Ch. 2 Sec. 2 Earthquakes & Seismic Waves

•shaking & trembling that results from movement of rock beneath Earth’s surface

TLC-Make a quake

Focus-area beneath Earth’s surface where rock under stress breaks

Epicenter-point on surface directly above focus

seismic wavesseismic waves

• vibrations that travel thru Earth carrying energy released during earthquake

• carry energy from earthquake away from focus Earth’s interior across surface

types of seismic waves

types of seismic waves

P wavesP waves S wavesS wavessurface waves

surface waves

P waves• Primary waves• 1st to arrive• move thru. solids

& liquids• compress &

expand like accordion

S waves• Secondary waves• 2nd to arrive• vibrate from side to

side & up & down• cannot move thru.

liquids

surface waves• move slower than P & S waves

• produce the most severe ground movements

3 types of seismic waves

3 ways ofmeasuring

earthquakes

Mercalli scale

Richter scale

momentmagnitude

scale

rates earthquakesaccording to

level of damage

rated usingseismographs

estimates total energy

released byearthquake

rates earthquakesof all sizes (near & far)

good for small, nearby earthquakes

describes how earthquakes affect

people, bldg. & land

The Mercalli scale was developed to rate earthquakes according to the

amount of damage at a given place.

Earthquake Intensity

Earthquake Effects

I-III People notice vibrations like those from a passing truck. Unstable objects disturbed.

IV-VI Dishes and windows rattle. Books knocked off shelves. Slight damage. People run outdoors.

VII-IX Moderate to heavy damage. Buildings jolted off foundations or destroyed.

X-XII Great destruction. Cracks appear in ground and landslides occur. Waves seen on ground surface.

Mercalli Scale

magnitude•# geologists assign to earthquake based on earthquake’s size

•how much energy released

• instrument that records & measures ground movements of seismic waves

seismograph

seismograph

1.use seismic waves

2.measure difference between arrival times of P & S waves using data from 3 seismographs

3.draw 3 circles from different seismographs

4. point where they intersect= epicenter

A Vocabulary Review Activity

Directions:• One student stands with their back

to this presentation.

• Another student gives the student clues to the vocabulary word onscreen as a clock keeps time.

• The student tries to guess the word before the buzzer.

Ready to play?

earthquake

The is…

magnitude

The is…

Richter scale

The is…

epicenter

The is…

seismograph

The is…

Mercalli scale

The is…

P waves

The is…

S waves

The is…

Surface waves

The is…

focus

The is…

GREAT JOB!

In your drawing, be sure to include:

• A drawing of your building

• List of materials

Walls- styrofoam

Roof- graham crackers