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 Earthquakes are vibrations of the earth by the movements of rocks that have been deformed past their limit 2 What is the difference between the epicenter and the focus of an earthquake The focus is the point where the rupture happens and the epicenter is the point right 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 Normal dip slip fault divergent boundary 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 Reverse dip slip convergent boundary 5 What is the motion of a P waves an S wave Surface waves P waves compress and extend the rock S waves shear the rock and surface waves l and r make a complex horizontal motion and create rolling motion 6 Which type of earthquake waves do the most damage Surface waves 7 In what order do seismic waves arrive to distant locations Primary secondary surface 8 How do seismologists determine how far away an earthquake was from their seismograph The lag time between the arrival of the p wave and the s wave 9 How do seismologists determine the location of an earthquake epicenter They determine the distance of the earthquake from 3 seismographs from different locations and draw circles for the distance 10 What does the Richter Magnitude Scale depend on The logarithm of height from a seismograph 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 A 6 magnitude is 32 times greater than a 5 magnitude A 7 magnitude is more than 1 000 times greater than a 5 magnitude 12 What are the three main factors that affect moment magnitude The rock strength and broken rock are offset across the fault 13 What does the Mercalli Intensity Scale depend on Based on people s reported perceptions of shaking subjective and the type and extent of damage produced objective 14 In addition to the amount of damage increases in what factors go along with an increase in earthquake magnitude Fault offset time of shaking acceleration of the ground 15 Why are structures built on soft sand or mud often destroyed in an earthquake when nearby structures built on bedrock remain essentially undamaged The bedrock shakes from small amplitude vibrations 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 Concrete and masonry structures are brittle and thus more susceptible to damage 18 What type of wall strengthening is commonly used to prevent a building from being pushed over laterally during an earthquake Diagonal Beams 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 Base isolation pads can be used between the building and the foundation 20 Freeway overpasses often collapse in a strong earthquake even though their supports are concrete and heavy duty steel reinforcing bars Why The shaking from the earthquake cracks the concrete which leaves the rebar with no support and the freeway will collapse 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 Microearthquakes changes in groundwater levels weird 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 It was in Haicheng China in 1975 There were many foreshocks and weird behavior in the animals 24 What is a seismic gap and what is its significance A seismic gap is a section of an active fault that has not had a recent earthquake It is significant because there can be a quake may occur soon 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 It is the North San Anatolian in Turkey
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