The Mercalli Intensity Scale depends on people’s reported perceptions of shaking, and the type and extent of damage produced.Liquefaction is a quicksand like condition that occurs in water-saturated soil and rock. The shaking of earthquake waves causes the soil or rock to turn into a weak, fluid-like mass. Structures built on areas that liquefy may fall over or sink.Overpasses often collapse because they do not have the right kind of construction built in. In the new construction practices to reduce failure of highway overpasses now are supposed to include horizontal rebar wrapping added when casting concrete columns and retro fitting existing columns with steel jackets to make them stronger and more flexibleImpassible roads and ruptured water mains compound the problem. In some urban quakes, fires have caused more damage than the ground shaking itself.Ground deformation, foreshocks water level in wells, emission of radon gas abnormal animal behavior.Name: _______________________Learning Unit 4: Earthquake Review QuestionsThis assignment is designed to assess your understanding of Unit 4 and includes some of the Questions forReview at the end of Chapters 3 and 4 from your text plus a few additional questions. Each question can be answered in one to two sentences. Please limit yourself to a maximum of three sentences. Access the assignment, complete it with ANSWERS IN A DIFFERENT COLOR FONT as a separate file, and send it back for evaluation and grading through the assignment tab by or before the due date. 1. What is meant by the “elastic rebound theory”?Under Elastic rebound theory, the waves of energy from an earthquake result from thesudden release of stored up strain energy in rock as it deforms. When the rock ruptures the rock on either side of a fault snaps suddenly to a new position, releasing the stored up strain energy in the process.2. What is the difference between the epicenter and the focus of an earthquake?The focus is the point on the fault where rupture occurs and the location from which seismic waves are released. The epicenter is the point on the earth’s surface directly above the focus. 3. Extension of the Earth’s crust generally causes what type of fault or faults? What type of plate boundary would produce such a fault or faults?Those kinds of faults are called strike slip faults, or reverse faults, and they occur in transform boundaries 4. Compression of the Earth’s crust generally causes what type of fault or faults? What type of plate boundary would produce such a fault or faults?Those kinds of faults are called dip slip faults, or reverse faults, and they occur in seduction boundaries 5. What is the motion of a P-waves? an S-wave? Surface waves?P-waves have the motion of push-pull waves and S-waves are in the motion of shear waves. Surface wave travel parallel to earth’s surface, involve the greatest ground motion.6. Which type of earthquake waves do the most damage?Surface waves, because the travel so close to earth’s surface, they cause so much damage7. In what order do seismic waves arrive to distant locations?First p-waves arrive, then s-waves arrive, and then surface waves arrive.8. How do seismologists determine how far away an earthquake was from their seismograph?the lag time between the arrival of your first recorded P-wave and first recorded S-wave is proportional to distance traveled.9. How do seismologists determine the location of an earthquake epicenter?By calculating the lag time between the arrival of your first recorded P-wave and first recorded S-wave is proportional to distance traveled, and if those calculations are done about three different seismic stations, then the precisely locate the epicenter can be fond. 10. What does the Richter Magnitude Scale depend on?The Richter Scale is depended on the highest amplitude wave measured on a seismogram, corrected for distance from the seismograph to the epicenter11. How much greater energy is released by a magnitude 6 earthquake than a magnitude 5 earthquake? How much greater energy is released by a magnitude 7 earthquake than a magnitude 5 earthquake?Between a magnitude 6 earthquake and a magnitude 5 earthquake, the logarithmic scale measures the energy produced from an earthquake, and each unit represents a ten-fold increase in wave, so 6 is a whole level up from 5 in terms of magnitude on the logarithmic scale. Between 7 and 5, that is two units of measure on the logarithmic scale and represents two separate increases in units of ten as the magnitude moves from 5, up to 7.12. What are the three main factors that affect moment magnitude?The three main factors that effect movement magnitude are the rock strength, area ofrock broken, and amount of offset across the fault13. What does the Mercalli Intensity Scale depend on?The Mercalli Intensity Scale depends on people’s reported perceptions of shaking, andthe type and extent of damage produced.14. In addition to the amount of damage, increases in what factors go along with an increase in earthquake magnitude?the more intense the shaking, the longer the duration of shaking, and the greater the displacement.15. Why are structures built on soft sand or mud often destroyed in an earthquake when nearby structures built on bedrock remain essentially undamaged?Shaking from the earthquake is made worse as waves travel from solid bedrock to unconsolidated sediment to water-saturated sediment.16. What is liquefaction?Liquefaction is a quicksand like condition that occurs in water-saturated soil and rock. The shaking of earthquake waves causes the soil or rock to turn into a weak, fluid-like mass. Structures built on areas that liquefy may fall over or sink.17. What kinds of structural materials make dangerously weak walls during an earthquake?Base shears, which are short walls are the weakest and cripple the easiest in an earthquake18. What type of wall strengthening is commonly used to prevent a building from being pushed over laterally during an earthquake?Base isolation is putting the building on large rubber pads, rolling wheels, or slippery Teflon plates. This allows the ground to move under the building, which then causes isolating the building somewhat from ground motion.19. What can be done to a building, either during construction or after, to reduce the shaking of the building during an earthquake and therefore reduce the possibility of severe damage?Seismic joints are areas of flexible material, like rubber, form
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