Name Joshua Fernandez 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 How energy is spread during earthquakes 2 What is the difference between the epicenter and the focus of an earthquake The focus is the point on the fault where ruptures occur and the location from which seismic waves are released epicenter is the location directly above the focus on the earth s surface 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 Causes normal faults rift 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 Causes reverse or thrust faults ocean continent or continent continent boundaries 5 What is the motion of a P waves an S wave Surface waves P waves compress and extend in the direction of wave travel S waves travel at right angles to the direction of wave motion Surface waves travel parallel to the earth s surface 6 Which type of earthquake waves do the most damage 7 Surface waves In what order do seismic waves arrive to distant locations First would be P waves then S waves followed by surface waves 8 How do seismologists determine how far away an earthquake was from their seismograph Based on the lag time between the p waves and s waves to calculate the distance of an earthquake 9 How do seismologists determine the location of an earthquake epicenter Measuring the difference in time between the p and s waves 10 What does the Richter Magnitude Scale depend on Based on the highest amplitude wave measured on a seismogram 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 Almost 30x more energy 60x more energy 12 What are the three main factors that affect moment magnitude Rock strength area of rock broken amount of offset across the fault 13 What does the Mercalli Intensity Scale depend on How strong people felt and how much damages has happened 14 In addition to the amount of damage increases in what factors go along with an increase in earthquake magnitude Increase in time of the shaking 15 Why are structures built on soft sand or mud often destroyed in an earthquake when nearby structures built on bedrock remain essentially undamaged Bedrock shakes with smaller amplitude vibrations soft sand or mud shakes with stronger vibrations 16 What is liquefaction Quicksand like condition that happens in water saturated soil and rock earthquakes causes the soil and rock to weaken making buildings sink 17 What kinds of structural materials make dangerously weak walls during an earthquake 18 What type of wall strengthening is commonly used to prevent a building from being pushed over laterally during an earthquake Having shear walls which are diagonal braces added to walls to keep the building from Brick and stone deforming 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 Have base isolation putting the building n large rubber pads to allow the ground to move under the building 20 Freeway overpasses often collapse in a strong earthquake even though their supports are concrete and heavy duty steel reinforcing bars Why The concrete is getting cracked and weakened only leaving the steel bars resulting in bending 21 Why are building fires so hard to fight after an earthquake Because of broken water mains 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 abnormal animal behavior 23 There has been at least one highly successful prediction of a major earthquake that saved a very large number of lives Where and when was that earthquake What information lead to the prediction 1975 in northeastern China foreshock activity bulging of ground surface near fault changes in groundwater levels strange animal behavior 24 What is a seismic gap and what is its significance Is a section of an active fault that has not had a recent earthquake Since it was inactive for so long there could be energy storing up for a strong earthquake in the near future 25 Some major faults show migration with time e g over the past few hundred or a thousand years of earthquakes along the fault Name one such fault or indicate exactly where it is North Anatolian Fault in Turkey
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