Unit 1.7

• P waves

  Primary waves, fastest, arrive first
• S waves

  Secondary waves, slower, arrive second
• Surface waves

  Slowest, arrive last, travel along the Earth's surface only
• Following an earthquake, three different types of seismic waves are created: P waves, S waves, and surface waves
• P waves can travel through solid and liquid rock, S waves can only travel through solid rock, and surface waves can only travel along the Earth's surface</b>
• An earthquake at X will create all three types of seismic waves which can be measured across the Earth
• As only P waves reach the opposite side of the Earth from X, the outer core must be liquid as S waves cannot travel through it
• Lag time

  The delay between P waves and S waves arriving, can be used to calculate the distance to the earthquake
• Using lag time data

  1. Convert lag time into a distance

  2. Draw circles with a radius equivalent to that distance

  3. Find the point where the circles meet, this is where the earthquake happened
• P waves are faster than S waves and following an earthquake will arrive first
• Lag time

  Furthest from the earthquake = longer lag time, Closest to the earthquake = shorter lag time
• The delay between P waves and S waves arriving is known as the lag time and can be used to calculate the distance to the earthquake from that point
• Using data from three stations, you can convert the lag time into a distance and draw circles with a radius equivalent to that distance to find the point where the circles meet, which is where the earthquake happened
• The outer core must be liquid as S waves cannot travel through it
• P waves can travel through the liquid outer core, but S waves cannot
• P and S waves can travel through the solid mantle
• Surface waves travel on the surface of the Earth, not into the mantle