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Landforms
Earthquakes
Mountains
A mass of rock rising more than 600
meters above the surrounding land
Relief
Fold Mountain
formation
Appalachian Mountains
Rocky Mountains
Alps
Himalaya Mountains
Fault-Block Mountain
formation
Fault Block Mountain
Ranges are cause by a
series of normal faults
Sierra Nevada Mountains, CA
Grand Tetons, WY
Wasatch Mountains, Utah
When the Earth SHAKES
Earthquakes
Volcanic eruptions can cause
earthquakes but most
earthquakes are caused by
FAULTING
The Elastic Rebound Theory was
first proposed by American
geologist
Harry Fielding Reid
after the 1906 San Francisco
Earthquake
Seismic Waves are waves of
vibration sent out in all directions
from the FOCUS
Focus
The point below the surface where
the rock layers break and move
Epicenter
The point on the surface, directly
above the focus. Where the greatest
damage usually occurs
Measuring Earthquakes
Charles Richter
Early Seismograph
Newton’s First Law
Seismograph- the machine that
measures earthquake waves
Seismogram – the recorded
information of earthquake waves
The Richter Scale is based on
MAGNITUDE
Magnitude 1
Magnitude 2
Magnitude 3
Each # is TEN TIMES larger
than the # before it…
Pennies as an example:
Mag. 1 = 1 penny
Mag. 2 = 10 pennies
Mag 3 = 100 pennies
Mag. 4 = 1000 pennies
Mag. 5 = 10,000 pennies
Mag. 6 = 100,000 pennies
Mag. 7 = 1,000,000 pennies
Mag. 8 = 10,000,000 pennies
Mag. 9 = 100,000,000 pennies
Mag. 10 = 1,000,000,000 pennies
(that’s $10 million in pennies!!)
Richter Magnitudes
Earthquake Effects
Less than 3.5
Generally not felt
3.5-5.4
Often felt, little damage
Under 6.0
Slight damage to buildings
6.1-6.9
Can be destructive to about
100 km
7.0-7.9
cause
Major earthquake. Can
serious damage
8 or greater
Large earthquake. Serious
damage for hundreds of km
Anatomy of a basic wave
Crest – the highest point on a wave (A, F)
Trough – the lowest point on a wave (D, I)
Amplitude – the distance between the midpoint &
crest or trough
Wavelength – distance between any two successive
points on a wave
Frequency - # of vibrations/ second (Hertz)
Types of Seismic Waves
Body Waves are
waves that travel
through the body of
the earth
Surface waves only
travel along the
surface of earth
Body Waves
Primary Waves
AKA P-Wave
Type of Longitudinal Wave
Causes back and forth motion
Follows the same direction as the
energy transfer
P-Waves
Type of COMPRESSIONAL wave (like sound)
Will travel through solid, liquid or gas
Travels at:
7.8 – 8.5 kps in mantle
7.2 kps in oceanic crust
3.5 kps in continental crust
Primary Wave
Secondary Wave
AKA S-Wave
Particle motion is perpendicular to
direction of energy transfer
Transverse or Shear Wave
Will travel only through solids
Travels 4 – 5 kps
Secondary Wave
Surface Waves
Love Wave
Recent evidence show s that L-Waves attenuate
(gradually disappear) more slowly in older rock
(eastern US) and more quickly in
younger rock (western US)
Two main types of surface waves:
Love Wave
Rayleigh Wave
Love Waves travel less than 4 kps
Move side-to-side; like a snake
Causes the most damage
Seismogram with the PWave, S-Wave and L-Wave
Seismic Risk in the US
Triangulation
Refraction
Refraction of seismic waves
within the Earth
Zone between about
105 degrees & 145 degrees
is the Shadow Zone
Focus
105 degrees
145 degrees