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Published byHerbert Jones Modified over 4 years ago

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Coach Williams Room 310B

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Earthquakes

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Objectives: 1.Define stress and strain as they apply to rocks 2.Distinguish among the three types of faults 3.Contrast three types of seismic waves

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Vibrations of ground Caused by movement along fractured crust

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Stress: forces that act on a material ◦ Compression: decreases volume of material ◦ Tension: pulls material apart ◦ Shear: causes materials to twist Strain: deformation of material due to stress

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Fault: fracture in crust; caused by stress ◦ Reverse: horizontal compression (pushing together) ◦ Normal: horizontal pulling apart ◦ Strike-Slip: shear forces (sideways)

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Primary (P-waves): rocks move in same direction as waves. Secondary (S-waves): rocks move @ right angles to direction of wave. Surface: rocks move in 2 directions Surface waves stay on surface S/P Waves pass through interior (body waves)

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Focus: point where Earthquakes start ◦ Usually below surface Epicenter: point directly above on surface

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Objectives: 1.Describe how a siesmometer works 2.Explain how seismic waves have been used to determine the structure and composition of Earth’s interior

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Seismology: study of earthquake waves ◦ Surface and interior Seismometer: detects/records seismic waves Seismogram: record of waves

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Many earthquakes are charted Shows time an distance from epicenter Determines distance

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Changing speed/direction of waves P-waves diffracted S-waves won’t go through liquid

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Objectives: 1.Compare/contrast earthquake magnitude and intensity and the scales used to measure each 2.Explain why data from at least three seismic stations are needed to locate an earthquake’s epicenter 3.Describe Earth’s seismic belts

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Magnitude: amount of energy released Depth affects magnitude Richter scale: ◦ Measured magnitude ◦ Largest wave ◦ Power of 10 (8 is 10x larger than 7 & 100x more than 6) Moment Magnitude Scale ◦ Fracture length and movement Modified Mercalli Scale ◦ Amount of damage (intensity) ◦ I-XII

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Distance from 3 seismic stations Intersecting 3 circles

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Plotted earthquakes Regions

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Objectives: 1.Discuss factors that affect eh amount of damage done by an earthquake 2.Explain some of the factors considered in earthquake probability studies 3.Define seismic gaps

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Structure failure ◦ Buildings (pancaking), building materials? Land/Soil failure ◦ Landslides, soil liquefaction Fault scarps: ground deformations Tsunami: large ocean wave

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Earthquake history: ◦ Intervals (Parkfield, CA- 22years) ◦ Seismic gaps: time since last earthquake Strain accumulation: measure of strain

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