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Earthquake PPT.ppt
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- 2. Assessing Prior Knowledge andRelativity • What have you heard about earthquakes lately? • Why should we study earthquakes?
- 3. Falcon Focus • 8-1.1The standard metric unit of length used in a science lab is… • a. Celsius • b. Gram • c. Liter • d. Meter
- 4. Essential Question • WHATCAUSES EARTHQUAKES AND WHERE DO THEY HAPPEN?
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- 7. The earthquake thatcaused the most destruction in history occurred in the Shansi province of China on January 23,1556. An estimated 830,000 people were killed. The second most destructive earthquake also occurred in China--in July, 1976--and killed 255,000 people.
- 8. The definition ofan earthquake is… vibrations that cause the breaking of rocks. These vibrations move in all directions through the earth. They begin at a point along a fault.
- 9. Earthquakes • Forces___ and__Stresses__ (8-3.7– tension, compression, and shearing) along faults can build up as blocks of rock are pushed (compression or shearing) or pulled apart (tension). If the __pressure___ or stress becomes too great, the rock breaks at a weak point along the fault and ___energy_____ is released
- 10. Earthquakes • ____Earthquakes_____ arevibrations produced when rocks break along a ___fault_____. The term earthquake describes the sudden slip on a fault and includes the ground shaking and radiating _____seismic waves___ that is caused by the slip. ___Volcanic Activity____, or other geologic processes, may cause stress changes in the earth that can also result in an earthquake.
- 11. The earth’s crustis constantly experiencing pressure from forces within and around it. This pressure builds up over time, and eventually causes the crust to break. This becomes a fault. Let’s experience it…
- 12. Faults are dividedinto three main groups: Normal fault - when two plates are moving apart and one side of the fracture moves below the other; (caused by tension forces!) Reverse fault - when two plates collide and one side of the fracture moves on top of another; (caused by compression forces!!) Strike-slip - when two plates slide past each other. (caused by shear forces!)
- 13. Three Types ofFaults Strike-Slip Reverse Normal
- 14. An earthquake beginsalong a fault (a crack in the earth’s surface) at a point called the focus. Directly above the focus is a point on the earth’s surface called the epicenter.
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- 16. Seismologists have stationsall over the world that continuously collect information about earthquakes. This kind of information can help scientists figure out where larger, more destructive earthquakes may strike by mapping out the location of smaller ‘quakes. They also get a greater understanding of the changes the earth’s crust makes as the earthquakes occur. How do they do this???
- 17. When the faultruptures with a sudden movement energy is released that has built up over the years. This energy is released in the form of vibrations called 'seismic waves'… earthquakes! It is actually when these seismic waves reach the surface of the earth that most of the destruction occurs, which we associate with earthquakes.
- 18. Parts of theEarthquake • The energy spreads outward in all directions as vibrations called ____seismic waves_____. • The _focus____ of the earthquake is the point in the crust, or mantle, where energy is released. • The _epicenter___ is the point on Earth’s surface directly above the focus; energy that reaches the surface is greatest at this point.
- 19. Focus – pointinside the Earth where an earthquake begins Epicenter – point on Earth’s surface above focus
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- 21. WHAT CAUSES EARTHQUAKES? •Used to describe both sudden slip on a fault, and the resulting ground shaking and radiated seismic energy caused by the slip • Caused by volcanic or magmatic activity, • Caused by other sudden stress changes in the earth.
- 22. What causes earthquakes? •Tectonic plates move past each other causing stress. Stress causes the rock to deform
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- 24. Cause of Earthquakes WhatCauses an Earthquake? • An aftershock is a small earthquake that follows the main earthquake. • A foreshock is a small earthquake that often precedes a major earthquake. Aftershocks and Foreshocks
- 25. Earthquakes can alsocause landslides, sudden eruptions as in the case of a hot lava flow from a volcano or giant waves called tsunamis. Sometimes new land mass are also formed. Such earthquakes are attributed with the creation of the greatest undersea mountain range and the longest land mountain range.
