Chapter 19

Tsunami

A large ocean wave generated by vertical motions of the sea floor during an earthquake

Moment Magnitude Scale

A rating scale that measures the energy released by an earthquake

Fault

Any fracture or system of fractures along which Earth moves

Soil Liquefaction

Areas with sand that is nearly saturated with water, seismic vibrations can cause the ground to behave like a liquid

Elastic Deformation

Caused when a material is compressed, bent, or stretched

Richter Scale

Devised by a geologist named Charles Richter, is a numerical rating system that measures the energy of the largest seismic waves

Seismometers

Instrument used to measure horizontal or vertical motion during an earthquake

Magnitude

Measure of the energy released during an earthquake, which can be described using the Richter scale

Modified Mercalli Scale

Rates the types of damage and other effects of an earthquake as noted by observers during and after it's occurrence

Seismogram

Record produced by a seismometer that can provide individual tracking of each type of seismic wave

Seismic Gaps

Sections located along faults that are known to be active, but which have not experienced significant earthquakes for a long period of time

Secondary Waves

Seismic wave that causes rock particles to move at right angles to the direction of the wave, known as an S-wave

Primary Waves

Squeeze and push rocks in the direction along which the waves are traveling

Strain

The deformation of materials in response to stress

Epicenter

The point on Earth's surface directly above the focus

Focus

The point where the waves originate

Amplitude

The size of the seismic waves; an increase of 1 in the scale represents an increase in amplitude of a factor of 10

Stress

The total force acting on crustal rocks per unit area

Seismic Waves

The vibrations of ground produced during an Earthquake

Plastic Deformation

When stress builds up past a certain point, called the elastic limit