1. Chapter 19

2.  Most Earthquakes are the result of movement in the Earth’s crust at the tectonic plates.  Rocks in the crust resist movement and build up stress overtime.  Stress is the total force acting on crustal rocks per unit of area. When stress is greater than the strength of the rocks, they slip resulting in an earthquake.

3.  Compression: decreases volume of material  Tension: pulls material apart  Shear: twists material  When material is subject to stress it can become deformed; strain.  When rocks break due to stress and strain, it releases massive amounts of energy this usually happens at Faults.

4. PRIMARY WAVESSECONDARY WAVES  Aka P waves  Behave like a compression wave  P waves squeeze and push rocks in the direction the wave is travelling.  Travel fast!  Aka S waves  Behave like a transverse wave  S waves move perpendicular to the direction of the wave  Travel slower.

5.  Surface waves: the slowest type of waves which only travel along the Earth’s surface, not the interior like the S and P body waves.  Surface waves usually cause the most destruction because they move the ground and take the longest time to pass.  The point where the waves originate is where the rock fails; the focus. The point on the crust above this is the epicenter.

6. RICHTER SCALEMERCALLI SCALE  A scale that measures the energy of the largest seismic waves (in magnitude) that are produced during an earthquake.  The numbers are determined by the height or amplitude of the waves.  A wave that measures 8 on the Richter scale is 10 times more energy than a 7.  Measures Earthquakes by how much damage they cause.  See table 19.2 p. 540 in the text.

7.  A large ocean wave generated by vertical motions of the seafloor during an earthquake.  Wave spreads from the epicenter much like the seismic waves.