Presentation on theme: "Ms. Scott. Scientific study of earthquakes (the seismic waves they generate) It is through this study that we have an understanding of what the interior."— Presentation transcript:
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.
When an earthquake occurs, the energy releases seismic waves that move outward from its focus(center) in all direction
Using a seismographs Sensitive instruments positioned hundreds and and even thousands of kilometers from an earthquake
There are three main kinds of seismic waves P or Primary Waves S or Secondary Waves L or Long( Love) Waves
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)
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
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.
Travel on the surface of the earth and shake the rocks sideways as they progress across the surface
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)