1. Ms. Scott

2.  Scientific study of earthquakes (the seismic waves they generate)  It is through this study that we have an understanding of what the interior of the Earth is comprised of.

3.  When an earthquake occurs, the energy releases seismic waves that move outward from its focus(center) in all direction

4.  Using a seismographs  Sensitive instruments positioned hundreds and and even thousands of kilometers from an earthquake

5.  There are three main kinds of seismic waves  P or Primary Waves  S or Secondary Waves  L or Long( Love) Waves

6.  P waves are the fastest of the waves  Penetrate the earth’s interior.  Compressional waves since they alternatively push (compress) and pull (dilate) the rocks through which they pass  Can pass through both solid and liquid  Can be detected far away from the focus  Which leads scientist to believe that the core is in a liquid (or semi-liquid state)

7.  S waves are slower, transverse waves that travel through the rock by moving it from side to side (shearing the rock)  Due to this action this wave can only travel through solid formations

9.  On page 62 (figure 4.11)  Shows how seismic waves are bent, or refracted as the move across the boundaries between the layers with differing density This bending creates two shadow zones where there are no P or S waves detected.

11.  Travel on the surface of the earth and shake the rocks sideways as they progress across the surface

12.  The distance from the seismic station to the earthquake’s epicenter (the point on the earth’s surface directly above the focus) can be determined  The actual location of the earthquake can be plotted on a map using distance calculation from at least 3 different seismic stations.  Scientists use the seismic information to determine the nature of the interior of earth  The speed of the seismic eaves gives an indication of the density (the denser the material the faster the waves can travel)