earthquakes. what is an earthquake? used to describe both sudden slip on a fault, and the resulting...
TRANSCRIPT
Earthquakes
What is an earthquake?
• Used to describe both sudden slip on a fault, and the resulting ground shaking and radiated seismic energy caused by the slip
• Caused by sudden stress changes in the earth.• Usually occur at or near plate boundaries• Some are strong and can be felt on the
surface, some are weak and can only be felt by a seismograph
Three Types of Faults
Strike-SlipReverse
Normal
What causes earthquakes?• Tectonic plates move past each other causing
stress. Stress causes the rock to deform– Plastic deformation – does not cause earthquakes– Elastic deformation – rock stretches then reaches
a breaking point, releasing energy.
Elastic Rebound – deformed rock goes back to its original shape
http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM
Focus – point inside the Earth where an earthquake beginsEpicenter – point on Earth’s surface above focus
How Seismographs Work
http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM
the pendulum remains fixed as the ground moves beneath it
Typical Seismogram
http://isu.indstate.edu/jspeer/Earth&Sky/EarthCh11.ppt
Earthquake VocabularySeismology – The study of earthquakes
Seismograph – An instrument that records vibrations in the ground and determines the location and strength of an earthquake
Seismologist – A person who studies earthquakes
Seismic Wave – A wave of energy that travels through the Earth and away from an earthquake in all directions
Seismogram – a tracing of earthquake motion that is created by a seismograph
Primary Waves (P Waves)
• A type of seismic wave that compresses and expands the ground
• The first wave to arrive at a seismograph
http://daphne.meccahosting.com/~a0000e89/insideearth2.htm
Secondary Waves (S Waves)
• A type of seismic wave that moves the ground up and down or side to side
http://daphne.meccahosting.com/~a0000e89/insideearth2.htm
Comparing Seismic Waves
Surface Waves
• Move along the Earth’s surface• Produces motion in the upper crust
– Motion can be up and down– Motion can be around– Motion can be back and forth
• Travel more slowly than S and P waves• More destructive
How do scientists calculate how far a location is from the epicenter of an earthquake?
• Scientists calculate the difference between arrival times of the P waves and S waves
• The further away an earthquake is, the greater the time between the arrival of the P waves and the S waves
Locating Earthquakes
http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM
Locating Earthquakes
http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM
Locating Earthquakes
http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM
How are Earthquakes Measured? Richter Scale
How are Earthquakes Measured? Mercalli Intensity Scale
Click Link for Interactive Demo http://elearning.niu.edu/simulations/images/S_portfolio/Mercalli/Mercalli_Scale.swf
Earthquake Waves & Earth’s Interior
Seismic Waves in the Earth
http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM