Chapter 19 1 earthquakes
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Chapter 19.1 EARTHQUAKES. F orces within earth. Earthquakes . Natural vibrations of the ground caused by movement along fractures in the crust or volcanic eruptions Fractures form when stress exceeds the strength of the rock. Types of Stress. Tension- pull Compression- push Shear- twist

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Chapter 19 1 earthquakes

Chapter 19.1 EARTHQUAKES

Forces within earth


Earthquakes
Earthquakes

  • Natural vibrations of the ground caused by movement along fractures in the crust or volcanic eruptions

  • Fractures form when stress exceeds the strength of the rock


Types of stress
Types of Stress

  • Tension- pull

  • Compression- push

  • Shear- twist

  • Strain- deformation caused by stress


Ductile deformation
Ductile Deformation

  • Elastic deformation occurs as a result of low stress

  • Ductile deformation occurs when stress is high

  • When does fracture occur?


Faults
Faults

  • Fractures in the Earth’s crust along which movement occurs


Types of faults
Types of Faults

  • Normal- tension

  • Reverse- compression

  • Strike-slip- shear


Seismic waves
Seismic Waves

  • (Primary) P-waves- squeeze and pull rocks in the same direction of the waves

  • (Secondary) S-waves- cause rock to move at right angles to the direction of the waves

  • Surface waves- cause rock to move up & down



Chapter 19 2 earthquakes

Chapter 19.2 EARTHQUAKES

Seismic waves & earths interior


Seismology
Seismology

  • Study of earthquake waves

  • Seismograph/seismometer- register the vibrations

  • Seismogram- the record of vibrations


Travel time
Travel- time

  • Travel time for P and S waves differ

  • Can you tell which ones reach a location first?

  • Where is the biggest difference in the time one wave arrives before the other?


Clues to earth s interior
Clues to Earth’s Interior

  • P waves are refracted in the core

  • S waves can not travel through liquids

  • Behavior of waves provide details of Earth’s interior structure and composition


Chapter 19 3 earthquakes

Chapter 19.3 EARTHQUAKES

Measuring & locating earthquakes


Earthquake magnitude and intensity
Earthquake Magnitude and Intensity

  • Magnitude- the amount of energy released during an earthquake

  • Richter scale- earthquake rating based on the size of the largest seismic waves

  • Increases by power of 10 for each magnitude


Moment magnitude scale
Moment Magnitude Scale

  • Most used today

  • Based on the size of the fault rupture, amount of movement along the fault, and the rocks’ stiffness


Modified mercalli scale
Modified Mercalli Scale

  • Based on the amount of damage done to structures

  • Measure of intensity



Locating an earthquake
Locating an Earthquake

  • Distance from epicenter is calculated by comparing the separation time between P and S waves

  • 3 locations are needed to accurately determine the epicenter of the earthquake

  • Why?


Seismic belts
Seismic Belts

  • 80% occur in the Circum-Pacific Belt

  • 15% occur in the Mediterranean-Asian Belt


Chapter 19 4 earthquakes

Chapter 19.4 EARTHQUAKES

Earthquakes & Society


Earthquake hazards
Earthquake Hazards

  • Structural Failure

    • Pancaking

    • Collapse

2010 Pichilemu earthquake in Chile

1999 Izmit earthquake in Turkey


Earthquake hazards1
Earthquake Hazards

  • Land and Soil Failure

    • Liquifaction

    • Seismic wave amplification


Liquifaction in christchurch nz
Liquifaction in Christchurch, NZ


Earthquake hazards2
Earthquake Hazards

  • Fault Scarps

    • Vertical offset




Earthquake prediction
Earthquake Prediction

  • History

  • Strain Accumulation


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