Earthquakes Liz LaRosa http://

What is an earthquake? TB pg. 211 Vibrations in the ground that result from movement along breaks in the earth’s lithosphere. Can also be caused by volcanic or magmatic activity

Three Types of Faults, TB pg.213 Strike-Slip - Occurs on a transform boundary Reverse- Occurs on a convergent boundary Normal- Occurs on a divergent boundary

What causes earthquakes? TB pg. 213 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

TB pg. 214 Focus – point inside the Earth where an earthquake begins Epicenter – point on Earth’s surface above focus

How Seismographs or Seismometers Work, TB pg the pendulum remains Video link: cuLJLQground moves beneath it -measures ground motion and can be used to determine the distance seismic waves travel

Typical Seismogram- a graphical illustration of EQ waves

Primary Waves (P Waves) TB pg. 215 A type of seismic wave that compresses and expands the ground The first wave to arrive at an earthquake

Secondary Waves (S Waves) TB pg. 215 A type of seismic wave that moves the ground up and down or side to side

Comparing Seismic Waves

Surface Waves, TB pg. 215 Move along the Earth’s surface Produces motion in the upper crust – Motion can be up and down or rolling motion – 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-use 3 seismic stations Triangulation locates the earthquakes epicenter

Locating Earthquakes

Locating Earthquakes

Locating Earthquakes

How are Earthquakes Measured? 3 Scales are used:  Richter Scale-magnitude-from 0-no limit, amount of ground motion  Moment magnitude-magnitude— total amount of energy in EQ  Modified Mercalli Scale-intensity- measures damage from shaking, I- XII

Richter Scale

How are Earthquakes Measured? Mercalli Intensity Scale Click Link for Interactive Demo

San Francisco Earthquake, 1989 History Channel Video damage.jpg

Earthquake Waves & Earth’s Interior

Earthquake Risk-TB pg. 220

Tsunamis Brain POP-click on pic

Formation of a tsunami

Tsunami Warning System