- 26. Landslides & Tsunamis •http://video.nationalgeographic.com/video/1 01-videos/landslides • http://video.nationalgeographic.com/video/1 01-videos/tsunami-101
- 33. QuickTime™ and a GIFdecompressor are needed to see this picture. …And that was just a 7.2 on the Richter scale!
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- 38. Parkfield, CA “Earthquake Capitalof the World” Earthquake Hazard Potential Map
- 39. Where Do EarthquakesOccur and How Often? ~80% of all earthquakes occur in the circum-Pacific belt – most of these result from convergent margin activity – ~15% occur in the Mediterranean-Asiatic belt – remaining 5% occur in the interiors of plates and on spreading ridge centers – more than 150,000 quakes strong enough to be felt are recorded each year
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- 41. Focus and Epicenterof Earthquake
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- 43. FALCON FOCUS • THEPOINT ON EARTH’S SURFACE WHERE THE GREATEST ENERGY FROM THE EARTHQUAKE IS RELEASED IS ___________. A. THE EPICENTER B. THE FOCUS C. THE ASTHENOSPHERE D. THE FAULT
- 44. FALCON FOCUS • THEPOINT ON EARTH’S SURFACE WHERE THE GREATEST ENERGY FROM THE EARTHQUAKE IS RELEASED IS ___________. A. THE EPICENTER B. THE FOCUS C. THE ASTHENOSPHERE D. THE FAULT
- 45. ESSENTIAL QUESTION • HOWWOULD YOU COMPARE AND CONSTRAST THE THREEE TYPES OF SEISMIC WAVES?
- 46. INTRODUCTION • IN APOP AND LOCK DANCE MOVE, STUDENTS WILL DEMONSTRATE THE 3 TYPES OF SEISMIC WAVES
- 47. SEISMIC WAVES • _SEISMICWAVES___ are waves generated by an earthquake that travel through the Earth. These waves can cause the ground to move forward, backward, up, down, and even to ripple. Seismic Waves are generated at the __SAME___ time but move in different ways, and at different speeds.
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- 49. 3 TYPES OFSEISMIC WAVES • PRIMARY (P) WAVES • SECONDARY (S) WAVES • SURFACE WAVES CONSIDERED AS BODY WAVES
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- 51. Earthquake Waves 8.2 MeasuringEarthquakes Body Waves • P waves • Identified as P waves or S 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
- 52. PRIMARY (P) WAVE •Move out from the earthquake focus, the point where the energy is released • Travel the fastest of the three waves • Move through solid and liquid layers of Earth (it also can move in gas) • Push and pull rock creating a back-and- forth motion in the direction the wave is moving (longitudinal wave)
- 53. Primary Waves (PWaves) • A type of seismic wave that compresses and expands the ground • The first wave to arrive at an earthquake http://daphne.meccahosting.com/~a0000e89/insideearth2.htm
- 54. Earthquake Waves 8.2 MeasuringEarthquakes Body Waves • 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 A seismogram shows all three types of seismic waves—surface waves, P waves, and S waves.
- 55. Secondary Waves (SWaves) • Move out from the earthquake focus • Move slower than primary waves • Can only move through solid rock • Move at right angles to primary waves causing rocks to move up and down and side to side (transverse wave)
- 56. Secondary Waves (SWaves) • A type of seismic wave that moves the ground up and down or side to side http://daphne.meccahosting.com/~a0000e89/insideearth2.htm
- 57. Body Waves: Pand S waves • Body waves – P or primary waves • fastest waves – travel through solids, liquids, or gases • compressional wave, material movement is in the same direction as wave movement – S or secondary waves • slower than P waves • travel through solids only • shear waves - move material perpendicular to wave movement
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- 60. SURFACE WAVES • Formwhen P and S waves reach the surface • Can cause the ground to shake making rock sway from side to side and roll like an ocean wave • These waves cause the most destruction • They move back and forth and in a rolling motion along the surface • They release all of the energy of the earthquake
- 61. Surface Waves: Rand L waves • Surface Waves – Travel just below or along the ground’s surface – Slower than body waves; rolling and side-to-side movement – Especially damaging to buildings
- 62. Surface Waves • Movealong the Earth’s surface • Produces motion in the upper crust – Motion can be up and down – Motion can be around – Motion can be back and forth • Travel more slowly than S and P waves • More destructive
- 64. Seismic Waves PathsThrough the Earth
- 65. Earth’s Interior Showing Pand S Wave Paths
- 66. • Scientists usethe principle that the speed and direction of a seismic wave depends on the material it travels through. Because of the behavior of these different waves, scientists have indirect evidence for the solid inner core and liquid outer core of Earth; because earthquake waves travel faster through the mantle than through the crust, scientists know that the mantle is denser than the crust.
