1. Section: 1: Forces inside Earth
Chapter 5: Earthquakes
Section: 1: Forces inside Earth
Objectives:
Explain how earthquakes result from buildup of energy in rocks
Describe how compression, tension, and shear forces make rocks move along faults
Distinguish among normal, reverse, and strike-slip faults

2. Rough Outline Earthquake Causes A. Fault Formation
B. What Causes Faults
C. How Earthquakes Occur
Type of Faults
A. Normal Faults
B. Reverse Faults
C. Strike-Slip Faults

3. Frequency of occurrence
Richter magnitudes
Description
Earthquake effects
Frequency of occurrence
Less than 2.0
Micro
Microearthquakes, not felt.
About 8,000 per day
Minor
Generally not felt, but recorded.
About 1,000 per day
Often felt, but rarely causes damage.
49,000 per year (est.)
Light
Noticeable shaking of indoor items, rattling noises. Significant damage unlikely.
6,200 per year (est.)
Moderate
Can cause major damage to poorly constructed buildings over small regions. At most slight damage to well-designed buildings.
800 per year
Strong
Can be destructive in areas up to about 160 kilometers (100 mi) across in populated areas.
120 per year
Major
Can cause serious damage over larger areas.
18 per year
Great
Can cause serious damage in areas several hundred miles across.
1 per year
Devastating in areas several thousand miles across.
1 per 20 years
10.0+
Epic
Never recorded; see below for equivalent seismic energy yield.

4. Haitian Capital, Port-au-Prince January 14, 2010

5. Earthquake measured 7.2

7. More than 100,000 died

12. Injured people outside the Villa Creole the day after the earthquake

13. An aerial view of the UN headquarters in Haiti shows how the office complex was devastated by the earthquake

15. The Haitian national palace shows heavy damage following the earthquake. The city's airport was operational, opening the way for international relief aid to be ferried in

16. People search for survivors under the rubble of a collapse building the day after the quake

17. A women and her injured baby are seen at a makeshift field hospital in Port-au-Prince

18. A shanty town on the outskirts of Port-au-Prince where thousands of dwellings were either completely destroyed or badly damaged

19. Haitians set up impromtu tent cities thorough the capital after the earthquake

20. Show Haiti Video from Favorites

21. Earthquake in Chili February 27, 2010

31. Play two favorites news videos

32. Is it likely we will encounter an earthquake of this magnetite?NO
Take a look at the plate boundaries and take a look at where we are located!!

33. Earthquake Causes Fault Formation
Elastic limit: the limit to how far something can bend
Elastic Deformation: the forces that cause rocks to bend and stretch.
Faults: Surface along which rocks move when they pass their elastic limit and break.

34. What causes faults?
The forces inside the Earth cause plates to move and shift – causes earthquakes.
Earthquake: The vibrations produced by the breaking of rock
Earthquakes are most likely to happen near the plates because most stress in as boundaries where plates meet.

35. How Earthquakes Occur
1. As plates move past each other their rough surfaces sometimes catch.
2. Forces continue to build up where the rocks are stuck
3. The stress causes rocks to bend and change shape
4. When the rocks are stressed beyond their elastic limit they break and move along a fault to return to their original shape
5. THIS CREATES AN EARTHQUAKE!!!!!

36. Earth’s crust is in constant motion
Places stress on rocks
Rocks bend & stretch like a rubber band
Break
Produces vibrations called EARTHQUAKE

37. II. Types of Faults A. Normal Fault Force – tension Plates move apart
Rock moves downward

38. On the east coast of California
Sierra Nevadas
On the east coast of California

39. B. Reverse Fault Force – compression Plates come together
Rocks at the surface are forced up & over the ones below the surface

40. Rocky Mountain National Park

41. C. Strike-slip Fault Force – shear
Plates move sideways past each other
Rocks on either side move past each other

42. San Andreas
Fault