Seismic waves

Question 1

When are seismic waves transmitted?

Answer 1

• When large scale events occur (earthquakes, volcanoes and explosions), seismic waves are sent out in all directions and pass through the different layers of the Earth

Question 2

Explain seismic P - waves

Answer 2

• Longitudinal
• Can travel through solids and liquids
• Much faster than S - waves

Question 3

Explain seismic S - waves

Answer 3

• Transverse
• Can only travel through liquids
• Slower than P - waves

Question 4

How do seismologists use seismic waves

Answer 4

• When a large scale event occurs, seismologists record the waves using a seismometer
• They then compare how long it took the wave to go from the site of the event to different places around the Earth
• This helps them gain an understanding of the internal structure of the Earth

Question 5

How do seismic P - waves pass through the Earth?

Answer 5

• When P - waves reach a boundary between two mediums, they are either reflected, absobed or refracted
• As the different layers of the Earth aren’t all the same density (the mantle isn’t always the same density), the waves will always be being gently refracted (changing direction)
• The refraction is more obvious at a boundary

Question 6

How do seismic S - waves pass through the Earth?

Answer 6

• They can’t pass through the liquid outer core (can’t pass through liquids)
• This is how scientists were able to discover the liquid outer core (as only P - waves were recorded on the opposite side of the Earth to the event, not S - waves)