1. 7.1 Rocks Move Along Faults
A fault is a break or fracture in the __________ sphere, where blocks of rock move past each other.
Along parts of a fault, rocks may stick or lock together and bend as stress is put on them. The fault in the image above is a _________ fault.
_____________is the force exerted when an object presses on, pulls on, or pushes against another object.

2. As stress increases, the rocks break free.
The sudden release of stress in the lithosphere is called an ________________.
An earthquake is a shaking of the ground caused by the sudden movement of large blocks along a fault.
*Most earthquakes occur along _____ ________
because large amounts of stress build up as plates move.

3. ___________: the force that occurs
when two tectonic plates collide

4. Most earthquakes occur in the lithosphere because the tectonic plates are rigid and brittle, can break easily, and can move suddenly.

5. 7.2 Earthquakes Release Energy
All earthquakes start beneath Earth’s surface.
A _____ is the point underground where rocks first begin to move. (where the earthquake begins)
The _________ is the point on Earth’s surface
directly above the ________.

6. __________ waves are the vibrations caused by earthquakes.
As energy is released, it travels as _________ waves, outward in all directions.
__________ waves are the vibrations caused by earthquakes.
A _______ IS A DISTURBANCE IN A MEDIUM. Examples are a rock thrown in a pond, a sound, or light.

7. Shallow vs. Deep Focus
In general, if two earthquakes with equal strength have the same epicenter, the SHALLOW FOCUS will cause MORE DAMAGE, as seismic waves from the deep-focus earthquake lose more energy as they travel up to the surface.
Questions:
Why do the waves lose energy as they move to the surface?
If the plates are pushing together in the picture on this page, what sort of fault is this?
3. Is this type of fault likely to have deep earthquakes?

8. There are 3 types of Seismic Waves THAT WE’LL DISCUSS:
1. ______ Waves (P waves)
2. ________ Waves (S waves)
3. Surface Waves (There are Love and Rayleigh surface waves, but we will simply call them surface waves.)
P and S waves are known as _________ WAVES since they go through the body of the Earth, instead of along its surface.

9. As these waves travel through Earth, they ______ (bounce off of) boundaries between different layers.
The waves can also ______ (bend) as they enter a new layer.
Whether the waves reflect or refract depends on the angle that they hit the new layer(s) and the ________ of the new layer(s). (Same is true for light and sound waves!)

10. Properties of Primary Waves (P waves):
*Fastest and 1st to arrive (we use _______ km/sec)
*Can move through Solids, Liquids, and Gases
*Particles are slightly pushed together or pulled apart
in the direction of the waves’ travel.
*Buildings may experience push/pull in response
*One of the two types of ______ waves (with S waves)

11. Properties of Secondary Waves (S waves):
*Second to arrive
*Travel ½ the speed a primary waves (that’s __ km/sec)
*Particles move _____________ (right angle) to the
direction of the wave, causing small buildings to rock
back and forth
*ONLY TRAVEL THROUGH __________! (This is how
scientists realized our outer core is NOT solid!)
*One of the two types of body waves (with ___ waves)

12. Properties of ___________ Waves:
*Move along the SURFACE of the Earth
*As depth increases, motion from surface waves decreases, then stops
*Make ground roll up and down or shake side to side
*SLOWEST!
*BIGGEST GROUND MOVEMENT/MOST DAMAGE!!

13. Seismic Stations are placed all over the world to detect and measure ground ____________.
Seismographs are instruments that constantly record ground movements, both up and down and side to side.
Recordings produced by the seismograph
are known as ______________.
*Scientists use these seismograms to determine
locations and strengths of earthquakes. They need at least ___ to locate an “EXACT” location.

14. There are 2 types of seismographs, one to measure up and down movement and one to measure _____ to _____ movement of the ground.

15. 7.3 Earthquake Damage Can Be Reduced
There are 2 scales that measure earthquake strength:
*The Richter Scale
*The __________ ___________ Scale
The Richter Scale is based on how fast the ground moves (amount of energy) at the seismic station. Has accuracy issues for quakes above about magnitude _______ since it was developed for the ground in southern California where larger quakes are not expected due to it not being a subduction zone, but rather a _____________ boundary.
The Moment Magnitude Scale is based on the total amount of energy that is released by earthquakes.
Both scales show a top value of ______, but neither has an actual maximum value. Most scientists today prefer the Moment Magnitude Scale.

16. Moment Magnitude Effects Near Epicenter
An increase in one whole number on either earthquake scare indicates an increase of __ times more shaking and ____ times more energy
*GREATER MAGNITUDE = GREATER DAMAGE*
Moment Magnitude Effects Near Epicenter
Very Minor to Minor rarely noticed
Light slight damage
Moderate some structures damaged
Strong major damage to structures
Major some well-built structures
destroyed
8.0 and above Great major to total destruction

17. Damage from Earthquakes
_______________: a smaller earthquake that follows a more powerful earthquake.
_________: process where shaking of the ground causes certain soils to act like a liquid, causing buildings to topple or just sink into the ground. SEATTLE may look like the photo on the right some day.

18. Tsunami: large water “wave” caused by an earthquake.
Japan’s recent tsunami killed thousands and destroyed a __________ reactor, spreading contamination worldwide.
A tsunami in Indonesia killed 200,000 people in this century

19. Earthquakes Cause Damage, cont’d
A lot of damage from earthquakes is caused as the earth is ripped apart and fires start due to broken natural-gas lines, broken electrical power lines, or overturned stoves.
Most injuries and deaths are not caused by direct movement of the ground hurting people, but by collapsing buildings and other structures, fires, and the occasional tsunami. Dirty water and broken sanitation systems kill many more people in the months after major earthquakes.

20. Structures can be designed to resist earthquake damage
Many structures are shaken off of their foundations during an earthquake.
Building engineers use base isolators (left) to absorb ground motion and cross braces (right) for support and structure to buildings in locations of fault zones.