8.2 measuring earthquakes
DESCRIPTION
8.2 Measuring Earthquakes Earthquake Waves 8.2 Measuring Earthquakes Seismographs are instruments that record earthquake waves. Seismograms are paper records of recorded ground motion made by seismographs.TRANSCRIPT
8.2 Measuring Earthquakes
Earthquake Waves
8.2 Measuring Earthquakes
Seismographs are instruments that record earthquake waves.
Seismograms are paper records of recorded ground motion made by seismographs.
Seismographhttp://www.youtube.com/watch?v=DX5VXGmdnAg
Seismogram
Fastest waves Slowest waves and most destructive
8.2 Measuring Earthquakes
3 kinds of waves• P waves
- Have the greatest velocity of all earthquake waves
- Are push-pull waves that push (compress) and pull (expand) in the direction that the waves travel
- Travel through solids, liquids, and gases
http://www.jclahr.com/science/earth_science/tabletop/pslnkmv.html#
“P waves move through the entire earth- crust, mantle, and core) like a slinky”
Earthquake Waves
8.2 Measuring Earthquakes
• S waves- Seismic waves that travel along Earth’s outer layer
- Slower velocity than P waves
- Shake particles at right angles to the direction that they travel
- Travel only through solids
“S waves move through the ground like a rope”
Seismic Waves Paths Through the Earth
S
SS
P
P
Locating an EarthquakeHow far is your location from the epicenter?
8.2 Measuring Earthquakes
• Distance from you to epicenter is found by the measuring difference in the arrival times between P and S waves.
Locating an Earthquake3 seismographs are required to correctly locate the epicenter of an earthquakeEpicenter is located where three circles intersect
Measuring Earthquakes-
8.2 Measuring Earthquakes
Momentum Magnitude• Moment magnitude is the most widely used
measurement for earthquakes • Estimates the energy released by earthquakes.
• Measures very large earthquakes
Earthquake Magnitudes
Some Notable Earthquakes
Modern Earthquakes
• 7.2 Turkey in 2011 572 deaths• 9.0 Japan in 2011 18000 deathshttp://www.youtube.com/watch?v
=fraPBV4kzvI