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Science Vocab

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fault
Surface along which rocks move when they pass their elastic limit and break.
earthquake
Vibrations produced when rocks break along a fault.
normal Fault
Break in rock caused by tension forces, whrer rock above the fault surface moves down relative to the rock below the fault surface.
reverse fault
Break in rock caused by compressive forces, where rock above the fault surface moves upward relative to the rock below the fault surface.
strike-strip fault
Break in rock caused by shear forces, where rocks move past each other without much vertical movement.
seismic wave
wave generated by an earthquake.
focus
In an earthquake, the point below Earth's surface where energy is released in the form of seismic waves.
primary wave
Seismic wave that moves rock particles back-and-forth in the same direction that the wave travels.
secondary wave
seismic wave that moves rock particles at right angles to the direction of the wave.
surface wave
Seismic wave that moves rock particles up-and-down in a backward rolling motion and side-to-side in a swaying motion.
epicenter
Point on Earth's surface directly above an earthquake's focus.
seismograph
instrument used to register earthquake waves and record the time that each arrived
magnitude
measure of the energy released during an earthquake
liquefaction
occurs when wet soil acts more like a liquid during an earthquake
tsunamis
Seismic sea wave that begins over an earthquake focus and can be highly destructive when it crashes on shore