1. Warmup 1. What is an earthquake’s location on a surface called?
2. What is an earthquake’s location underground called?

2. 7.3 Earthquakes

3. Earthquakes
Earthquake- The shaking of the Earth’s crust cause by rapid displacement of rocks, usually along a fault.

4. Epicenter- the point on the Earth’s surface directly above the focus of an earthquake.
Focus- the point within the crust where an earthquake originates

5. Earthquake Waves

6. Body Waves
P-waves (primary or push-pull waves)- they cause back-and- forth motion in the same direction as the wave is traveling
S-waves (secondary or shear waves)- they cause motion at right angles to the direction in which the wave is traveling

7. Surface Waves
L-Waves (love or long waves)- travel along the Earth’s surface at slow speeds back and forth
R-Waves (Rayleigh waves)- travel along the Earth’s surface similar to an ocean wave

8. Measuring Earthquakes8

9. Seismic Waves- energy waves set in motion by an earthquake
Seismograph- an instrument used to record seismic waves

10. Paths of Body Waves P-waves travel faster than S- waves
Seismic waves travel faster through denser materials
Seismic wave bend (refract) as they move from a medium of one density into a medium of a different density
S-Waves will not travel through Earth’s outer core (which is liquid)

11. Earthquake Strength

12. Locating Epicenters
Find difference in travel time between P and S Waves
Use table to determine “distance from epicenter” for 3 seismograph stations
Epicenter is located where 3 circles intersect

14. Faults
Compression – the type of stress that occurs when an object is squeezed, such as when 2 tectonic plates collide.
Tension- the force (stress) that occurs when forces act to stretch an object.

15. Folding- the bending of rock layers due to stress
Two main types of folds:
Anticlines- upward arching folds
Synclines- downward
troughlike folds

16. Fault- the surface along which rocks break and slide past one another.
2 Main types of faults:
Normal faults- occur at divergent boundaries
Reverse faults- occur at convergent boundaries