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HS Earth Science - Earthquakes Unit

HS Earth Science - Earthquakes Unit

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  • Elastic- material is compressed bent or stretched and material will return to original form after stress is removed <br /> Plastic – permanent deformation <br />
  • Safer in a field than a building <br />
  • Many buildings not made to withstand EQ <br /> Type of ground underneath effects the building above in a EQ <br />

Earthquakes Earthquakes Presentation Transcript

  • Earthquakes Outline 1Earthquakes and Plate Tectonics 2Types of Seismic Waves Recording Earthquakes Measuring Earthquakes Locating an Earthquake 3Destruction to Buildings and Properties Tsunamis Earthquake Safety Earthquake Warnings and Predictions
  • 1
  • Earthquakes are vibrations in the earth’s crust The movement between plate and along faults is not smooth They move in jerks, giving rise to earthquakes. The locations of earthquakes throughout the world exist along the major tectonic boundaries. An earthquake is a sudden shaking of the ground. They generate seismic waves.
  • Stress and Strain • stress – total force acting on crustal rocks per unit area • strain – deformation of materials in response to stress • elastic deformation • plastic deformation
  • Earthquake Vocab • Focus • Epicenter • Fault
  • Focus – Area where slippage first occurs
  • Earthquakes create seismic waves which shake the ground as they pass. Earthquakes create waves just like waves of water moving across the ocean.
  • Consider what happens when a drop of rain hits a pond of water. The drop disturbs the flat surface of the water and creates waves that travel outward in all directions from the disturbance. These waves travel on the surface of the pond, along the interface between the water and the air.
  • FAULTS Distant forces cause a gradual build up of stress in the earth over tens or hundreds or thousands of years, slowly distorting the earth underneath our feet. Eventually, a pre-existing weakness in the earth--called a fault or a fault zone--can not resist the strain any longer and fails catastrophically. San Andreas Fault
  • Stresses
  • Connection to Plate Tectonics • What type of boundary causes tension? • divergent • What type of boundary causes compression? • convergent • What type of boundary causes shear? • transform
  • Mid-Ocean Ridges This is a map of the major oceanic spreading centers.
  • Types of Faults Reverse (convergent) • Compression causes horizontal and vertical movement • Where might this occur (real-world example)? Normal (divergent) • Tension causes horizontal and vertical movement Where might this occur (real-world example)?
  • Types of Faults Strike-slip (transform) • Shear causes horizontal movement • Where might this occur (real-world example)?
  • Fault Zones Faults are narrow zones in the Earth, usually extending no more than about 10 miles deep, which separate rigid crustal blocks. A well known fault is the San Andreas Fault which separates the Pacific plate from the North American plate.
  • California Faults • http://www.pbslearningmedia.org/resource/ess
  • The Pacific plate is moving to the northwest at a rate of about 4 inches per year.
  • 2 • Types of Seismic Waves • Recording Earthquakes • Locating Earthquakes
  • Types of Seismic Waves Earthquakes generate three major types of seismic waves P, for "Primary" S, for "Secondary" waves L, for “Long” waves
  • P Waves - Primary Move the fastest and are the first recorded by a seismographic Can travel through liquids and solids The P waves move in a compressional motion similar to the motion of a slinky
  • S Waves - Secondary Secondary Waves are the second to be recorded by a seismograph, Can only travel through solid materials S waves move in a shear motion perpendicular to the direction the wave is traveling.
  • L Waves – Long Waves or Surface Waves Surface or L waves occur only in the earth's crust and cause the most damage travel along the surface of the earth from the point directly above the quake or epicenter Slowest moving waves, last to be recorded by a seismograph.
  • Recording Earthquakes An earthquake is a sudden shaking of the ground. They generate seismic waves which can be recorded on a sensitive instrument called a seismograph.
  • Advances in seismograph technology have increased our understanding of both earthquakes and the Earth itself.
  • Perhaps the earliest seismograph was invented in China A.D. 136 by a man named Choko.
  • The Seismograph • http://www.pbslearningmedia.org/resource/ess
  • Earthquake Measurement Richter Scale expresses the magnitude or measure of energy released by an earthquake. Mercalli scale expresses the intensity of an earthquake or the amount of damage it causes.
  • I. Instrumental II. Feeble III. Slight IV. Moderate V. Rather strong VI. Strong VII. Very strong VIII. Destructive IX. Ruinous X.Disastrous Detected only by seismographs Noticed only by sensitive people. Resembling vibrations caused by heavy traffic. Felt by people walking; rocking of free standing objects. Sleepers awakened and bells ring. Trees sway, some damage from overturning and falling objects. General alarm, cracking of walls. Chimneys fall and there is some damage to buildings. Ground begins to crack, houses begin to collapse and pipes break. Ground badly cracked and many buildings are destroyed. There are some landslides. XI.Very Disastrous Few buildings remain standing; bridges and railways destroyed; water, gas, electricity and telephones out of action. XII.Catastrophic Total destruction; objects are thrown into the air, much heaving, shaking and distortion of the ground. The Modified Mercalli Scale
  • Richter Scale Magnitude 2.5 or less 2.5 to 5.4 5.5 to 6.0 6.1 to 6.9 7.0 to 7.9 8.0 or greater Earthquake Effects Usually not felt, but can be recorded by seismograph. Often felt, but only causes minor damage. Slight damage to buildings and other structures. May cause a lot of damage in very populated areas. Major earthquake. Serious damage. Great earthquake. Can totally destroy communities near the epicenter. The Richter magnitudes are based on a logarithmic scale (base 10). What this means is that for each whole number you go up on the Richter scale, the energy released by the earthquake goes up ten times
