Name Angel Barkley 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 The Elastic Rebound Theory describes the build up and release of stress during an earthquake 2 What is the difference between the epicenter and the focus of an earthquake Epicenter is the geographic point on Earth s surface directly above a earthquakes focus while the focus is the point is where the fault slipping begins 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 The fault that cause the extension of earth s extension is a normal fault The plate boundary produced by the extension of earth s crust is convergent 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 The fault that causes the compression of the earth s crust is the reverse fault The convergent plate boundaries are what cause reverse faults 5 What is the motion of a P waves an S wave Surface waves The motion of a P waves is in the same direction An S wave goes up and down and in a right angle and surface waves go up and down and side to side 6 Which type of earthquake waves do the most damage Seismic waves and surface waves cause the most damage in earthquakes 7 In what order do seismic waves arrive to distant locations Seismic waves arrive in distant locations in p waves s waves and surface waves 8 How do seismologists determine how far away an earthquake was from their seismograph Seismologists determine how far an earthquake is by measuring the arrival times of P waves and S waves Then using the S P time function you can figure out how far an earthquake is 9 How do seismologists determine the location of an earthquake epicenter Seismologists use triangulation using multiple seismometers to determine the earthquake epicenter 10 What does the Richter Magnitude Scale depend on The Richter Magnitude Scale depends on the maximum amplitude of earthquakes waves on 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 magnitude 6 earthquake shakes 10 times more than a magnitude 5 earthquake A magnitude 7 earthquake is 20 times more powerful than a magnitude 5 earthquake 12 What are the three main factors that affect moment magnitude The three main factors that affect moment magnitude are average slip distance of the fault shear strength of the rocks displaced and total surface area of rocks ruptured 13 What does the Mercalli Intensity Scale depend on The Mercalli Intensity Scale depend on how much damage occurred in an area 14 In addition to the amount of damage increases in what factors go along with an increase in earthquake magnitude Another factor to be considered in the Mercalli Intensity Scale is the subjective observation of people who felt the earthquake 15 Why are structures built on soft sand or mud often destroyed in an earthquake when nearby structures built on bedrock remain essentially undamaged This is due to liquefaction which liquifies soft sediment when shaken and then solidifies again after 16 What is liquefaction Liquefication is when soil liquefies when shaken then solidifies when the shaking stops 17 What kinds of structural materials make dangerously weak walls during an earthquake Structural materials that make weak walls during an earthquake are bricks stone and concrete blocks 18 What type of wall strengthening is commonly used to prevent a building from being pushed over laterally during an earthquake The types of wall strengthening used are sheets of plywood well anchored to walls and diagonal cross braces in the wall 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 Using base isolation pads between the building and foundations to absorb the shock and minimize transfer of the shock 20 Freeway overpasses often collapse in a strong earthquake even though their supports are concrete and heavy duty steel reinforcing bars Why During an earthquake the concrete cracks and crumbles so the rebar is without lateral support so it bends 21 Why are building fires so hard to fight after an earthquake Building fires are 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 Changes in seismic velocity foreshocks ground uplift tilt animal behavior radon levels and seismicity 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 In 1976 in Haicheng China a successful prediction of a major earthquake occurred that saved many lives The prediction started from months of studies of seismic activites and foreshocks that happened the day before 24 What is a seismic gap and what is its significance A seismic gap is a segment of an active fault that could potentially start an earth It is significant because it s a fault that hasn t slipped in a long time and could at any moment 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 An example of a major fault that shows migration over time is the North Anatolian Fault in Turkey