- 67. Earthquake Waves &Earth’s Interior
- 68. ACTIVITY • CREATE S,P, AND SURFACE WAVES USING A STRING AND A SLINKY
- 69. Primary or “P” Wave Secondary or“S” Wave
- 70. Measuring Earthquakes • Themovement of materials in the __outer_ core (which is a liquid) of the Earth is inferred to be the cause of Earth’s _magnetic field___. A compass needle will align with the lines of force of Earth’s magnetic field. __Iron__ and _Nickel__ are metals that easily magnetize, and are inferred to be the metals in Earth’s core.
- 71. Measuring Earthquakes • Theenergy spreads outward in all directions as vibrations called ___Seismic Waves____. Seismic waves can be measured and recorded by a ____seismograph_______. • __Seismographs______ are instruments or a device that detects and records seismic or earthquake waves. It measures the vertical ground motion and the horizontal ground motions (N-S/E- W). It also traces wave shapes onto paper and translates waves into an electronic signal.
- 72. Measuring Earthquakes • Thevibration record, called a seismogram, looks like jagged lines on paper. Seismograms are traces of amplified, electronically recorded ground motion made by seismographs. • Measuring the time between the arrival of the P and S waves determines the distance between the recording seismograph and the earthquake epicenter.
- 73. Earthquake Waves Measuring Earthquakes Seismographs are instruments that record earthquake waves. Seismograms are traces of amplified, electronically recorded ground motion made by seismographs.
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- 78. How is anEarthquake’s Epicenter Located? Seismic wave behavior – P waves arrive first, then S waves, then L and R – Average speeds for all these waves is known – After an earthquake, the difference in arrival times at a seismograph station can be used to calculate the distance from the seismograph to the epicenter.
- 79. Determining the locationof an earthquake First, distance to earthquake is determined. 1. Seismographs record seismic waves 2. From seismograph record called the seismogram, measure time delay between P & S wave arrival 3. Use travel time curve to determine distance to earthquake as function of P-S time delay Now we know distance waves traveled, but we don't know the direction from which they came. We must repeat the activity for each of at least three (3) stations to triangulate a point (epicenter of quake). Plot a circle around seismograph location; radius of circle is the distance to the quake. Quake occurred somewhere along that circle. Do the same thing for at least 3 seismograph stations; circles intersect at epicenter. Thus, point is triangulated and epicenter is located.
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- 81. How is anEarthquake’s Epicenter Located? Time-distance graph showing the average travel times for P- and S- waves. The farther away a seismograph is from the focus of an earthquake, the longer the interval between the arrivals of the P- and S- waves
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- 83. How is anEarthquake’s Epicenter Located? • Three seismograph stations are needed to locate the epicenter of an earthquake • A circle where the radius equals the distance to the epicenter is drawn • The intersection of the circles locates the epicenter
- 84. Locating an EarthquakeEpicenter • Triangulate means to use three positions to determine an exact location.
- 85. What is Triangulation? •Triangulation identifies the epicenter of an earthquake. The location of an earthquake’s epicenter is found by plotting circles on a map from the records of three seismograph stations and finding the point where the three circles intersect. Triangulation is the process of determining the location of a point by measuring angles to it from known points at either end of a fixed baseline, rather than measuring distances to the point directly.
