19.1 Earthquakes
elastic deformation
causes material to bend and stretch
fault
fracture or system of fractures in earths crust that occurs when stress is applied too quickly, or stress is too great
plastic deformation
permanent deformation caused by strain when stress exceeds a certain value
epicenter
point on earths
strain
the deformation of materials in response to stress
focus
the point of initial fault rupture where an earthquake originates that usually lies at least several kilometers beneath earths surface
secondary wave
the seismic wave that causes rock particles to move at right angles to the direction of the waves
primary wave
the seismic wave that squeezes and pushes rocks in the came direction that the wave travels
stress
the total force is acting on crustal rocks per unit of area.
seismic wave
the vibrations of the ground during an earthquake