Name Learning Unit 4 Earthquake Review Questions This assignment is designed to assess your understanding of Unit 4 and includes some of the Questions for Review 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 the sudden 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 damage 7 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 Swave 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 epicenter 11 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 of rock broken and amount of offset across the fault 13 What does the Mercalli Intensity Scale depend on The Mercalli Intensity Scale depends on people s reported perceptions of shaking and the 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 earthquake 18 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 connections between different parts of a building These allow the separate areas of the building to shake independently 20 Freeway overpasses often collapse in a strong earthquake even though their supports are concrete and heavy duty steel reinforcing bars Why 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 flexible 21 Why are building fires so hard to fight after an earthquake Impassible roads and ruptured water mains compound the problem In some urban quakes fires have caused more damage than the ground shaking itself 22 List several of the precursors that have been used to indicate that an earthquake may be coming Ground deformation foreshocks water level in wells emission of radon gas abnormal animal behavior 23 There has been at least one highly successful prediction of a
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