Earthquake Waves
“Seismic” always has to do with earthquake activity Seismic Waves As the rock layers are shaking back and forth they send out waves of vibration called Seismic Waves “Seismic” always has to do with earthquake activity
Epicenter Fault Focus Seismic Waves
Seismic Waves are waves of vibration sent out in all directions from the FOCUS (point of the discharge of energy from rock fracture)
Focus The point below the surface where the rock layers break and move Epicenter The point on the surface, directly above the focus. Where the greatest damage usually occurs
Types of Seismic Waves
Body Waves are waves that travel through the body of the earth Surface waves only travel along the surface of earth
2 types: P waves and S waves Body Waves 2 types: P waves and S waves
Primary Waves AKA P-Wave Type of Longitudinal Wave Causes back and forth motion Follows the same direction as the energy transfer
P-Waves Type of COMPRESSIONAL wave- means they move through (compress) a solid or liquid by pushing or pulling similar to the way sound travels through the air Will travel through solid, liquid or gas Travels at: 7.8 – 8.5 kps in mantle 7.2 kps in oceanic crust 3.5 kps in continental crust
The particles of the material a P Wave pushes through move in the direction of the P wave's energy. This is called the direction of wave propagation. http://sunshine.chpc.utah.edu/labs/seismic/surface.swf
Primary or “P” Wave
Secondary Wave-AKA S-Wave The 2nd wave to Move out from the earthquake focus Move slower than primary waves Movement: Move at right angles to primary waves causing rocks to move up and down and side to side … this is known as a (transverse wave) A type of seismic wave that moves the ground up and down or side to side
Secondary Wave AKA S-Wave Particle motion is perpendicular to direction of energy transfer Transverse or Shear Wave Will travel only through solids (solid rock) Travels 4 – 5 kps
Secondary Wave http://sunshine.chpc.utah.edu/labs/seismic/surface.swf
Secondary or “S” Wave
Comparing Seismic Waves
Surface Waves
Two main types of surface waves: Love Wave Rayleigh Wave
Love Wave http://sunshine.chpc.utah.edu/labs/seismic/surface.swf
Love Waves Love Waves travel less than 4 kps Move side-to-side; like a snake Cause the most damage
Seismic Waves
Seismogram with the P-Wave, S-Wave and L-Wave
Seismic Risk in the US
Triangulation