Chapter 19 science vocabulary

Tsunami

Large powerful ocean wave generated by the vertical motions of the seafood during an earthquake in shallow water can for huge fast moving breakers exceeding 30m in height that can damage coastal areas

Magnitude

Measure of the energy released during an earth quake which can be described using the Richter scale

Modified mercalli scale

Measures earth quakes intensity on a scale of 1 to 7the greater the number the more damage the earth quake caused

Richter scale

Numerical rating system that used to measure the amount of energy that is real eased during an earthquake

Amplitude

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

Seismic wave

The vibrations of the ground during an earthquake

Elastic deformation

Causes material to bend and stretch. Proportional to stress so if stress is reduced or returns to its zero the strain or deformation is reduced or disappears

Strain

Deformation of minerals in response to stress

Stress

Forces per unit area that act on a material compression tension and shear

Fault

Fracture or systems of fractures of earths crust that occurs when stress is applied to quickly or stress is to great can form as a result of horizontal compression ( reverse fault) horizontal shear ( strike slip fault) or horizontal tension ( normal fault)

Seismometer

Instrument used to measure horizontal or vertical motion during a earthquake

Seismic gap

Place along a active fault,that has not experienced a earthquake for a long period of time

Focus

Point of the initial fault strain where an earthquake originates that usually lies at least 7 km beneath earth surface

Epicenter

Point on earths surface above the focus of a earthquake

Plastic deformation

Premanent deformation caused by strain when stress exceeds a certain value

Soil liquefaction

Process associated with seismic vibrations that occur in areas of sand that is nearly saturated resulting in the ground behaving like a liquid

Seismogram

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

Moment magnitude scale

Scale used to measure earth quake magnitude taking into account the size of the fault, rupture the rocks stiffness and amount of movement along the fault using values that can be estimated by the size of several types of seismic waves

Secondary wave

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

Primary wave

Seismic wave that squeezes and pushes rock in the same direction that the wave travels known as a p wave