1. Earth
quake!

2. Haiti Earthquake
Chile Earthquake
chile ppt.ppt

3. What is an Earthquake?
A shake or vibration caused by the sudden breaking or sliding of rock in the Earth

4. Fault - Fracture (break) in rock where sliding occurs
Where do they happen?
Fault - Fracture (break) in rock where sliding occurs
As tectonic plates move, they slide past other plates. At the edges they get stuck, but the plates keep moving. Eventually, the rock gives and a fault is formed.

5. Stress builds up between the two plates causing the crust to warp
Elastic Rebound
Stress builds up between the two plates causing the crust to warp
An earthquake allows that energy to be released, and the plates return to their normal position (just shifted)

6. Stages of an Earthquake
Inactivity
(1 ½. Foreshock small quake that can occurs hours or days before a major earthquake)
2. Major Earthquake
3. Aftershock quakes that occur seconds to a year after a major earthquake

7. TYPES OF FAULTS
Normal Fault
Reverse Fault
Strike Slip

8. -blocks of rock move apart -occur at divergent boundaries
Normal Fault
-blocks of rock move apart -occur at divergent boundaries

9. Reverse Fault
-blocks of rock move towards each other -occur at convergent boundaries

10. -rocks move sideways past each other -occur at transform boundaries
Strike Slip
-rocks move sideways past each other -occur at transform boundaries

12. Earthquakes don’t always occur along a plate boundary…
New Madrid Fault
3 Magnitude 8 Earthquakes

15. How do we measure earthquakes?
Richter Scale
-measures the height of seismic waves
-each whole number is 10 times the seismic wave height
-each whole number is 33 times more energy released

16. Richter Scale > 8 Total destruction About 1/year 7-7.9 Bad 18/year
6-6.9
Moderate -serious
120/year
5-5.9
Minor damage (felt by everyone)
800/year
4-4.9
Not felt by everyone
6,000/year
< 3.9
Very small
1 million/year

18. Largest Earthquake on the Richter Scale:
9.5
Chile
1960

19. How do we measure earthquakes?
2. Mercalli Intensity Scale -the amount of damage an earthquake causes
-scale of I - XII
-very subjective
-typically used for building codes

20. Mercalli Scale

21. How do we measure earthquakes?
3. Moment Magnitude Scale -combine how rigid the Earth is and the distance the Earth moves along the fault
-scientists use this method the most

22. Predicting an Earthquake
Short-term ‘Forecasting’
-hours to weeks
-based on foreshocks
*not always foreshocks

23. Predicting an Earthquake
2. Seismic Gap
-areas along faults that have not had recent earthquakes
-the more time without an earthquake, the greater the chance of an upcoming earthquake
-larger earthquakes in the past -> more frequent earthquakes

24. Predicting an Earthquake
3. Recurrence Interval
-earthquakes along a fault tend to have relatively constant recurrence patterns
ex: San Andreas Fault
-22 years between earthquakes of magnitude 5.5 or higher

25. Predicting an Earthquake
4. Anomalous Animal Behavior
-dogs barking
-chickens not laying eggs
-rats perched on power lines
*not considered scientific* though often evident

26. Deadliest Earthquakes
1. Shaanxi, China ,000 casualties
2. Tangshan, China 1976 – 255,000 casualties
3. Gansu, China 1920 – 234,117 casualties
4. Haiti ,000 casualties
5. Indian Ocean (Sumatra) 2004 – 230,210 casualties

27. Tangshan, China
Animals also gave a warning that something was about to happen. One thousand chickens in Baiguantuan refused to eat and ran around excitedly chirping. Mice and yellow weasels were seen running around looking for a place to hide. In one household in the city of Tangshan, a goldfish began jumping wildly in its bowl. At 2 a.m. on July 28, shortly before the earthquake struck, the goldfish jumped out of its bowl. Once its owner had returned him to his bowl, the goldfish continued to jump out of its bowl until the earthquake hit.
Chen Yong, et al, The Great Tangshan Earthquake of 1976: An Anatomy of Disaster (New York: Pergamon Press, 1988) 53.

28. Human Induced Earthquakes
Several earthquakes have been caused because of human activity
Examples: -building dams over inactive fault zones (e’quake and flooding)
Nuclear Explosions (Nevada test site)
*Some scientists think we should trigger ‘controlled quakes’ in California to reduce potential damage

29. As energy is released from an earthquake, it is distributed in waves
Seismic Waves
As energy is released from an earthquake, it is distributed in waves

30. Seismic Waves Body Waves Surface Waves
Travel through the interior of the Earth
Surface Waves
Travel along the Earth’s surface

31. Body Waves P - Waves Primary Waves ‘pressure’ or ‘push – pull’ waves
Travel fastest (few km/sec)
Travel through all layers of Earth

32. Body Waves S – Waves Secondary Waves ‘shear’ or ‘shape’ waves
Travel slightly slower than P waves
Do not travel through liquids (outer core)

33. Body Waves

34. Make the ground ripple up and down
Surface Waves
R - Waves
Rayleigh Waves
Make the ground ripple up and down

35. Make the ground ripple side to side
Surface Waves
L - Waves
Love Waves
Make the ground ripple side to side

36. Seismograph
An instrument that can record ground motion from an earthquake happening anywhere on Earth

37. Locating an Earthquake
Focus Spot in the crust where the fault begins to slip
*the deeper an earthquake, the less damage it causes at the surface*
Epicenter Point on Earth’s surface directly above the focus

38. Locating an Earthquake
How to find an epicenter
-need 3 seismic stations to record the event
-using the differences in arrival times, seismologists can determine the distance of the station to the epicenter

39. Triangulation
When you connect the data from the 3 seismic stations, you will find the epicenter

40. Earthquake Aftermath
Earthquakes themselves cause tremendous damage, but they also leave behind a path of destruction

41. Depending on the fault, giant cracks in the Earth can form
1. Ground Displacement
Depending on the fault, giant cracks in the Earth can form
Alaska 1964
Examples:
1964–Alaska– 12 m
1906–San Francisco– 7 m

42. 2. Landslides
Soil and Debris that is shaken during an earthquake may loosen and cause a landslide

43. 3. Liquefaction
Soil that has small amounts of water in it, will act as a liquid during an earthquake
Ex: Kobe, Japan 1995

44. 4. Tsunami Seismic sea wave
Earthquakes that occur near oceans create massive waves which act as a wall of water
Sumatra 2004

45. Destruction during an earthquake can cause large fires
Tokyo
San Francisco