Earthquake Vocabulary

Fault surface along which rocks move when they pass their elastic limit

surface along which rocks move when they pass their elastic limit

Earthquake vibrations produced when rocks break along a fault

vibrations produced when rocks break along a fault

Normal Fault break in rock caused by tension forces, where rock above the fault surface moves down relative to the rock below the fault surface

break in rock caused by tension forces, where 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

break in rock caused by compressive forces, where rock above the fault surface moves upward relative to the rock below the fault surface

Strike-Slip Fault break in rock caused by shear forces, where rocks moves past each other without much vertical movement

break in rock caused by shear forces, where rocks moves past each other without much vertical movement

Focus The point below the Earth’s surface where energy is released in the form of seismic waves

The point below the Earth’s surface where energy is released in the form of seismic waves

Seismic Wave wave generated by an earthquake

wave generated by an earthquake

Primary Wave (P-Wave) seismic wave that moves rock particles back and forth in the same direction that the wave travels. These waves travel fastest and arrive first.

seismic wave that moves rock particles back and forth in the same direction that the wave travels. These waves travel fastest and arrive first.

P- Wave

Secondary Wave (S-Wave) seismic wave that moves rock particles at right angles to the direction of the wave. These waves arrive second.

seismic wave that moves rock particles at right angles to the direction of the wave. These waves arrive second.

S- Wave

Comparison P-Wave S-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. These waves arrive last and are the most destructive.

Seismic wave that moves rock particles up and down in a backward rolling motion and side to side in a swaying motion. These waves arrive last and are the most destructive.

Damage Video

Epicenter point on Earth’s surface directly above an earthquake’s focus

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

Instrument used to register earthquake waves and record the time that each arrived

Magnitude The power of an earthquake. Measured by the Richter Scale (1-10)

The power of an earthquake. Measured by the Richter Scale (1-10)