EESA06 Chapter #3 Textbook Notes
Notable Historical Earthquakes
Charlevoix-Kamouraska Seismic Zone in Quebec, 1663 and 1870 (First earthquakes ever
documented in North America)
1929 Eastern Canada, Triggered a tsunami killing 28, scientist we able to record speed of the
1906, a 450km long scar was visible on northern California coast. 3000 people died and $400
million of damage was caused by the earthquake. Most of the damage was caused by fires.
1989, earthquake hit San Francisco. Death toll 63 people and $.6 billion in damages.
1964, earthquake rocked southern Alaska. This earthquake was twice as strong as 1906 San
Francisco earthquake. 15 people died and $300 million in damages. Tsunami was created and
felt across Pacific Ocean.
1994, San Fernando Valley, north of Los Angeles was hit with earthquake. Highways and
buildings were damaged. 16 people died when apartment collapsed and $25 billion in damages.
2002, Alaska on the Denali fault was the largest earthquake ever recorded. No deaths and
2004, 9.3 magnitude earthquake deformed the Indian Ocean and caused more casualties than
any other earthquake before.
What Causes Earthquakes
Earthquakes Trembling or shaking of ground caused by sudden release of energy stored in
rocks in Earth’s interior.
Seismic Waves Waves of energy produced by earthquakes.
Elastic Rebound The sudden release of progressive stored elastic strain energy in rocks, causing
Theory movement along a fault.
Called the elastic rebound theory in which tectonic forces act on a mass of rock over many
decades. As more energy is stored onto the rock, the energy stored in the rock eventually
exceeds the breaking strength of the rock. The rock breaks suddenly, causing an earthquake.
Implied that existing forces are strong, a very large stress must act to break rock along a fault.
Faults are weak, and need only a small stress to cause rupture and earthquake. Suggestive idea but not conclusive. This weak-fault model poses serious problems for
Earthquakes in eastern North America are not associated with surface displacement. Earthquakes can
occur during volcanic eruptions and as magma forcibly fills underground magma chambers prior to
eruptions. Earthquakes don’t always have to be associated with fault movements.
Focus The point within earth where seismic waves first occur.
Epicentre Point on Earth’s surface directly above focus.