Waves and the Earth

Waves and the Earth

1. Earthquake Waves

   • S-Waves
   • P-Waves
   • Are detected using seismometer
     • S-Wave arrival time x Speed of S-Wave = Distance of earthquake
     • The position of the Earthquake can be found using 3 or more distances from different seismometers through TRIANGUALTION
   • When these waves travel through the Earth they change direction

2. P-Waves have a very low frequency less than 20Hz

   • The frequency is the number of waves detected every second
     • A frequency of less than 20Hz is called INFRASOUND
     • A frequency of higher than 20 000Hz is called ULTRASOUND
       • Ultrasound is used in medicine
       • Ultrasound is used by animals
       • Ultrasound is used in underwater detection

3. Earthquakes are caused when the crust moves

   • The crust can move at a FAULT
     • This movement can be modelled
   • Tectonic plates move driven by heat convection within the Earth

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