1. Earthquakes
Unit 12.2

2. sudden release of energy
Earthquake: shaking of the ground as a result of a ________________________ in Earth’s crust
often occurs as a result of _________ between moving tectonic plates that builds-up ____________
about 80% of earthquakes occur in a ring bordering the _______________
the Juan de Fuca convergent plate boundary West of Vancouver Island has many earthquakes
friction
pressure

5. sudden release of energy
Earthquake: shaking of the ground as a result of a ________________________ in Earth’s crust
often occurs as a result of _________ between moving tectonic plates that builds-up ____________
about 80% of earthquakes occur in a ring bordering the _______________
the Juan de Fuca convergent plate boundary West of Vancouver Island has many earthquakes
friction
pressure
Pacific Ocean

8. Classification of Earthquakes
location
Focus: _____________ where the pressure is finally released as an earthquake
Epicenter: the point on the ____________ ____________ _________ the focus
Earthquakes occur at various depths, depending on the plates involved.
earthquakes at the surface usually cause _______________
surface
directly
above
more damage
Classification of Earthquakes
Classification
Depth of Focus
Shallow
Focus 0 to 70 km
Intermediate
Focus 70 to 300 km
Deep
Greater than 300 km

10. vibration source strength
Seismic wave: _______________ energy released by earthquakes
can tell us the ___________ of an earthquake (where an earthquake happened)
can tell us the ____________ of an earthquake
source
strength

11. primary
wave
underground
solids
liquids
gases
fastest
Longitudinal
wave
1st
same
(P wave)

12. underground
secondary
wave
solids
slower
2nd
Transverse
wave
perpendicular to
(S wave)

13. surface only
solids
surface
wave
slowest
last (3rd)
perpendicular to
structural damage
(L wave)

15. composition size faster
Seismic waves can tell us the _______________ and _________ of Earth’s interior layers since they behave differently in different materials
some can travel underground
they travel _________ through solids than liquids
faster

16. The velocity increases
Since seismic waves travel faster through solids,
this must mean that the outer core is liquid

17. L S P P
mantle

18. arrival time long magnitude
Seismometer: a machine that measures and records seismic wave energy
Seismograph: a graph that shows
_______________ of seismic waves
how __________ an earthquake lasted
an earthquake’s ________________ (strength)
arrival time
long
magnitude

22. 5 min
3000 km

24. The magnitude (size) of an earthquake is the size of the line on the seismograph
The magnitude is measured by the Richter Scale
an increase of ____ in magnitude = _______ stronger 1
10x 10
102
103