1. Earthquakes and Landscapes

2. Objectives
Describe how earthquakes are produced by fault movement and how their strength is measured
Discuss the cause and behavior of tsunamis
Consider the types of damage that earthquakes produce
Relate the spatial pattern of earthquakes to plate tectonics
Introduce the landscapes and landforms that bear the signature of fault movement and earthquakes

3. What Produces Earthquakes?
Faults
A fracture in crustal rock where one side is displaced with respect to the other side

4. Earthquakes Stress is applied to a body of rock
Rocks deform while storing energy
Eventually stress becomes greater than the strength of the rock and the rock breaks
Energy is released in the form of seismic waves
Seismic waves radiate in all directions

6. Earthquakes Focus Epicenter The location where earthquakes originate
The point directly above the focus on the Earth’s surface

7. Measuring Earthquake Strength
Magnitude
Measures the amount of energy released
Seismograph
Instrument used to detect and record earth’s motion
Base anchored to the surface of the Earth and suspended weight records earth’s motion. © USGS

8. Measuring Earthquake Strength
Intensity
Measures the amount of shaking that has occurred
Determined by humans and property damage
The amount of shaking decreases with increasing distance from the focus – attenuation
Amplification occurs when the amount of shaking increases with distance because of loose sediment
Descriptive table of Modified Mercalli Intensity scale. © USGS

9. Tsunami Giant sea wave Commonly referred to a seismic sea wave
Produced by a sudden displacement of ocean water

10. Earthquake Damage Damage not proportional to magnitude
Damage proportional to population density
Alaska (1964)
9.2M resulted in 131 deaths
Haiti (2010)
7.0M resulted in 300,000 deaths

11. Earthquake Distribution
Majority of earthquake occur along plate boundaries
Greatest concentration along Circum-Pacific belt

12. Great Subduction Zone Earthquakes
9.0M+ and tsunami
Japan (2011)
4th strongest quake
Tsunami reached almost 30m (100 ft.)
Strongest earthquakes occur along subduction zones
Alaska (1964)
Chile (1960)
Sumatra (2004)

13. Intraplate Earthquakes
Earthquakes that do not occur along a plate boundary
Can potentially cause more damage because buildings are not built to withstand shaking

14. Earthquakes and Landscapes
Fault scarp
Exposed clifflike face
Fault plane
Contact surface along which blocks move on either side of a fault
Fault trace
Lower edge of a fault scarp