19.1 & 19.2

f

(t/f) On seismograms, seismic waves recorded from more distance facilities are closer together than those recorded from facilities close to the epicenter.

t

(t/f) P-waves are bent when they strike the core.

t

(t/f) P-waves travel through Earth's mantle.

t

(t/f) S-waves do not travel through Earth's mantle.

t

(t/f) Seismic waves change speed and direction when they encounter different materials.

t

(t/f) Seismologists have reasoned that Earth's outer core must be liquid based on the disappearance of S-waves.

f

(t/f) Studies of how waves reflect deep inside Earth show that Earth's inner core is solid.

f

(t/f) Surface waves are the first to arrive at a seismic facility.

t

(t/f) The P-wave shadow zone does not receive direct P-waves.

seismogram

A paper or computer record of earthquake vibrations.

frame

All seismometers include a _____ suspended from a wire or spring.

mass

All seismometers include a _____ that is anchored to the ground and vibrates during an earthquake.

seismometer

An instrument that records earthquake vibrations.

Elastic

At a lower stress value, _____ deformation occurs.

s & p waves

Can pass through Earth's interior.

s waves

Causes rock to move at right angles to the direction in which the wave travels.

surface waves

Causes rock to move both up and down and from side to side.

strain

Deformation of materials in response to stress.

San Andreas

Famous California strike-slip fault.

fault plane

Fault surface along which movement takes place.

compression

Force that tends to shorten or squeeze something, decreasing its volume.

tension

Force that tends to stretch or elongate something.

fault

Fracture along which movement occurs.

Strike-slip fault

Fracture caused by horizontal shear.

normal fault

Fracture caused by horizontal tension.

reverse fault

Fracture that forms as a result of horizontal compression.

plastic

Rocks at great depths are _________.

brittle

Rocks nears Earth's surface are generally ________.

p waves

Squeezes and pulls rock in the same direction as the wave travels.

plastic deformation

The high stress deformation of a material (failure & _____ limit).

elastic deformation

The low stress deformation of a material (zero & _____ limit).

stress

Total force acting on crustal rocks per unit area.

surface waves

Travels only along Earth's surface.

fails and breaks

When stress exceeds the strength of a material, it...