Montclair EAES 104 - Earthquake Review Questions 2

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Name: Lauren AttardiLearning Unit 4: Earthquake Review QuestionsThis 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 ques-tions. Each question can be answered in one to two sentences. Please limit yourself to a maxi-mum 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 build up and release of stress during an earthquake, it is an explanation for how energy is spread during earthquakes2. What is the difference between the epicenter and the focus of an earthquake?-The point on the Earth's surface directly above the focus is the epicenter, the focus is the place inside Earth's crust where an earthquake originates. 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?-An extensional fault is a fault caused by stretching/ extension of the Earth's crust. This would be produced at a 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?-Compression of the crust generally creates a reverse fault. This would typically be produced at a convergent plate boundary. 5. What is the motion of a P-waves? an S-wave? Surface waves?-P waves can travel through solids, liquids, and even gases. S waves shake the ground in a shearing, or crosswise, motion that is perpendicular to the direction of travel. In a surface wave, particles of the medium move up and down as well as back and forth in an overall circular motion.6. Which type of earthquake waves do the most damage?-S waves are more dangerous than P waves because they have greater amplitude and produce vertical and horizontal motion of the ground surface.7. In what order do seismic waves arrive to distant locations?-P waves travel the fastest, so they arrive first. S waves, which travel at about half the speed ofP waves, arrive later.8. How do seismologists determine how far away an earthquake was from their seismograph?-Seismologists use the difference in arrival time between P and S waves to calculate the dis-tance between the earthquake source and the seismograph. 9. How do seismologists determine the location of an earthquake epicenter?-Scientists use triangulation to find the epicenter of an earthquake. 10.What does the Richter Magnitude Scale depend on?-The Richter scale calculates an earthquake's magnitude (size) from the amplitude of the earthquake's largest seismic wave recorded by 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 6.0 earthquake releases 32 times more energy than a magnitude 5.0, and a 7.0 releases about 1,000 times more energy.12.What are the three main factors that affect moment magnitude?-The fault throw (distance the fault moved), the area broken on the fault (depth and length), and the rigidity of the fault rocks (the springiness of the rocks) determine the moment magnitude.13.What does the Mercalli Intensity Scale depend on?-The Mercalli Scale is based on observable earthquake damage.14.In addition to the amount of damage, increases in what factors go along with an increase inearthquake magnitude?-These factors include the focal depth, the distance from the epicenter, and the design of buildings and other structures.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 soft structure of sand or mud is easily destroyed by the waves and vibrations while the solid structures built on bedrock can withstand the pressure and waves.16.What is liquefaction?Liquefaction is what takes place when loosely packed, water-logged sediments at or near the ground surface lose their strength in response to strong ground shaking.17.What kinds of structural materials make dangerously weak walls during an earthquake?-Bricks, concrete blocks, stone, or adobe (mud).18.What type of wall strengthening is commonly used to prevent a building from being pushedover laterally during an earthquake?-Diagonal beams are commonly put in place to prevent damage.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 dam-age?-Use base isolation pads between the building and its foundation. The base isolation pads act as shock absorbers to minimize transfer of ground shaking to the building. 20.Freeway overpasses often collapse in a strong earthquake, even though their supports are concrete and heavy duty steel reinforcing bars. Why?-Shaking in the earthquake cracks and crumbles the concrete. that leaves the rebar withoutlateral support so it bends and the freeway collapses.21.Why are building fires so hard to fight after an earthquake?-Earthquakes shake the Earth from the core, and that can cause gas and electrical devices un-derground to be triggered. It is a major issue and hard to fight because it can happen at random and be coming from deep beneath the surface. 22.List several of the precursors that have been used to indicate that an earthquake may be coming.-radon in soil, water level, atmospheric temperature variations, VHF signals, thermal long-wave radiation, GPS/TEC and animal behavior23.There has been at least one highly successful prediction of a major earthquake that saved avery large number of lives. Where and when was that earthquake? What information lead to the prediction?-Haicheng, China, in 1975. Numerous foreshocks and very strange animal behavior helped to predict the event.24.What is a seismic gap, and what is its significance?-A seismic gap is a segment of an active fault known to produce significant earthquakes. It is significant because this is known as a seismic gap because they have not slipped in an unusu-ally long time when compared with other segments along the same structure.25.Some major faults show migration with time (e.g. over the past few hundred or a thousand years), of


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