1. Earth Science
Chapter 5 Earthquakes

2. Forces in Earth's Crust
A force that acts on rock to change its shape or volume is stress
3 types of stress act on rock layers
Tension pulls on the crust
Compression squeezes rock
Shearing pushes a mass of rock in two opposite directions.

3. Tension –
Pulls on crust
Rock becomes thinner in the middle
Occurs at a spreading boundary

4. Compression –
Squeezes rock
Rock becomes thicker in the middle
Occurs at a colliding boundary

5. Shearing–
Pushes rock in two opposite directions
Occurs at a sliding boundary

6. Types of Force

7. Faults & Folds
Fault - a break in the rock layer of the crust where rock surfaces slip past each other.
Most faults occur at plate boundaries

8. 3 Types of Faults
Depends on the type of Stress applied to the rock layer
Foot wall & Hanging wall
Picture yourself as a little person, if this little person could hang off of one of the walls then that wall is the hanging wall. If the little person could place their foot on the bottom of the wall then it is the foot wall

10. Normal fault
Caused by tension
Hanging wall lies below the foot wall
Movement along vertical plane
Along spreading boundaries

11. Reverse fault
Caused by compression
Hanging wall lies above the foot wall
Movement along vertical plane
Along colliding boundaries

12. Strike Slip fault
Caused by shearing
Movement along horizontal plane
Along sliding boundaries

13. Types of faults

14. Rock Layers That Fold
Fold – Forces on the rock layer are not fast or strong enough to break or snap the rock but simply bends the rock layer
Caused by Compression type forces
Himalayas in Asia, Alps in Europe, and the north coast mountains of California are formed due to folding

15. A fold in rock that bends upward into an arch is an anticline.
A fold in rock that bends downward to form a valley is a syncline.
synclines
Anticlines

17. Fault Types & Land Forms
When two normal faults cut through a block of rock, fault movements may push up a fault-block

18. Earthquake!
A shaking and trembling that results from the sudden movement of part of the Earth’s crust.
Similar to ripples from a pebble in a pond
Usually occur along a fault
More than 1 million per year on the planet
Entire fault doesn’t all move at the same time. Energy is released at different places at any one time

19. Earthquake Terms
Focus: the point underground where the release of stress is located
Epicenter: the point on the earth’s surface directly above the focus
Aftershock: an earthquake that occurs after a larger earthquake in the same area.
Liquefaction: earthquake's violent shaking suddenly turns loose, soft soil into a liquid-like slurry.

22. Seismic Waves
Seismic waves: carry energy from an earthquake away from the focus
P waves
S waves
Surface waves

23. Primary Waves: P waves
1. Fastest moving of the waves
2. Travel through solid, liquids and gases
3. “Push-pull” type of wave

24. Primary Waves: P waves

25. Secondary Waves: S Waves
1. Second to arrive
2. Travel through solid but not liquid or gas
3. “S” shaped waves
4. Rock particles move at right angles to the direction of the wave

26. Secondary Waves: S Waves

27. 2. Travel across the surface of the Earth
Surface Waves
1. Slowest moving of the waves
2. Travel across the surface of the Earth
3. Originate on the earth’s surface
4. Cause the most damage of all the waves

28. Surface Waves: L Waves

29. Seismic Wave Movements
P waves travel thru solid & liquid.
P waves arrive first then come the S waves
S waves reflect off the liquid outer core

30. Earthquake Strength & Intensity
Richter Scale - rating of an earthquake's magnitude based on the size of the earthquake's seismic waves ( 1 – 10)
Mercalli Scale - rate earthquakes according to the level of damage at a given place. ( I – XII)
Moment Magnitude Scale - rating system that estimates the total energy released by an earthquake

31. Richter Scale Most commonly used scale
Each number represents a magnitude 10x greater than previous number.

32. Mercalli Scale
rate earthquakes according to the level of damage at a given place. ( I – XII)

33. Seismograph
A Seismograph detects and measures intensity of the earthquake
A Record of an earthquake is a seismogram

34. To monitor faults, geologists use instruments to measure –
Changes in elevation
Tilting of the land surface
Ground movement along faults

35. Instruments that Monitor Faults
Tilt Meters – vertical movement
Creep Meters – horizontal movement
Laser-ranging Devices – horizontal movement
GPS Satellites – vertical and horizontal movement

36. Earthquake Safety Geologists determine earthquake risk by –
Locating where faults are active
Where past earthquakes have occurred
Where most damage was caused

37. How Earthquakes Cause Damage
Shaking –
damage buildings, utility poles, fracture gas lines, cause landslides, avalanches
Lose soil shakes more than solid rock – house built on sandy soil will shake more than the one built on solid rock

38. 2. Liquefaction –
Where soil is full of moisture – as ground shakes, lose soil becomes liquid mud – foundation becomes weak

39. Aftershocks – Earthquake that occurs after a larger earthquake in an area – buildings are already weakened

40. Tsunamis
Tsunami - a large water wave caused by an under sea earthquake.
When an earthquake jolts the ocean floor, plate movement causes the ocean floor to rise slightly and push water out of its way.

41. Earthquake Safe Buildings
Type of material
Size of building

42. Making buildings safer –
Base isolated buildings
Base isolators
Tension ties
Shear walls
Cross bracing
Dampers
Flexible pipes

43. Earthquake song - https://www.youtube.com/watch?v=sA6oZ4YgKCA
Shake table – base isolation -