Week 4 - Earthquakes

22) The New Madrid earthquakes are apparently related to an old buried ________. A) transform fault B) rift zone C) subduction zone D) hazardous waste dump E) oil pipeline

B) rift zone

17) The destructive power of a tsunami is due mostly to the great height of the wave. A) True B) False

A) False

3) The 2004 Indian Ocean tsunami was generated by a magnitude 9.2 earthquake along ________ off the shore of Sumatra. A) a subduction zone B) a seafloor spreading center C) an oceanic transform fault D) a continental rift zone E) a hot-spot island chain

A) a subduction zone

Love waves and Rayleigh waves

Love: 10000 miles/hr, side to side motion Rayleigh:7800mikes/hr, up and down motion, reverse an ocean waves so particles moving back

S and P waves

P: primary wave, compression wave, solids and liquids S: secondary wave, shear wave, can only move through solids

types of dip-slip faults

normal, reverse, thrust

1) The article 'The Really Big One' is focused on the Cascadia subduction zone in the Pacific Northwest of the United States. Please describe (as if you were talking to a person who is not an Earth Scientist) the geologic context for Cascadia. What kind of fault is it and why is it there?

subduction (oceanic plate under continental plate), Juan de Fuca plate is a small plate between Pacific and North American and is slowly being consumed/taken up by the North American plate. Plates are what our Earth's surface is made up of, constantly shifting to where our continents are today

18) Tsunami have long wavelengths and very short wave heights in the open ocean. A) True B) False

A) True

23) Aftershocks of the 1811-12 New Madrid, Missouri, earthquakes are still occurring today. A) True B) False

A) True

24) Pumping fluids into Earth has been found to sometimes trigger small earthquakes (magnitudes < 5). A) True B) False

A) True

25) For magnitudes above about 6, the bigger earthquake magnitude means that more people in a larger area and for a longer time will experience the intense shaking. A) True B) False

A) True

27) The largest moment magnitudes measured to date are from earthquakes that occurred in subduction zones. A) True B) False

A) True

29) The types of rock or sediment on which a structure's foundation sits are of paramount importance with respect to whether the structure will be damaged by shaking from an earthquake. A) True B) False

A) True

30) High-frequency P and S waves will have their vibrations amplified by short buildings. A) True B) False

A) True

31) Low-frequency surface waves will be amplified in tall buildings with low frequencies of vibration. A) True B) False

A) True

32) Where the frequencies of seismic waves match the natural vibration frequencies of local geology and buildings, destruction may be great. A) True B) False

A) True

35) Earthquake-induced ground motions cause buildings to sway at certain periods. In general, the taller the structure, the ________ the period. A) longer B) shorter C) period does not depend on building height

A) longer

15) The theoretical velocity of a tsunami in the deep ocean is calculated by taking the square root of the product of ________. A) the acceleration due to gravity and the depth of the ocean B) magnitude of the earthquake and the density of the seawater C) wavelength and 1.25 D) wave height and wind speed E) depth of the thermocline and water temperature

A) the acceleration due to gravity and the depth of the ocean

11) Tsunami are typically about ________ high in the open ocean, and on average 6 to 15 m high on reaching shallow water. A) 100 m B) 1 m C) 5 m D) 20 m E) 30 m

B) 1 m

19) It is virtually impossible for small ships at sea to survive a passing tsunami. A) True B) False

B) False

28) The acceleration due to gravity is 9.8 meters per second squared (32 feet per second squared), which is referred to as 1.0 g and is used as a comparative unit of measure. Earthquake accelerations have never been measured in excess of 1.0 g. A) True B) False

B) False

13) The largest historic tsunami wave run-up ever recorded was caused by a massive rockfall into the water at ________. A) Kilauea, Hawaii B) Lituya Bay, Alaska C) Crescent City, California D) Arica, Chile E) Gibraltar

B) Lituya Bay, Alaska

39) ________ occurs when a building's period matches period of passing seismic waves. A) Interference B) Resonance C) Bracing D) Base isolation E) Liquefaction

B) Resonance

21) Which state listed below is most likely to have a magnitude 9 or larger earthquake in the next several hundred years? A) Florida B) Washington C) Texas D) Wisconsin E) South Carolina

B) Washington

37) A tall office building built on a foundation designed to slide or roll with an earthquake is an example of using ________ to reduce earthquake-induced damage. A) bracing B) base isolation C) buttressing D) resonance E) framing

B) base isolation

12) The trees that died in the Pacific Northwest after the great earthquake of 1700 were killed by ________. A) mass wasting events in the days after the earthquake B) seawater after a tsunami rushed onshore C) a cloud of methane that was released from sediments during the shaking D) seawater after the land dropped below sea level E) the liquefaction of their underlying soils

