1. Earthquakes

2. Earthquakes
Earthquakes are a sudden release of vibrations and energy in the Earth’s crust
Can happen along any type of plate boundary
Can be very small and cause no damage or very large and catastrophic

3. Where are earthquakes likely to occur?
Along plate boundaries
Along faults
In volcanic regions

4. Faults
A fault is a fracture in the Earth’s crust that occurs when stress is applied too quickly

5. Reverse Faults When 2 blocks are pushed together due to compression
One slides up relative to the other
Can cause tsunamis

6. https://www.youtube.com/watch?v=4b81nXSVA3 4

7. Normal Faults When 2 blocks of rock are pulled apart by tension
One slides down relative to the other

9. Transform or Strike Slip Faults
Occur as a result of shear stress
Scrape past each other in opposite direction
San Andreas Fault (San Francisco)

13. 1992 – 7.3 Magnitude

16. Parts of an Earthquake
The Focus is the point where an earthquake originates. Waves travel out from the focus like ripples in a pond
The epicenter is the point on Earth’s surface directly above the focus.

17. Fault line
Epicenter
Focus

18. Complete the stop and think

19. How do we measure Earthquakes?
Using seismographs or seismometers
Measure the amount of force and the length of shaking
Measure the vibrations and shaking of the crust

20. Earthquake Waves The vibrations during an earthquake are called seismic waves
Primary Waves- move in a push pull motion
Can move through solids and liquids
The fastest and the first
Secondary Waves- move in a side to side motion
Can only move through solids
Arrive second
Surface Waves- from when the s and p waves reach earth’s surface
Slowest and last
Most destructive

22. Time Travel Curves P Waves are always detected first(move faster)
With increasing distance there is a greater difference between the arrival time of P and S waves
The difference in arrival time between p and s waves can determine how far away the earthquake is

25. Earthquake magnitude
The Richter Scale measures the amount of energy released during an earthquake
Scale goes from
The waves generated by a 4 are 10X larger than the waves generated by a 3
Largest earthquake ever recorded was a 9.5 in Chile in 1960.