Earthquakes
Earth’s Hypsometry and Topography
Continental Shields
Crustal Formation
Figure 9.5
North American
Terranes
Much of Vancouver
Island was once found
near the equator
Two types of crust “float”
on the upper mantle
1. Oceanic crust (heavier, sinks lower)
2. Continental crust (lighter, floats higher)
Three types of plate convergence
1. Oceanic – continental
2. Oceanic – oceanic
3. Continental - continental
Oceanic – continental plate convergence
Nazca plate – South America plate
Oceanic – oceanic plate convergence
New Hebrides Trench near Vanuatu
Continental – continental plate convergence
India/Eurasia plate collision
(forms Himalayan Mountains)
Stress build-up and release
Earthquake Motion
Horst and Graben: faulted blocks
Historical seismic activity in Canada
Haiti Earthquake: January 2010
1906
San Francisco
Earthquake
San Andreas
Fault
Mercalli
Richter
1964 Alaska earthquake damage
map: modified Mercalli scale
III - IV
V
VI
VII
VIII - X
Liquefaction and slumping
Anchorage, Alaska - 1964
Earthquake-proof buildings
•Pressure is not always great enough or
abrupt enough to cause faulting
(earthquakes).
•Deformation occurs (FOLDING) if pressure does not
exceed the internal strength of the rock or if it
becomes plastic (hot).
•Tensional stress produces thinning crust, folding
and normal faults
•Compressional stress produces thickening crust,
folding and reverse faults
•Shearing stress produces horizontal bending and
strike-slip faults
Zagros
Crush
Zone
Domes and Basins
Figure 9.10
Is a major earthquake in
California, Alaska or Japan
of any concern thousands of
kilometers away, in Hawaii?
Hint:
In Fall 2004, no one answered
this question, but many could in
Spring 2005.
(seismic wave)
Source: CTV, Jan 2005
December 2004 Tsunami: Indonesia, Thailand, Sri Lanka
The power of a tsunami