Download Earthquakes!!! - Learn District 196

Earthquakes!!!
Slide 1
How and Where Earthquakes Occur
Earthquake- the shaking of the Earth’s
crust caused by the release of energy
 Earthquakes can be caused by volcanic
eruption, collapse of a caldera, or even
the impact of a meteor.
 Most earthquakes occur along faults .( A
fault is a break in the lithosphere along
which movement has occurred)

Slide 2
Friction

Friction makes it difficult for the plates

Tension/pressure builds until it the
to move smoothly
forces become too much and rapid
movement occurs (earthquake)
 Following the earthquake, the plates may
return to their original form and shape,
but the damage is already done on the
surface.
 This is called elastic rebound theory.
Slide 3
Movement first occurs at the focus of the
earthquake
 The focus is well below the surface
 The epicenter of the earthquake is the
place on the surface of the Earth directly
above the focus.

Slide 4
The depth of an earthquake depends
upon the type of plate boundary involved
 Energy waves that travel through the
Earth are called body waves.

Slide 5
P waves (primary waves) squeeze and
stretch rock materials. P waves can
travel though any material.
 S waves (secondary or shear waves)
cause rock material to move at right
angles to the direction the wave is
traveling.
 S waves can travel through solids, but
not through liquids and gases.

Slide 6

Surface waves travel along the Earth’s
surface and can produce Love and
Rayleigh waves
Slide 7
Locating and Measuring Earthquakes
A seismograph detects and records
waves produced by earthquakes
 A seismogram is a recording sheet that
shows an earthquake in graphic form

Slide 8

3 recording stations are needed to locate
the epicenter of an earthquake ( We will
do an activity to demonstrate this)
 Magnitude of an earthquake is a
measure of the amount of energy
released.
 The Richter scale is used to measure the
energy of an earthquake. ( An increase in
1 number is a 31-fold increase in energy)
Slide 9
A 7 earthquake has 31 times more energy
than a 6
 A 7 has 961 times more energy than a 5
(31 X 31)

Slide 10
Earthquake Hazards

Liquefaction occurs when loose soil
temporarily takes on the properties of a
liquid.
 Buildings located on this soil lose their
support.
Slide 11

Aftershocks often occur after the major
earthquake
 There can be up to 1000 aftershocks per
day.
 Underwater earthquakes and landslide can
cause tsunamis.
 Tsunamis can travel up to 750 km/hr in
deep water.
Tsunami photo
Slide 12
When earthquakes occur in populated
areas, infrastructure (roads, bridges,
water and gas pipes, communication
cables ) often suffer damage.
 This can lead to fires which are difficult to
put out.
