infrasound + seismic waves

• what are infrasound waves?

  sound waves that are so low in frequency that we can't hear them - under 20Hz
• which animals communicate using infrasound?

  elephants and whales
• which natural events produce infrasound in the local area?

  volcanoes, avalanches, earthquakes
• what is used to detect seismic waves?

  seismometers
• what will happen when seismic waves reach a boundary between different layers of material?

  inside the Earth, some waves will be absorbed and some will be refracted
• what happens if the seismic waves are refracted?

  they change speed gradually, resulting in a curved path
• what happens if the properties of a seismic waves change suddenly?

  the wave speed changes abruptly, and the path has a kink
• what media do P-waves travel through?

  solids and liquids, they are faster than S-waves
• what media do S-waves travel through?

  solids, they are slower than P-waves