1. earthquake waves
   1. body waves
      1. p-waves
         1. speed 5 to 7 km/s
         2. formed by alternate expansion and contraction of bedrock
      2. s-waves
         1. slower than p-waves
         2. formed from sheer stress and move the materials they pass through in a vertical or horizontal
   2. surface waves
      1. travel at or near the ground
      2. cause rolling or sweeping motion
      3. velocity is slower than that of body waves
      4. despite slow speed,cause considerable damage to construction as it causes strong ground movement
2. detecting earthquakes
   1. Chinese seismograph
      1. 2000 years ago Chinese studied earthquake waves and to determine the direction
      2. hollow jar,heavy weight in jar suspended,metal balls in each dragon,which when opened falls in the mouth of the frog
   2. modern seismograph
      1. uses heavy weight with a pen on rolls of paper
3. plate boundaries
   1. spreading zones
      1. molten rock rises pushing two plates apart
      2. they are mostly found in oceans
   2. transform faults
      1. plates slide past each other
   3. subduction zones
      1. one plate overrides the other
4. 6000 earthquakes every year
   1. 500 felt
   2. 15 cause damage
   3. 10000 people die every year
5. oldest record of an earthquake from Shang dynasty,Chinese 3000 years ago