GSU GEOL 1122K - CHAPTER 8 QUIZ (20 pages)

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CHAPTER 8 QUIZ



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CHAPTER 8 QUIZ

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Pages:
20
School:
Georgia State University
Course:
Geol 1122k - Introductory Geosciences Ii
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CHAPTER 8 READING QUIZ A tsunami is a special kind of tidal wave caused by the gravitational attraction of the Sun not the Moon can get big but never bigger than 30 feet high is dangerous near its source but dies out within about 200 miles may be just a broad gentle swelling out at sea but grows as it approaches shore FEEDBACK Tsunamis are caused by volcanic or seismic activity or by undersea landslides can be up to 30 meters high and can cross entire ocean basins Earthquake prediction is not highly reliable but geologists do know that earthquakes never happen outside of seismic belts that recurrence intervals can provide accurate short term predictions that swarms always precede major earthquakes and can help with short term prediction more earthquakes happen along plate boundaries than happen at intraplate locations FEEDBACK Earthquakes can occur outside of seismic belts though they are rare Accurate short term predictions are rare and are not based on recurrence intervals which refer to the average time between successive quakes on a fault Swarms may precede major earthquakes but not always and they are often identified after an earthquake not before The only choice that is correct is that more earthquakes happen along plate boundaries than at intraplate locations Examining sedimentary bedding in a geologic study reveals disrupted layers formed 260 820 1 200 2 100 and 2 300 years ago What is the recurrence interval of the earthquakes that caused the disruption 200 years 380 years 510 years 560 years FEEDBACK The recurrence interval is the average spacing between events Calculating the difference in ages between each disrupted layer and averaging those values gives a recurrence interval of 510 years 820 260 1200 820 2100 1200 2300 2100 4 560 380 900 200 4 2040 4 510 Friction is slow but steady movement along a fault is the force that resists sliding along a surface is the process by which faults release energy happens when rock is weak and can slip smoothly without creating shock waves FEEDBACK Friction caused by bumps and snags along rock surfaces is the force that resists sliding Identify the FALSE statement Normal faults result from stretching the Earth s crust thrust faults from squeezing and shortening it Any given earthquake can have more than one magnitude but can have only one intensity Moment magnitude MW rating is considered the most accurate representation of an earthquake s magnitude All earthquake magnitude scales are logarithmic which means a difference of one unit in magnitude reading represents a 10 fold difference in ground motion FEEDBACK The magnitude of an earthquake refers to the amount of energy released Therefore a given earthquake should only have one magnitude number Identify the FALSE statement Seismic waves become smaller in amplitude with increasing distance from the epicenter Earthquake magnitude is based on ground motion recorded by a seismograph intensity is based on the amount of damage produced Contour lines representing Mercalli values are used to delimit zones of quake intensity the greater the quake the higher the intensity values and the wider the zones Earthquakes never have hypocenters foci deeper than about 100 km 60 miles FEEDBACK Hypocenters can be as deep as 660 km about 400 miles Identify the FALSE statement Long term earthquake predictions are unreliable and do not provide useful information are based on the identification of seismic zones are based on the study of historic recurrence intervals involve looking for sand volcanoes and disrupted bedding in the area FEEDBACK Long term predictions range from a few decades to centuries Identify the FALSE statement Seismometers may be the mechanical type consisting of a weight spring frame pen and revolving cylinder may be electronic consisting of a heavy cylindrical magnet and a coil of wire which produces a signal that can be recorded digitally are only sensitive enough to record ground movements down to about 1 mm operate because of inertia one part of the instrument remains motionless while the recording device moves in response to seismic waves FEEDBACK A seismograph can detect ground motion down to a mere millionth of a millimeter Identify the FALSE statement The Richter scale measures the size of a quake in terms of the damage it does its intensity measures the amplitude of the largest deflection on a seismogram in response to specifically defined seismic waves at a specifically defined distance and depth is today termed a local magnitude reading ML works well only for shallow nearby earthquakes FEEDBACK The Richter scale measures quake size in terms of the ground motion it generates its magnitude The Modified Mercalli Intensity MMI scale measures the size of an earthquake in terms of the damage it does its intensity Identify the FALSE statement The tsunami event of December 26 2004 in Indonesia involved a monstrous magnitude 9 3 earthquake that lasted 9 minutes was first noticed as a withdrawal of the sea along the beach front consisted of near field tsunamis that affected the island of Sumatra and later farfield tsunamis that struck all along the Indian Ocean coast crippled a nuclear power plant and released radioactivity into the surrounding environment FEEDBACK The earthquake and resulting tsunami that devastated a nuclear power plant occurred in 2011 in Japan not in Indonesia in 2004 Interpret the travel time curve shown How far away is the earthquake epicenter 200 miles 900 miles 350 miles 100 miles FEEDBACK The point at which the seismic trace or seismogram intersects the horizontal axis marks the distance from the epicenter 350 miles Interpret the travel time curve shown How many minutes between the arrival of the first P wave and the arrival of the first S wave 18 25 7 43 FEEDBACK Reading the vertical axis there are 7 minutes between the arrival time of the first P wave and first S wave Interpret the travel time curve shown What time did the earthquake occur 4 18 p m 4 25 p m 4 27 p m 4 16 p m FEEDBACK The P wave has been traveling for 2 minutes and it arrived at 4 18 p m it s been traveling since it came into existence at the start of the quake so 4 18 2 min 4 16 Alternatively the S wave has been traveling for 9 minutes and arrival time is 4 25 9 min 4 16 On the diagram shown block X is the footwall block X is the hanging wall the displacement of layer B shows this is a thrust fault the displacement of layer B shows this is a strike slip fault FEEDBACK This is a normal


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