Physical Geology Test 4 Chapter 14

Front 1

Earthquake

Back 1

the vibration of the Earth produced by the rapid release of energy.

Front 2

Focus

Back 2

This is the point within the Earth where rock displacement generates the release of energy

Front 3

Faults

Back 3

large fractures in the Earth’s crust caused by the rock displacements that produces earthquakes
These can move either vertical or horizontal.

Front 4

Elastic Rebound

Back 4

These are the vibrations we feel on Earth caused by underlying rock returning to its original shape.

Front 5

Aftershock

Back 5

These are the smaller earthquakes that form as part of one of the adjustments that occur after a major earthquake.

Front 6

Foreshock

Back 6

These are the small earthquakes that precede a major earthquake by days or even years.
Monitoring foreshocks is currently being done to attempt to predict the coming of a major earthquake.

Front 7

Fault Creep

Back 7

These are the portions that exhibit a slow, gradual displacement. These occur relatively smoothly and with little noticeable seismic activity.

Front 8

Stick-slip motion

Back 8

This is the process in which some portions store energy (after displacement) for long periods of time before rupturing, resulting in great earthquakes.

Front 9

Seismology

Back 9

The study of Earthquakes

Front 10

Seismographs

Back 10

The instruments that record earthquakes.

Front 11

Seismograms

Back 11

The actual records (paper or digital) of earthquakes.
These indicate two types of seismic waves, Surface waves and Body waves

Front 12

Epicenter

Back 12

The location on the surface directly above the focus.
 Difference n velocities of P and S waves allow us to determine the location of the epicenter…the greater the interval between their arrivals, the greater the distance to the earthquake source.

Front 13

Triangulation

Back 13

The process of locating an earthquake using three or more seismic stations to record an earthquake, and then drawing circles to corresponding distances to the earthquake around each station. The intersection of those circles will indicate the location of the epicenter.

Front 14

Liquiefaction

Back 14

The process by which sediment that is very wet starts to behave like a liquid. Liquefaction occurs because of the increased pore pressure and reduced effective stress between solid particles generated by the presence of liquid. It is often caused by severe shaking, especially that associated with earthquakes.

Front 15

Seismic wave/tsunami

Back 15

rapidly moving ocean wave generated by earthquake activity and capable of inflicting heavy damage in coastal regions.

Front 16

Surface Waves

Back 16

Surface waves: Waves that travel along the Earth’s outer layer.
These motions are up and down and side to side
The side to side motion is very damaging to building foundations

Front 17

Body Waves

Back 17

Body waves: Waves that travel through the Earth’s interior.
Two Types, Primary Waves (P-Waves) and Secondary Waves (S-Waves)

Front 18

P Waves

Back 18

These push (compress) and pull (expand) rocks in the direction they are traveling
Solids, liquids, and gases resist changes in volume…therefore they will spring back when the force is removed
P-waves travel through solids, liquids, and gases
P-waves are also known as Compressional Waves.

Front 19

S Waves

Back 19

S-waves “shake” the materials it travels through at right angles to their direction of travel
S-waves don’t change the volume of material they pass through like P-waves but instead change the shape of the material they pass through
Gases and liquids don’t elastically respond to changes in shape…therefore S-waves don’t travel through liquid or gases.

Front 20

Moho

Back 20

The boundary separating the crust and the mantle, discernible by an increase in seismic velocity.
Founded in 1909 when Andrija Mohorovicic found that seismic waves increase velocity abruptly ~50 kilometers beneath the Earth’s surface…and that boundary separates the crust from the underlying mantle and thus termed it Mohorovic discontinuity or Moho.

Front 21

P-wave Shadow Zone

Back 21

The zone which P waves are absent (from 105 degrees to 140 degrees around the globe of an earthquake).
In this zone, rather than stopping all P-waves, these waves are actually bent or refracted, thus explaining the lapse in expected arrival times.
This shadow zone could be explained if Earth contained a core composed of material unlike the overlying mantle.

Front 22

S-Wave Shadow Zone

Back 22

It was also learned that S waves do not travel through the core…all of this information was evaluated and it was determined that Earth’s core contained a portion that was liquid.

Front 23

Shadow Zone

Back 23

The zone between 105 and 140 degrees distance from an earthquake epicenter that direct waves do not penetrate because of the refraction by Earth’s core.