Primary, secondary, surface (or) P, S, surface.Based on the highest amplitude wave measured on a seismogram, corrected for distance from the seismograph to the epicenter.Based on people’s reported perceptions of shaking (subjective), and the type and extent of damage produced (objective).fault offsetlength of fault rupturedacceleration of the groundtime of shakingvelocity of motion of the groundLiquefaction 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.Bricks, concrete blocks, stone, or adobe (mud).Diagonal braces or plywood sheeting built into the walls to keep the building from deforming during base shear.Broken water mains, impassable roads.Ground deformationForeshocksWater Level in WellsEmission of Radon GasAbnormal Animal BehaviorName: _______________________Learning Unit 4: Earthquake Review QuestionsThis assignment is designed to assess your understanding of Unit 4 and includes some of the Questions forReview 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 caused by the rupture and sudden movement of rocks that have been strained (deformed) beyond their elastic limit. The forces thatcause deformation and the build-up of strain energy in the rock are referred to as stresses.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, generally referenced by geographic location. 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 Fault: Convergent Boundary.5. What is the motion of a P-waves? an S-wave? Surface waves?P-waves compress and extend the rock in the direction of wave travel. S-waves shearthe rock perpendicular to the direction of wave travel. Love waves create a complex horizontal motion. Rayleigh waves create an elliptical 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 (or) P, S, surface.8. How do seismologists determine how far away an earthquake was from their seismograph?The lag time between the arrival of the first recorded P-wave and first recorded S-wave is proportional to distance traveled. Therefore they determine the lag time between the P- and S-wave arrival and, knowing the different velocities of those waves, calculate the distance.9. How do seismologists determine the location of an earthquake epicenter?They determine the distance of the earthquake from at least 3 seismographs of quite different locations and draw circles of distance from each seismograph.The earthquake is at the intersection of the 3 distance circles.10. What does the Richter Magnitude Scale depend on?Based 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?A magnitude 6 earthquake releases approximately 30 times more energy than a magnitude 5 (32X more energy to be more precise).A magnitude 7 earthquake releases approximately 900 times more energy (calculated30x30) than a magnitude 5 (32x32 = 1024 times more energy to be precise).12. What are the three main factors that affect moment magnitude?The rock strength, area of rock broken, and amount of 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 length of fault rupturedacceleration of the groundtime of shakingvelocity of motion of the ground15. Why are structures built on soft sand or mud often destroyed in an earthquake when nearby structures built on bedrock remain essentially undamaged?Bedrock is resistant to shaking and therefore shakes with small amplitude vibrations. Soft sediment amplifies shaking and therefore shakes with stronger (large amplitude) vibrations, meaning greater back and forth distances which causes more damage.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?Bricks, concrete blocks, stone, or adobe (mud).18. What type of wall strengthening is commonly used to prevent a building from being pushed over laterally during an earthquake?Diagonal braces or plywood sheeting built into the walls to keep the building from deforming during base shear.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?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 without lateral support so it bends
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