1. Earthquakes

2. What is an earthquake?
Used to describe both sudden slip on a fault, and the resulting ground shaking and radiated seismic energy caused by the slip
Caused by volcanic or magmatic activity,
Caused by other sudden stress changes in the earth.

3. Why do earthquakes happen?

4. Why do earthquakes happen?
Shockwaves, pressure, earth, shake, focus, epicentre, plates
Why do earthquakes happen?
Stage 1: Two of the crusts ___________ rub against each other and stick in one place. __________ _builds up as they try and move past each other.
Stage 2: Suddenly, the pressure is too much and the plates jerk past each other. The place where this happens is called the ______________.
Stage 3: Vibrations go out in all directions through the rocks. These vibrations are called ______________.
Stage 4: When the shock waves reach the surface of the _____________ they cause the ground to ______________. The most violent shaking is directly above the focus at a point on the Earths surface called the ________________.
Plates
Pressure
Focus
Shockwaves
Earth
Shake
Epicenter

5. What causes earthquakes?
Tectonic plates move past each other causing stress. Stress causes the rock to deform
Plastic deformation – does not cause earthquakes
Elastic deformation – rock stretches then reaches a breaking point, releasing energy.

6. Elastic Rebound – deformed rock goes back to its original shape

7. Focus –. point inside the Earth where an
Focus – point inside the Earth where an earthquake begins Epicenter – point on Earth’s surface above focus

8. How Seismographs Work
the pendulum remains fixed as the ground moves beneath it

9. Typical Seismogram

10. Primary Waves (P Waves)
A type of seismic wave that compresses and expands the ground
The first wave to arrive at an earthquake

11. Secondary Waves (S Waves)
A type of seismic wave that moves the ground up and down or side to side

12. Comparing Seismic Waves

13. Surface Waves Move along the Earth’s surface
Produces motion in the upper crust
Motion can be up and down
Motion can be around
Motion can be back and forth
Travel more slowly than S and P waves
More destructive

14. How do scientists calculate how far a location is from the epicenter of an earthquake?
Scientists calculate the difference between arrival times of the P waves and S waves
The further away an earthquake is, the greater the time between the arrival of the P waves and the S waves

15. Locating Earthquakes

16. Locating Earthquakes

17. Locating Earthquakes

18. How are Earthquakes Measured? Richter Scale

19. How are Earthquakes Measured? Mercalli Intensity Scale
Click Link for Interactive Demo

20. Earthquake Waves & Earth’s Interior

21. Seismic Waves in the Earth

22. Tsunamis

24. Formation of a tsunami

25. Tsunami Warning System