Earthquakes

Earthquakes Earthquakes – series of shock waves traveling through the earth http://www.youtube.com/watch?v=cavq2HFBa-U 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

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

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).

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

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 https://www.youtube.com/watch?v=chbbiSCczB8

Earthquake Waves Earthquakes – series of shockwaves traveling through the earth

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

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

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

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.

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 https://www.youtube.com/watch?v=ROYOr2WbZdw

10 Things You Didn’t Know About Earthquakes http://www.youtube.com/watch?v=ftZVk0CUWxA Complete corresponding worksheet.