Waves in the Earth

• Waves get refracted and reflected across Boundries between rocks/layers with different properties
• Velocity increases with depth meaning lines on a traveltime curve should be curved
• FAST


  waves going into something Faster move Away from the normal

  Waves going into something Slower move Towards the normal
• S Waves cannot travel in liquids, however P Waves slow down and refract towards the normal
• From 142’ to 103’ P waves cannot be found
• From -103’ to 103’ S waves cannot be found
• For closer geophones, the shorter, direct path takes less time. For the geophones further away, the longer but faster refracted path is quicker and reaches the geophones before the direct path
• Moho

  The boundary between 25km and 60km deep beneath the continents and between 5km and 8km beneath the ocean floor
• Waves travel faster in the mantle due to a higher incompressibility and more rigidity
• Due to waves arriving quicker than predicted scientists came up with the idea that there must be a boundry