1. Earthquakes

2. Anticipation Guide #4 Subduction occurs at divergent boundaries
Seismic waves are measured by how fast they travel
It takes 3 or more seismic stations to locate the epicenter of an earthquake
Convection occurs when heat is transferred in waves
All plate boundaries create volcanoes

3. VA SOL
SOL 8 The student will investigate and understand geologic processes…... Key concepts include
b. processes (faulting, folding, volcanism, metamorphism, …..) and their resulting features; and

4. Objective 4 Compare and contrast P, S, and L (surface) waves.
5 Identify how scientists locate an epicenter using earthquake data.
6 Evaluate the impact of earthquakes on human activities.

5. Enduring Understanding
Geologic processes produce characteristic structures and features

6. Earthquakes
One of nature’s most devastating occurrences is the earthquake. Earthquakes are capable of destroying entire cities and killing thousands of people in only a few seconds

7. Earthquakes
Earthquakes are natural vibrations of the ground caused by movement along fractures in Earth’s crust.

8. Earthquakes
Most earthquakes occur when rocks fracture deep within the Earth

9. Earthquakes
Stress is the force per unit area placed upon the materials and there are three different types

10. Earthquakes
Compression decreases the volume of a material

11. Earthquakes
Tension pulls the material apart

12. Earthquakes
Shear causes a material to twist

13. Earthquakes
Strain is the deformation of materials in response to stress

14. Earthquakes Waves
The vibrations in the ground during an earthquake are called seismic waves

15. Earthquakes Waves
Primary Waves (P-waves) squeeze and pull rocks in the same direction along which the waves are traveling

16. Earthquakes Waves
P-waves travel the fastest and CAN travel through liquids

17. Earthquakes Waves
Secondary Waves (S-waves) cause rocks to move at right angles to the direction of travel

18. Earthquakes Waves
S-waves travel slower than P-waves and CANNOT travel through liquids

19. Earthquakes Waves
Surface Waves (L-waves) travel only on the surface in two directions causing an up-and-down and side-to side motion

20. Earthquakes Waves
Most of the damage we see on the surface from earthquakes is caused by surface waves

21. Earthquakes Waves
Most of our knowledge of Earth’s interior comes from the study of seismic waves. The relationship between P-waves and S-waves allows us to measure the size of the inner and outer cores

22. Measuring and Locating Earthquakes
More than one million earthquakes occur each year. More than percent of these are not even felt by humans.

23. Measuring and Locating Earthquakes
Magnitude is the amount of energy released by an earthquake

24. Measuring and Locating Earthquakes
Richter Scale is the numerical scale to measure magnitude based on the size of the largest seismic waves generated

25. Measuring and Locating Earthquakes
Each number on the Richter scale represents an increase in amplitude by a factor of 10

26. Measuring and Locating Earthquakes
8 is ten times the amplitude of 7

27. Measuring and Locating Earthquakes
Modified Mercalli Scale measures the amount of damage done by the earthquake in Roman numerals I - - X II

28. Measuring and Locating Earthquakes
Earthquakes are located by tracking the seismic waves registered at different locations and plotting circles based on the speed of the waves and time elapsed

29. Measuring and Locating Earthquakes
Seismometers are sensitive instruments used to detect and record even the slightest vibrations of the earth’s surface

30. Measuring and Locating Earthquakes
Focus is the point of initial fault rupture and the location where the earthquake originates

31. Measuring and Locating Earthquakes
Epicenter is the point on the surface directly above the focus

32. Impact of Earthquakes
Earthquake activity has major impacts on human activities. Most of the damage caused by earthquakes comes from the prolonged shaking of the ground by surface waves, therefore structures in earthquake-prone areas are at risk.

33. Impact of Earthquakes
Structures built of brittle-unreinforced materials will are at risk of tipping or pancaking”

34. Impact of Earthquakes
Earthquake resistant buildings are now required in most advanced societies, but many poorer countries still allow tall structures to be built with substandard materials.. A recipe for disaster!

35. Impact of Earthquakes
Another major hazard of earthquake activity is the Tsunami (not tidal wave) generated by vertical motions of the seafloor

36. Impact of Earthquakes
Tsunami may appear as only one meter high in the open sea

37. Impact of Earthquakes
but they are an entire vertical column of water that grows to tens of meters high traveling between km/hr