquake is measured on the Richter Scale.
- A seismograph measures the seismic waves.
Primary waves
- Primary or P waves are longitudinal.
- Primary waves travel through liquids and solids.
- Primary waves travel through the Earth's liquid core.
- So primary waves can be detected worldwide.
Primary wave detection
- Primary waves travel faster than S waves.
- So primary waves are first to be detected on a seismograph.
Secondary waves
- Secondary or S waves are transverse.
- Secondary waves can only travel through solids.
- Secondary waves shake the ground.
- Secondary waves are seismic waves.
Test yourself on Earthquakes
What is used to measure the strength of an earthquake?
Which of these are true of earthquakes?
Which earthquake wave shakes the earth?
Which is true of P waves and seismographs?
Which of these are true of S-waves?