B) seawater after a tsunami rushed onshore

33) The frequency of a wave is ________. A) the amount of displacement of the medium through which the wave is passing B) the number of waves passing a given point per unit time C) the time between successive waves D) the energy of the wave

B) the number of waves passing a given point per unit time

6) Earthquake-related tsunami are created by sub sea fault movements with pronounced vertical offsets of the seafloor. Such movements occur most commonly along ________. A) oceanic transform faults B) seafloor spreading centers C) subduction zones D) continental rift zones E) hot-spot island chains

C) subduction zones

9) Tsunami wavelengths are on the order of ________ in the open ocean. A) 0.1 m B) 10 m C) 100 m D) 100 km E) 10,000 km

D) 100 km

38) Which of the following is not a way to improve a building's resistance to earthquakes? A) Brace it. B) Bolt it. C) Bracket it. D) Match its period to seismic waves at that location. E) Move most of the weight to the lower floors.

D) Match its period to seismic waves at that location.

36) The intensity of an earthquake is influenced by all but which of the following? A) Earthquake magnitude B) Distance from the hypocenter/epicenter C) Type of rock or sediment making up the ground surface D) The current air pressure E) Duration of shaking

D) The current air pressure

4) Tsunami is a Japanese word that means ________ waves. A) big B) killer C) dragon D) harbor E) island

D) harbor

5) Tsunami are created by big "splashes" made in the deep ocean by all but which of the following? A) fault movements B) volcanic eruptions C) landslides D) hurricanes E) meteor impacts

D) hurricanes

7) Tsunami typically have ________ relative to wind-blown waves. A) short periods and short wavelengths B) short periods and long wavelengths C) long periods and short wavelengths D) long periods and long wavelengths E) long periods and no measurable wavelength

D) long periods and long wavelengths

2) Most of the 245,000 deaths from the 2004 Indian Ocean tsunami occurred in ________. A) Thailand B) Sri Lanka C) India D) Bangladesh E) Indonesia

E) Indonesia

16) Which of the following statements is about tsunami in the deep ocean? A) They never "feel" the bottom. B) They only "feel" the bottom if it is less than 4,000 meters deep. C) They only "feel" the bottom if it is less than 3,000 meters deep D) They only "feel" the bottom if it is less than 5,000 meters deep. E) They are always "feeling" the bottom.

E) They are always "feeling" the bottom.

3) Explain why the largest earthquakes in the world occur along subduction plate boundaries.

Earthquake magnitude is related to size and area of the slip and subduction zones form the longest, deepest/widest faults. Transform faults usually only occur deepest at 15km whereas subduction faults often go 30km+

2) In general, there is a lot more earthquake preparedness for slip along the San Andreas in California than in the Pacific Northwest. What are the factors that have contributed to the difference

There has not been an Earthquake in Pacific NW for a long time - not ever in written history. Earthquakes are always on Californians' mind. It's hard to get people to think an earthquake is a threat when it's never happened in US history before. In addition, land is sparse in Pacific NW so a lot of buildings are old and don't even have AC.

4) Explain which factors contribute to seismic wave amplitude from earthquakes and how.

Waves change amplitude and velocity depending on what kind of rock they are travelling through. In hard rock, velocity is higher and amplitude is lower. In softer rock/soil, velocity is slower but amplitude is higher.

8) The captain of a ship tells you that he once experienced a huge tsunami while sailing in the Pacific Ocean several hundred miles from any landmass. You decide that this sounds a little far-fetched because ________. A) tsunami usually occur only in the Indian Ocean and Caribbean Sea B) tsunami are rarely felt in deep water because they have long wavelengths and low heights C) the ship could not have survived passing through a major tsunami in the open ocean D) earthquakes do not occur in deep ocean waters E) the captain did not describe any tremors or shaking associated with an earthquake

B) tsunami are rarely felt in deep water because they have long wavelengths and low heights

10) Most tsunami travel at speeds of approximately ________ km per hour in the open ocean. A) 0.01 B) 10 C) 1000 D) 0.1 E) 10,000

C) 1000

20) Which of the following states has the highest earthquake risk? A) Michigan B) Wisconsin C) Arkansas D) North Dakota E) Florida

C) Arkansas

1) The 2004 ________ Ocean tsunami killed an estimated 245,000 people in 13 countries. A) Atlantic B) Pacific C) Indian D) Southern E) Arctic

C) Indian

14) Tsunami events at a coastline ________. A) always begin with a retreat of the sea B) always begin with a rising of the sea C) can start with a drawdown or rising of the sea D) are always preceded by a large rogue wave

C) can start with a drawdown or rising of the sea

34) Usually, the biggest concern in designing buildings to withstand large earthquakes is the ________ components of movement. A) upward push from the vertical B) downward pull from the vertical C) sideways push from the horizontal

C) sideways push from the horizontal