1. Earthquakes

2. Earthquakes
Earthquakes – series of shock waves traveling through the earth
Elastic rebound – a movement (slippage) caused by rocks shifting to an unstressed position, when this movement occurs waves of motion in the earth radiate from the point of slippage

3. Earthquakes
Aftershock – secondary earthquakes produces when slippage occurs in one location of the fault it increases strain in another location causing more slippage
Seismologists – earthquake scientists
Seismographs – instruments that detect and measure earthquake waves

4. Earthquakes
Richter Scale – named after Charles Richter. The scale indicates the magnitude of the earthquake. (Ranges from 0 – 9+. Anything over 3 you can feel.)
Magnitude – amount of energy released
Each step up the Richter Scale indicates 31.6 times more energy. (Ex. Magnitude 3 on the Richter Scale has 31.6 times more energy than a magnitude 2).

5. Earthquakes Intensity – earthquake’s destructiveness
Factors of intensity include:
Location underground
Distance
Duration
Structures and population nearby
Focus – center of the earthquake’s activity
Epicenter – the location on the surface that is directly above the focus

6. Earthquake Hazards
Hazard – source of danger, cant do anything about a hazard
Risk – possibility of injury or property damage, reduce risk
Hazards of earthquakes
Buildings failing
Fire – electrical problems
Tsunamis – waves caused by earthquakes
Landslides
Mudslides

7. Earthquake Waves
Earthquakes – series of shockwaves traveling through the earth

8. Earthquake Waves
P Waves – first waves to hit a seismic station, body waves (called P for primus, which means first)
Body waves – waves that can pass through the interior of the earth
Can travel through solid and liquid material
Travel through the earth (mantle, crust, inner and outer core)
Short wavelengths and short amplitude
Wavelength – distance between crests
Amplitude – amount of the earth that is displaced from its resting position

9. Earthquake Waves
S Waves – second waves to hit a seismic station, body waves (called S for secundus which means secondary)
Body waves
Large amplitude
Slower and stronger waves
Travel only through solid material
Do not penetrate core just lithosphere and mantle

10. Earthquake Waves
L Waves – last waves to hit a seismic station, travel along the surface
Slowest of the
earthquake waves
Most destructive
of the earthquake
waves

11. Earthquake Waves
How do we know where the epicenter of an earthquake is?
Length of time between the P and S waves indicates distance from the epicenter. Three seismic stations record the time between the P and S waves. Each station then draws a circle using the station as the center of the circle, and the radius the distance from the epicenter. Where the three circles meet is the epicenter.

12. Predicting Earthquakes
Some earthquakes follow volcanoes
Some volcanoes follow earthquakes
Historical data
Bottom line we cannot predict earthquakes so work on making man made structures more earthquake friendly

13. 10 Things You Didn’t Know About Earthquakes
Complete corresponding worksheet.