Slide Number 1Slide Number 2Slide Number 3Slide Number 4 http://www.youtube.com/watch?v=w3AdFjklR50&feature=related http://www.youtube.com/watch?v=-DSSssHxm4Y&feature=related http://www.youtube.com/watch?v=s8L2kikyVzk Slide Number 6Slide Number 7Slide Number 8Slide Number 9Slide Number 10Measurement of EarthquakesSlide Number 12Measurement of EarthquakesSlide Number 14Slide Number 15Destructive Effects of EarthquakesSlide Number 17Slide Number 18Slide Number 19Slide Number 20Slide Number 21Slide Number 22Slide Number 23Slide Number 24Slide Number 25Elastic Rebound – causes earthquakesElastic ReboundStick-slip FaultsSlide Number 29Slide Number 30Seismic WavesSlide Number 32Slide Number 33Surface WavesSurface WavesDetermining Distance to Point of Energy Release Slide Number 37Slide Number 38Slide Number 39Slide Number 40Slide Number 41MEASUREMENT OF EARTHQUAKESSlide Number 43Measurement (cont.)Slide Number 45Slide Number 46Slide Number 47Slide Number 48Earthquake PredictionSlide Number 50Slide Number 51Slide Number 52Slide Number 53Slide Number 54Slide Number 55Slide Number 56Seismic Character of Earth’s Internal DivisionsSlide Number 58Seismic waves, like light waves, will bend, or refract, when they encounter different material P-wave Shadow Zone S Wave Shadow Zone Slide Number 62Earthquake facts • Earthquakes are caused by a build-up of stress within the crust, causing rocks to fail suddenly. •Some 80 percent of all the planet's earthquakes occur along the Pacific rim. • On average, a magnitude 8 quake strikes somewhere every year. • Most deaths during an earthquake are due to collapsing buildings.•Why earthquakes? Where earthquakes?Distribution of earthquakes with R.S. mag > 5 from 1980-1990. •Why earthquakes? Where earthquakes?•Why earthquakes? Where earthquakes?http://www.youtube.com/watch?v=w3AdFjklR50&feature=related http://www.youtube.com/watch?v=-DSSssHxm4Y&feature=related http://www.youtube.com/watch?v=s8L2kikyVzk Honshu tsunami videosLocating EQsM=9.0 11 March 2011 5:46:23 UTC focus epicenter Locating EQsFaults are where rocks break and move suddenly 30-40 m movement along subduction zone fault in Honshu North American Plate Pacific PlateTsunami (seismic sea wave) caused by seafloor displacement . Tsunamis slow and steepen (up to 30 m) as they enter shallow water.Tsunami wave predictionsMeasurement of Earthquakes • Magnitude -an index of the amount of energy released, proportional to amount of ground motion; -Richter Scale - a logarithmic scale: each number represents >30X more energy and 10X more ground motion than preceding number; examples….Richter magnitude depends on: 1) Separation time (distance) 2) Amplitude (ground shaking)Measurement of Earthquakes • Intensity -based on damage, effects -will vary from place to placeDestructive Effects of Earthquakes • Structural damage from seismic waves- • fire • mass wasting - landslides, liquefaction • tsunami (seismic sea waves)Kobe, Japan, 1995http://environment.nationalgeographic.com/environment/natural-disasters/earthquake-profile.html?fs=video.nationalgeographic.com (National Geographic) http://www.youtube.com/watch?v=SgRry6GZxUo&feature=related(hole in highway) http://www.youtube.com/watch?v=6iNUvlU0SJY (global EQs for 2-month period) http://www.youtube.com/watch?v=reDKxgb_IBQ&feature=related (7.2 quake hits Japan, 2008) http://www.youtube.com/watch?v=7TQDQAesJvM&feature=related (NYC EQ)Types of Stress Plate Tectonics Setting • Confining None • Compressive Convergent • Extensional Divergent • Shear Transform Stress is force concentrated over an area F =100 lbs 10 lbs/ft2 A =10 ft2Strain is the response of a material to stress • Elastic *Rubber ball *Earthquake • Plastic *Modeling clay *Folded rocks • Brittle *Pencil *Faults Type of Strain depends on: • Temperature • Pressure • Material • Timehttp://www.pirate4x4.com/tech/billavista/PR-BV60/Materials/stress strain%201.jpg Plastic flowFolding: plastic response to stress • strain energy used up in folding • no earthquakesFaulting: brittle response to stress •slow or sudden release of small or large amounts of energy •may cause earthquakesElastic Rebound – causes earthquakesElastic ReboundStick-slip Faults • Fault zone may have segments characterized by creep • These may altternate with segments which are stuck (snagged) • As elastic strain accumulates, energy is stored; Subsequently released as large earthquake • Creeping segments store little energy (less dangerous)Stick-slip FaultsSeismic Waves • body waves- move only through earth’s interior; -p wave: primary (compressional) wave, fastest, first to arrive at seismic station; 2.4 – 3.2 miles / second ~10,000 mph compare to F-15 ~0.5 miles / second -s wave: secondary (shear) wave -1.8 – 2.4 miles / second - cannot be transmitted through liquid (ex molten rock)P WAVE (compressional wave)S WAVE (SHEAR WAVE)Surface Waves • move only along the surface; • - slowest wave type • Rayleigh, Love wavesSurface WavesDetermining Distance to Point of Energy Release • Example : thunder and lightning, same source 1) light travels 186,000 miles per sec, instantaneous over 1-25 miles 2) sound travels ~ 1,100 ft per sec Ex. Light-sound time interval of 20 sec indicates lightning was ~ 4 miles awayBasic principles of a seismograph…Record (seismogram) of an earthquake; time separation of arrivals based on wave type. S-P interval shown is ~ 5 minutes. S-P interval Determining EQ EpicenterTravel-time graph, used to determine distance from seismic station to epicenter.The location of an epicenter on the midoceanic ridge in the South Atlantic Ocean. S-P time intervals are used from 3 seismic stations.MEASUREMENT OF EARTHQUAKES • Magnitude -an index of the amount of energy released, proportional to amount of ground motion; -Richter Scale - a logarithmic scale: each number represents >30X more energy and 10X more ground motion than preceding number; examples….Richter magnitude depends on: 1) Separation time (distance) 2) Amplitude (ground shaking)Measurement (cont.) • Intensity - an index of structural damage -based on modified