Earthquakes

What is an earthquake? Shaking and trembling that results from the movement of rock beneath Earth’s surface https://www.youtube.com/watch?v=VSgB1IWr6O4

Three Types of Faults Strike-Slip Reverse (FDR) Normal (FUN) Form depending on type of plate motion and complex reaction of earth’s lithospheric blocks Strike-slip Normal Thrust Normal (FUN)

What causes earthquakes? The movement of the plates creates stress (the force that changes a rock’s shape or volume) These stresses (shearing, tension, and compression) work over millions of years to make rocks bend or snap violently.

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 Focus – point inside the Earth where an earthquake begins Epicenter – point on Earth’s surface above focus

How Seismographs Work the pendulum remains fixed as the ground moves beneath it http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM

Typical Seismogram http://isu.indstate.edu/jspeer/Earth&Sky/EarthCh11.ppt

Primary Waves (P Waves) A type of seismic wave that compresses and expands the ground The first wave to arrive at an earthquake 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 Body 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 Most 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

Tsunamis https://www.youtube.com/watch?v=dJBS94GVyuo http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM

Formation of a tsunami http://isu.indstate.edu/jspeer/Earth&Sky/EarthCh11.ppt

Tsunami Warning System http://isu.indstate.edu/jspeer/Earth&Sky/EarthCh11.ppt