EARTHQUAKESEARTHQUAKE HAZARDSTSUNAMIGlg 112 1st Edition Exam # 2 Study GuideEARTHQUAKES -Where do earthquakes occur? They occur on faults, not just on plate boundaries. -What is an earthquake? It is a vibration of the earth caused by a rapid release of energy. -What causes earthquakes? The main cause you need to know is faults. However, they also occur from volcanoes, extra-terrestrial impacts, humans (drills for example), bomb explosions, and landslides. -Elastic Rebound 1. stress must be applied2. strain energy accumulates (deformation) 3. rock breaks (stored energy is released)4. energy released  seismic waves -Focus: the center of the fault that breaks underground-Epicenter: the center of the earthquake at earth’s surface-Fault scarp: land that jumps up in an earthquake-Foreshocks: small magnitude earth shaking before the main quake-Main Shock: the biggest magnitude earth shaking in a quake -Aftershocks: the smaller shakes that occur after the main shock -Seismic Waves -Body Waves (for both you should know: relative speed, type of motion (which one(s) travel through solids or liquids?, what do we feel?) These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.-Primary (P) waves Speed: approx. 4mi/second Movement: push/pull movement. Vibrates in travel direction. Compressional waves. They DO travel through liquids What we feel: a sharp vertical jolt -Secondary (S) waves Speed: approx.. 2mi/sec.Movement: side to side. Vibrate perpendicular to travel direction. Shear waves.What we feel: side to side motion-Surface Waves Last to arriveLots of different motionMost destructive-Seismograph: an older version of the seismometer. Measured the shaking with a pen and weight.-Seismometer: a computer version of the seismograph. The computer just tells the pen what to write -Seismogram: the written record that comes from the seismometer. You read it from left to right. The time is also recorded at the first sign of each wave. P waves are the first lines you see. S waves are the wavy lines in the middle that are bigger. Surface waves are the last lines that are even bigger. (know how to interpret a seismogram: P- and S-wave arrivals, distance from epicenter) The epicenter is calculated by the time difference between the P and S waves. -Magnitude (quantitative)(each magnitude number is equivalent to 10x more shaking & 32x more energy released) -Richter Scale -How is the Richter Scale Magnitude of an earthquake determined?a. the P and S wave arrival timeb. amplitude of greatest shakingIt is based on only the amount of shaking. Each increase is 10x more shaking -Moment Magnitude-how is the Moment Magnitude of an earthquake calculated? a. size of the faultb. amount of slipc. rock strengthThis scale is based on energy release instead of shaking. Therefore it is more efficient. `Each scale increase is 32x more energy. -Highest magnitude earthquake ever recorded?  1960 Chile M 9.5 -Intensity (qualitative) -Modified Mercalli Intensity Scale -how is it determined?It is determined by what we feel at the surface. It is numbered I-XII with XII being the most intense shaking -what is it based on? What humans feel -Factors controlling the intensity of ground shaking? -ground composition-distance from the epicenter-depth of the focus-directivity of the fault-magnitude EARTHQUAKE HAZARDS (know what each of these are, what causes them, why it is a hazard, and examples) -Ground Shaking-What hazards are associated with ground shaking? -What types of building materials don’t do well in earthquakes? What materials tend to crumble? Overhangs and other things attached to the building tend to fall in earthquakes. That is why running in or outside is a bad idea. Something could fall on you in the process. -What to do during an earthquake… …if you’re inside? Stay inside. Get under something (drop-cover-hold). If you are in bed stay in bed …if you’re outside? Stay outside. Get to an open area …if you’re in a car? Pull over to a safe spot and stay in it -What room in the house is most dangerous? The kitchen-Liquefaction -What is it? wet sediments become quicksand. It makes the ground soft-How/why does it happen? Unconsolidated wet sediments lose frictional contact and become a dense fluid. -Landslides Example: 1964 Good Friday Alaska Earthquake (M 9.2) This landslide destroyed a whole neighborhood (Turnagin Heights) and instead of rebuilding (because that would be stupid) they made it “Earthquake Park” as a reminder of what happened. -Floods -What causes flooding?Landslides into a river (upstream flooding)Water mains breakLand surface/elevation changeDam/levy break (downstream flooding)Tsunami -Where does it happen?-Example: Quake Lakes in China These were caused by a landslide into a river. The earthquake was a magnitude 8.0. It was in Sichuan Province on May 12, 2008-Fires -Why do they happen?Gas lines breakElectrical lines breakOvens/stoves/candles move/fall overLots of fuel/debrisFriction- sparksElectrical sparksMatches, lighters, etc-why do they burn so long? Blocked/destroyed roadsEmergency response disrupted/delayed and overwhelmedFuel availableArsonists Water mains broken --- means no water to put out firesBig fire – takes lots of time/energy and priority over the smaller fires -Example: 1906 San Francisco Earthquake/FireLasted 3 days and caused 80% damage-Disease Outbreak -Why? What leads to this? Contaminated waterLots of people in close quartersLack of sanitationSewers breaking/leakingCut infectionsHospitals are busy so some people don’t go and become worseRodents Radiation EXAMPLE: valley fever could come from lose dirt and bacteria getting into the air when the ground shakes in southern California. TSUNAMI -VIDEO: Japan’s Killer Quake -causes (how do they form?) Volcanic eruptionsAsteroid impactsLandslides Earthquakes (subduction zones) must have:-underwater-vertical seafloor movement-large magnitude -wave characteristics (in the deep ocean and near shore) Speed is controlled by water depthDeep ocean Shallow waterSpeed 450 mph 30 mphWavelength 60 miles 4 milesAmplitude 3 ft <100 ft -what does a tsunami look like? Wall of waterRapid increaseNot surfable More than one waveCan last for hours or days evenThe first wave is not always the biggest -how far do they travel? …in the deep ocean? Across the oceansDirection