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- 89. Triangulation of 3 stations tolocate earthquake epicenter
- 90. How do scientistscalculate how far a location is from the epicenter of an earthquake? • Scientists calculate the difference between arrival times of the P waves and S waves • The further away an earthquake is, the greater the time between the arrival of the P waves and the S waves
- 91. Earthquakes are measuredusing the Richter Scale. The strongest earthquake ever measured was a 9.5 on the Richter Scale. This is a measurement of the amount of energy released from the earthquake.
- 92. Measuring Earthquakes 8.2 MeasuringEarthquakes Historically, scientists have used two different types of measurements to describe the size of an earthquake —intensity and magnitude. Richter Scale • The _Richter Scale expresses the magnitude of an Earthquake and measures the energy released. The scale goes from 1 to 10 . • Based on the amplitude of the largest seismic wave
- 93. How are theSize and Strength of an Earthquake Measured? • Magnitude – Richter scale measures total amount of energy released by an earthquake; independent of intensity – Amplitude of the largest wave produced by an event is corrected for distance and assigned a value on an open-ended logarithmic scale
- 94. Determining the magnitudeof an earthquake Magnitude -- measure of energy released during earthquake. There are several different ways to measure magnitude. Most common magnitude measure is Richter Scale, named for the renowned seismologist, Charles Richter. Richter Magnitude • Measure amplitude of largest S wave on seismograph record. • Take into account distance between seismograph & epicenter. Intensity • Intensity refers to the amount of damage done in an earthquake
- 95. How are theSize and Strength of an Earthquake Measured? • Modified Mercalli Intensity Map – 1994 Northridge, CA earthquake, magnitude 6.7 • Intensity – subjective measure of the kind of damage done and people’s reactions to it
- 96. How are EarthquakesMeasured? Richter Scale
- 97. 9.5 Chile, May22, 1960 9.2 Indian Ocean (Sumatra tsunami) Dec 26,2004 9.2 Prince William Sound, Alaska, March 28, 1964 9.1 Andreanof Islands, Aleutian Islands, Pacific, March 9, 1957 9.0 Kamchatka, Russia, November 4, 1952 8.8 Off the Coast of Ecuador, January 31, 1906 8.7 Rat Islands, Aleutian Islands, Pacific, February 4, 1965 8.6 India-China Border, August 15, 1950 8.5 Kamchatka, Russia, February 3, 1923 8.5 Banda Sea, Indonesia, February 1, 1938 8.5 Kuril Islands, Pacific, October 13, 1963
- 98. Earthquake Waves (Review) • PrimaryWave (P-Wave) First set of waves – Move side to side – FASTEST wave • Secondary Wave (S-Wave) Second set of waves – Move up and down – Travel slow • Surface Wave – Move up and down & side to side – MOST DANGEROUS – SLOWEST Wave
- 99. Closure • Create aVenn Diagram contrasting and comparing the 2 types of seismic waves.
- 100. Homework • Study forQuiz • Place the following words in your glossary. • Primary wave, Secondary wave, Surfaces wave, Longitudinal wave, Transverse wave, Richter Scale, Seismograph, Seismogram, Magnitude, and Intensity.
- 101. FALCON FOCUS • SWAVES CANNOT TRAVEL THROUGH LIQUIDS AND P WAVES SLOW DOWN IN LESS RIGID MATERIALS. IN EARTH’S OUTER CORE, S WAVES CANNOT BE DETECTED AND P WAVES SLOW DOWN. THESE SUGGEST THAT ____. A. THE OUTER CORE MAY BE LIQUID B. THE OUTER CORE MAY BE SOLID C. THERE ARE NO EARTHQUAKES IN THE OUTER CORE D. THE OUTER CORE IS THE THICKEST LAYER OF THE EARTH
- 102. ESSENTIAL QUESTION • INYOUR OWN WORDS, EXPLAIN HOW SEISMIC WAVES MOVE FROM THE FOCUS OF AN EARTHQUAKE?