Seismic
Waves
Seismic Waves
• Transport the energy given off by
earthquakes
• Travel through the earth in all
directions
• Change speed and directions as they
move from one layer of the earth to the
next due to density differences
P Waves
P Waves (Primary Waves)
•Compressional waves
•Travel through all types of materials
•Cause rock material to vibrate back
and forth parallel to the direction of
wave motion
•8 km/s
P Wave Animation
S Waves
S Waves (Secondary Waves)
S Wave
Animation
• Shear Waves
• Can only travel through solids
• Causes particles to move at right angles
to the wave motion
• 4 km/s
Comparing P and S waves
Surface Waves
• Complex motion. Upand-down and sideto-side.
• Slowest.
• Causes damage to
structures during an
earthquake.
Types of surface
waves = Love waves
(L-waves) and
Rayleigh waves
What is an aftershock?
• Earthquakes usually come in clusters
divided into foreshocks, mainshocks and
aftershocks
• Aftershocks must occur geographically
near the mainshock, though they can
occur on another nearby fault, triggered
by the stress on the mainshock's fault.