CHAPTER 8 READING QUIZA 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, canbe 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, butnot 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 yearsFEEDBACK: The recurrence interval is the average spacing between events. Calculating the difference in ages between each disrupted layer and averaging those values gives a recurrenceinterval of 510 years. [(820 - 260) + (1200 - 820) + (2100 - 1200) + (2300 - 2100)] / 4 = (560 + 380 + 900 + 200) / 4 = 2040/4 = 510Friction 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 anearthquake'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 far-field 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 milesFEEDBACK: The point at which the seismic trace (or seismogram) intersects the horizontal axismarks the distance from the epicenter—350 miles.Interpret the travel-time curve shown. How many minutes between the arrival of the first P-waveand the arrival of the first S-wave? 18 25 7 43FEEDBACK: 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