RG 19.1 Forces Within Earth
Epicenter
The point on Earth's surface directly above the focus.
Secondary Waves
are named with respect to their arrival times.
Elastic Deformation
caused when a material is compressed, bent, or stretched.
Fault
is any fracture or system of fractures along which Earth moves.
Plastic Deformation
when stress builds up past a certain point, called the elastic limit, rocks undergo.
Focus
the point of failure where the waves originate.
Stress
the total force acting on crustal rocks per unit of area.
Seismic Waves
the vibrations of the ground produced during an earthquake.
Primary Waves
squeeze and push rocks in the direction along which the waves are traveling.
Strain
deformation of materials in response to stress.