seismic waves

• what produces seismic waves?

  earthquakes
• what are earthquakes caused by?

  the sudden release of energy along the faults in the Earth's crust, resulting in tectonic plates colliding with, sliding past or moving away from each other and the ground vibrating
• seismic waves travel out though the...

  Earth
• how are seismic waves detected?

  by using seismometers over the surface of the planet
• seismometers


  devices that measure the amount of ground motion (magnitude) caused by an earthquake; also called seismographs
• what happens when seismic waves reach a boundary between the different layers of the Earth?

  some waves will be absorbed and some will be refracted
• seismic waves refract/get absorbed at different layers of the Earth because...

  the layers have different properties (such as density)
• what happens if the seismic waves are refracted?

  they change speed gradually, resulting in a curved path
• how do seismic waves provide evidence for the Earth's structure?

  because scientists were able to observe where seismic waves were absorbed/refracted and came to the conclusion that the Earth had layers (which had different densities and thicknesses)
• Earth's structure diagram

  
• what are the two different types of seismic waves?

  P waves and S waves
• what does P wave stand for?

  primary wave
• P waves are...


  longitudinal
• P waves travel through...

  solids and liquids
• P waves travel ... than S waves

  faster
• P waves are able to travel though...

  Earth's core
• P wave diagram

  
• what does S wave stand for?

  secondary wave
• S waves are...


  transverse
• S waves travel through...


  solids only
• S waves are ... than P waves

  slower
• S waves are unable to travel through...

  Earth's core
• S wave diagram

  
• why are there some parts of Earth which do not receive shock waves at all?

  molten areas within the Earth slow down P waves and stop S waves because their shearing motion cannot be transmitted through a liquid
• which area of Earth experiences the most earthquakes and why

  the pacific ocean; it is the most seismically active zone in the world because it is where several tectonic plates meet