Earthquakes are the
shaking, rolling or sudden
shock of the earth’s surface.
They are the Earth's
natural means of releasing
Earthquakes can be felt
over large areas although
they usually last less than
Earthquakes cannot be
scientists are working on it.
move they put
When the force
is large enough,
the crust is
forced to break.
When the break
stress is released
as energy, which
the Earth in the
form of waves,
which we feel
and call an
What is a fault?
fault is an area of stress in the earth where
broken rocks slide past each other, causing a
crack in the Earth's surface.
4 major types of faults which are as
follows: dip-slip normal, dip-slip reverse,
strike-slip, and oblique-slip.
Strike is long line, dip is short line
Note the angle of dip given 45o
Strike intersection w horizontal, dip perpendicular, angle from horizontal down toward surface
Reverse Fault Quake - Japan
DEMO – Types of faults
Strike Slip Fault Quake - California
Normal Fault Quake - Nevada
Earthquakes are caused by
sudden release of
accumulated strain energy
Rocks on sides of
fault are deformed
by tectonic forces
Rocks bend and
store elastic energy
the rocks together
is overcome by
• Earthquakes often occur when tectonic plate collide
• When two plates collide head-on, they push each other up and form
mountains. That's how the Himalayas and other great mountain ranges
(including the Rockies, long ago) were created.
These zones mark of edges of tectonic plates
•The point beneath the
Earth's surface where
the rocks break and
move is called the focus
of the earthquake.
•The focus is the
underground point of
origin of an earthquake.
Directly above the
focus, on the Earth's
surface, is the
• Earthquake waves are known as seismic waves
Seismometers instruments that record
Records the movement
of Earth in relation to a
stationary mass on a
rotating drum or
The first kind of body wave is the P wave or primary wave. This is the fastest kind of seismic
wave. The P wave can move through solid rock and fluids, like water or the liquid layers of the
earth. It pushes and pulls the rock it moves through just like sound waves push and pull the air..
The first kind of surface wave is called a
Love wave, named after A.E.H. Love, a
British mathematician who worked out the
mathematical model for this kind of wave in
1911. It's the fastest surface wave and
moves the ground from side-to-side.
S WAVES (SURFACE WAVES)
The other kind of surface wave is the
Rayleigh wave, named for John William
Strutt, Lord Rayleigh, who mathematically
predicted the existence of this kind of wave
in 1885. A Rayleigh wave rolls along the
ground just like a wave rolls across a lake or
an ocean. Because it rolls, it moves the
ground up and down, and side-to-side in the
same direction that the wave is moving.
Most of the shaking felt from an earthquake
is due to the Rayleigh wave, which can be
much larger than the other waves.
(Theses produce all
FACTORS EFFECTING THE DESTRUCTIVENESS OF AN
The more energy released, the greater potential for damage, regardless of all other factors (and
greater areal extent).
What Controls the Level of Shaking?
Shaking decays with distance
Local soils and bedrock geology
Soil characteristics may amplify the shaking.
(seasonal climatic variations can impact this)
Complex geology tends to dampen waves
Earthquakes: Facts and Fiction
Fiction: Earthquakes usually happen in the morning.
Fact: Earthquakes happen in both the day and the night.
There is no pattern.
Fiction: There is such a thing as "earthquake weather."
Fact: There is no connection between earthquakes and
weather. Remember, earthquakes happen deep in the earth,
far away from the weather!
Fiction: Earthquakes are on the increase.
Fact: It may seem like we’re having more earthquakes
because there are more reporting stations, but the truth is
Fiction: We can prevent earthquakes from happening.
Fact: No. You can protect yourself by doing things to secure
buildings, like your home, but earthquakes can’t be
prevented -- or predicted.