Chapter 8Sections 1-4

By:Kelsey GarrisonBrittany Ramsey

Seismology• The study of earthquakes. The

scientists who study the earthquakes are called seismologists.

Fault• A break in the Earth’s crust along

which blocks of the crust slide relative to one another. Earthquakes occur along faults due to this sliding.

Deformation • The change in the shape of a rock in

response to stress. • Rock along a fault deforms mainly in two

ways-in a plastic manner, like a piece of molded clay, or in a n elastic manner, like a rubber band.

Elastic rebound• The sudden return of elastically

deformed rock to its original shape. • Elastic rebound occurs when more

stress is applied to rock than the rock can withstand.

Seismic waves• Waves of energy that travel through the

earth.• Different types of seismic waves travel at

different speeds and move the materials that they travel through differently.

P waves• Travel through solids, liquids, and

gases-fastest seismic waves. Because p waves are always the first seismic waves to be detected, they are also called primary waves.

S waves• Shear waves-second fastest seismic

wave. Also, S waves are slower than P waves and always arrive second; thus, they are also called secondary waves.

Seismographs• Are instruments located at or near

the surface of the earth that record seismic waves.

Seismogram• A tracing of earthquake motion

created by a seismograph. • Seismologists use seismograms

to calculate when an earthquake started.

Epicenter• Thon the Earth’s e point surface directly above an

earthquakes starting point. • The most common method by which

seismologists find an earthquake’s epicenter is the

Focus• The point inside the Earth where

an earthquake begins.

Gap hypothesis• States that sections of active faults

that have had relatively few earthquakes are likely to be the sites of strong earthquakes in the future.

Seismic gaps• The areas along a fault where relatively

few earthquakes have occurred.

Moho• A place within the Earth

where the speed of seismic waves increases sharply. It marks the boundary between the Earth’s crust and mantle.

Shadow zone• An area on the Earth’s surface where no direct seismic waves from a particular earthquakes can be detected.