  • Richter Magnitude How many kilograms of TNT would have this much energy? 0 1.0 2.0 3.0 0.6 20 600 20 000 4.0 60 000 5.0 20 000 000 6.0 60 000 000 7.0 20 billion 8.0 60 billion 9.0 20 trillion * * * * * * * * * * * * * * Smallest quake people can normally feel Most people near epicenter feel the quake Nearly 100, 000 occur every year of size 2.5 - 3.0 A small fission atomic bomb Quakes above 4.5 can cause local damage A standard fission bomb, similar to the first bomb tested in New Mexico, U.S. A hydrogen bomb; can cause great damage locally About 100 shallow quakes of size 6.0 every year Major earthquake; about 14 every year Enough energy to heat New York City for 1 year Large enough to be detected all over globe Largest known: 8.9 in Japan and in Chile/Ecuador San Francisco destroyed by 8.25 in 1906 Roughly the world’s energy usage in a year
  • Locating an Earthquake The point beneath the Earth's surface where the rocks break and move is called the focus. The focus is the underground point of origin of an earthquake. Directly above the focus, on the Earth's surface, is the epicenter. Earthquake waves reach the epicenter first. The most violent shaking is found at the epicenter.
  • Epicenter Focus
  • Scientist must have information from three seismographic stations at different locations to plot the epicenter of an earthquake
  • Need readings from three seismic centers to locate epicenter. The epicenter is the point at which the circles intersect.
  • Three Major Earthquake Zones Pacific Ring of Fire
  • New Madrid Earthquake December of 1811, the largest earthquake ever recorded in American History started. This earthquake, called the New Madrid Earthquake because of its primary location on the New Madrid Fault, near New Madrid, Missouri. From the effects of the 1811-1812 earthquakes, it can be estimated that they had a magnitude of 8.0 or higher on the not yet invented Richter scale. Large areas sank into the earth, new lakes were formed, and the Mississippi River changed its course due to the earthquakes.
  • Review 1. What instrument is used to record seismic waves? 2. Explain the three types of seismic waves. 3. How is the epicenter of an earthquake located? 4. How do scientist measure the magnitude of an earthquake?
  • Earthquake Damage Earthquakes are among the most powerful events on earth, and their results can be terrifying.
  • 3 • Destruction to Buildings and Properties Tsunamis Earthquake Safety Earthquake Warnings and Predictions
  • Earthquake Destruction important factors: Intensity & duration of shaking Soil type (soft? hard rock?) Building design
  • 1964 Valdez, Alaska • http://www.pbslearningmedia.org/resource/ean
  • Tsunami damage: Alaska 1964 earthquake
  • Intensity One way of describing the size of an earthquake is by the amount of shaking at some particular location.
  • Duration Length of time the earthquake lasts.
  • other effects Liquifaction Liquefaction essentially means that the soil is turned into liquid. The liquified solid then flows and causes severe damage to buildings and infrastructure
  • Liquifaction Water-saturated, well sorted, fine grain sands and silts behave as fluids rather than solids.
  • other effects A tsunami (pronounced tsoo-nah-mee) is a wave train, or series of waves, generated in a body of water by an impulsive disturbance that vertically displaces the water column. Tsunamis
  • Tsunami is a Big Wave Tsunami from Chile earthquake 1960 Magnitude 9.5
  • Tsunami damage in Hawaii : From 1960 Chile earthquake, 15 hours later
  • Earthquake Safety Stocking up now on emergency supplies can add to your safety and comfort during and after an earthquake. Store enough supplies for at least 72 hours.
  • Water: 1 gallon per person per day (a week's supply of water is preferable) Water purification kit First aid kit, freshly stocked First aid book Food Can opener (non-electric) Blankets or sleeping bags Portable radio, flashlight and spare batteries Essential medication Extra pair of eyeglasses Extra pair of house and car keys Fire extinguisher : A-B-C type Food, water and restraint (leash or carrier) for pets Cash and change Baby supplies: formula, bottle, pacifier, soap and baby powder, clothing, blankets, baby wipes, disposable diapers, canned food and juices.
  • Stay Calm If You Are Indoors Protect yourself from falling debris by standing in a doorway or crouching under a desk or table.
  • If You Are In An Automobile Stay away from power lines, tunnels, tall buildings, and bridges, and stay in car until the tremors cease.
  • After an earthquake be cautious Check for fire and fire hazards. Watch for broken glass Avoid downed power lines
  • Earthquake Warnings and Predictions Earliest means of prediction was animal behavior Using records of past earthquakes
  • Scientists are trying to make more accurate predictions by detecting changes in the earth’s crust. Faults have been located and mapped Instruments placed along faults measure small changes in rock movement.
  • Seismic Gaps – Zones of immobile rock along faults Scientists think that seismic gaps, where the fault is locked and unable to move, are the locations of future earthquakes
  • Other Warnings Slight tilting of the ground Detect strain and cracks caused by stress Change in magnetic and electrical properties of rock Detect natural gas seepage Local P waves slow down
  • Tests at Rangely, Colorado Injected water along a fault which reduced friction and the earthquakes were less severe
  • Forecasting EQ’s • http://www.pbslearningmedia.org/resource/nvs
  • Section 6:3 Review 1. How do tall buildings usually respond during a major earthquake? 2. What causes tsunamis? 3. What should you do if an earthquake strikes while you are at home? In a car? 4. What are some early warning signs of earthquake activity? 5. What type of building construction and location regulations should be included in the building code of a city located near an active fault?