Earthquakes and Seismic WavesQuestions to ponderMeasuring earthquakesMercalli ScaleMercalli Intensity maps 1886 Charleston, SC 1811 New Madrid, MORichter ScalePowerPoint PresentationRelationship of Richter Magnitude with Released energySlide 9Slide 10Slide 11Earthquake hazards – ground displacementEarthquake hazards - landslidesEarthquake hazards - liquefactionSlide 15Slide 16Earthquake hazards - firesEarthquake hazardsSlide 19Slide 20Slide 21Earthquake hazards - tsunamisSlide 23Slide 24Hawaii, 1946Tsunami Travel Path and Time from 1960 Chile, M 9.2 ‘quakeSlide 27Slide 28Tsunami waves encircled the globe from the 2004 seismic eventJapan 2011 M 9Slide 31Slide 32Untold damagesSlide 34Reducing the Risk from earthquakesSeismic RiskSlide 37Building designEducationCan we prevent (or cause) Earthquakes?Predicting earthquakesChanges in landformsUsing GPS and Laser monitoring to observe changes in the ground surfaceOther precursorsSeismic Gaps – sections along a fault line that have not experience any recent seismic activityAnimal BehaviorPlate tectonics & SeismicitySlide 48Slide 49Earth’s interiorThe behavior of seismic body wavesThe behavior of seismic body wavesSlide 53Slide 54Earthquakes and Earthquakes and Seismic WavesSeismic WavesLecture 23Questions to ponder•How do we measure earthquakes? What systems do we use and how do they differ?•What are the hazards from earthquakes? How does the type of material affect the hazards we can expect?•How do we predict and monitor for earthquakes?Measuring earthquakes•2 Systems are used•Mercalli Scale–Measures Intensity of shaking by assessing the damages–Scale from I to XII•Richter Scale–Measures Magnitude of energy released–Scale from 1 - 10Mercalli ScaleMercalli Intensity maps 1886 Charleston, SC 1811 New Madrid, MORichter Scale•Measures the magnitude of energy•It is a Log scale system•Each 1 whole unit represents a 10-fold increase in Magnitude, but a 30-fold increase in the amount of Energy released for each whole unit increase!•Magnitude, then, is based upon the amplitude of the seismic waveMagnitude = Log (X/T) + (S-P interval)X = Maximum Amplitude (height) of waveT = the Duration of 1 oscillationRelationship of Richter Magnitudewith Released energy•An earthquake of M 7M 7 has 1010 times the amplitude of an earthquake of M 6M 6, and 3030 times more energy•An earthquake of M 7M 7 has 100100 times the amplitude of an earthquake of M 5M 5, and ?? times more energy•An earthquake of M 7M 7 has ?? times the amplitude of an earthquake of M 4M 4, and ?? times more energyEarthquake Hazards•Earthquakes pose a significant factor killing thousands each year–Primary effect is ground motion–Ground motion may cause additional indirect damage by•Displacement•Landslides•Liquefaction of soil•Fires from broken gas pipes•TsunamisEarthquake Hazards•Earthquakes pose a significant factor killing thousands each year–Primary effect is ground motion–Ground motion may cause additional indirect damage by•Displacement•Landslides•Liquefaction of soil•Fires from broken gas pipes•TsunamisEarthquake hazards – ground displacement39 feet ofVertical upliftEarthquake hazards - landslides1920 1920 ‘‘quake in SW China:quake in SW China:180,000 died as a result 180,000 died as a result of landslides associated of landslides associated with the earthquakewith the earthquakeEarthquake hazards - liquefactionUnconsolidated sediments can behave as a liquid when seismic waves passAlaska (Turnagin Heights) from 1964Niigata, Japan, Liquefaction from1964 earthquakeEarthquake hazards - fires1906 San Francisco Earthquake1906 San Francisco EarthquakeEarthquake hazards•Most occur from the collapse of our “world” – buildings and structures•In some less developed countries, disease and famine affect many after earthquakeHaiti 2010200,000 deadMost were buried, nameless in mass gracesHaitiEarthquake hazards - tsunamis•Large Amplitude and long wave-length ocean waves caused by displacement of water•Can reach heights of 100 feet; Can travel at velocities of 500 mph!•Seafloor fault movement•2004 Sumatran Earthquake ~ 280,000 killedHawaii, 1946Tsunami Travel Path and Time from 1960 Chile, M 9.2 ‘quakeBanda Aceh, IndonesiaBefore and After TsunamiTsunami waves encircled the globe from the2004 seismic eventJapan 2011M 9Eurasian plateUntold damages•Land and building failure•Nuclear reactor damage and radioactive issues•Contamination•Debris field moving across PacificReducing the Risk from earthquakes•Knowledge and planning is they key•Know the risk of your area•Create and enforce applicable building codesSeismic RiskBuilding designDesign structures that move with ground motionEducationCan we prevent (or cause) Earthquakes?Predicting earthquakes•Seismic Risk maps•Changes in land forms•Seismic Gaps•Fluctuations of water table•Released gases•Animal BehaviorChanges in landforms•Tilting•Dilancy of rocks (expansion and fractures)Using GPS and Laser monitoring to observe changes in the ground surfaceOther precursors•Water table elevation in water wells may fluctuate•Different dissolved gases may be released into groundwater•Therefore, groundwater monitoring may also help predict earthquakesSeismic Gaps – sections along a fault line that have not experience any recent seismic activityAnimal Behavior•Many animals sense an impending earthquake•We are not certain why they flee•Many examples of such behaviorPlate tectonics & SeismicityEarth’s interior•Already know that seismic activity ceases about 450 miles (~ 700 km) in depth•Therefore, we know also, that the rocks must become partially molten around this point•Seismic waves also provide information about the material they travel throughThe behavior of seismic body wavesFaster than S-waves Slower than P-wavesP wavesS wavesTravel through solids, Travel only through solids liquids, and gases (faster through solids, slower through liquids)The behavior of seismic body wavesWaves can Refract (Bend)when travellingThrough different layersWaves can Reflect when they encounter another layer of materialVelocity of Seismic waves increases with increasing densityVelocityDensityVelocity also Decreases when materials increase in temperatureThe behavior of seismic body wavesP Wave Velocity changes; S Waves cease at ~ 3000