1. Causes:
A. plate tectonics (elastic rebound theory)
 faults “stick”  buildup of energy 
when they slip lots of energy is
released = EARTHQUAKE
B. glacial rebound theory
 heavy glacier compresses ground 
ground springs back up =
EARTHQUAKE
2. Earthquake terms:
Focus: origin of energy release (deep underground)
Epicentre: point on surface above the focus
Liquifaction: when land turns to mud when shaken
Tsunami:
giant wave resulting from earthquake in
ocean
low in ocean, but fast moving
friction slows it down as it nears shore
grows up to 80 m high!!
Diagram of science!
Aftershocks: minor faults nearby breaking loose
follow major quakes
Seismic waves: 3 types of waves emitted from
earthquakes
1. P – wave (primary)


push / pull
(compressional wave)
moves fast
3. L – wave (Love)


2. S – wave (secondary)


side-to-side motion
(“shear” wave)
moves more slowly


rolling motion
last to arrive
travels along surface of
Earth
most damaging
3. Finding the Epicentre of an Earthquake:
The distance between the P & S – waves increases
as waves travel outward from the epicentre.
How much time that passed between the detection
of the P & S – waves can be used to determine
how far away the epicentre was.
With 3 stations
calculating
distances to the
epicentre of the
earthquake, the
epicentre can
be pinpointed.
Homework:

Textbook Page 531, “Reading Check”,
 Questions

1-3
Virtual Seismologist Activity
2
Earthquake Certificates must be printed /
emailed with your name on them
(can’t do San Francisco)

http://nemo.sciencecourseware.org/VirtualEarthquake/VQuakeExecute.html