Transcript Chapter 6 – Earthquakes Part 3

Chapter 6 – Earthquakes Part 3
 Earthquake Destruction.
The largest quake recorded to date has been
the 1960 Chilean quake - 8.6. The largest
North American quake is the 1964 Alaskan
quake - 8.4 and it lasted 3-4 minutes with
28 aftershocks, 10 at magnitude 6.
 What does it all add up to?
Factors Affecting
Structural Damage
1. The amplitude of the waves.
2. The duration of the quake.
3. The type of material the structures are
build on.
4. The design of the structure.
See page 166.
Seismic Waves and Liquefaction
 Liquefaction is the liquification of
seemingly solid ground. It results when
unconsolidated material like glacial till
become saturated by water.
 The shaking causes the materials to mix
with the water creating a “soup”.
 The result is sinking buildings and rising
tanks.
Tsunami
Not Another A Japanese Car
 Seismic sea waves
It is Japanese for harbour wave. They result from
the vertical displacement of the ocean floor.
The energy is transmitted to the water. In the
open ocean, they may not appear to be very
large, but a they approach land, water piles
upward, creating huge towering waves.
See page 169-170
Landslides and Ground Subsidence
 It goes without saying that if the ground
shakes, landslides will result.
 Ground subsidence occurs when water
replaces land due the slipping of large land
masses into lake or the ocean.
Fire!
 Identify some probable sources of fire duing
or after a destructive quake.
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The Earth’s Interior (Again!)
 What can earthquakes tell u about the
earth’s interior?
 Since drilling limits how deep we can go,
seismic waves can tell u a lot.
 The characteristics of p and s waves, like
their speeds and what they travel through.
 Knowledge of the focus and multiple
seismic readings of quake have given us the
following structure of the earth:
 Four Layers
1. The crust – outer most layer ~100 km
thick.
2. The Mantle – rocky layer beneath the
crust, with areas of molten rock ~ 2885km
thick.
3. The Outer Core – molten layer composed
mainly of iron and nickel ~ 2270 km
thick.
4. The Inner Core – solid metal, iron and
nickel ~ 1216 km thick
Just Call Me Moho!
 The Mohorovicic Discontinuity, the boundary
between the crust and the mantle, was found using
seismic waves.
 Another zone discovered was the p-wave shadow
zone where p-waves tend to die out. This results
because of sudden changes between the mantle
and outer core. The p-waves bend and change
direction, causing a zone between 105 and 140
degrees. See p.173
Asthenosphere and Lithosphere
 The asthenosphere is the plastic upper
layer of the mantle capable of flowing.
 The lithosphere is the solid cool layer
above the asthenosphere which includes the
crust.
See page 175.
Now sketch it all together!