MULTIPLE CHOICE
 

1. Earthquakes occur most often in the __________ region of the United States.

a. Northeast
b. Mississippi Valley
c. Pacific coastal
d. West
e. Southwest
 

2. What instrument is used to measure the magnitude of an earthquake?

a. seismometer
b. seismogram
c. seismograph
d. richtermeter
e. richtergraph
 

3. Earthquake epicenters are pinpointed by at least three stations and then calculating

a. radial distance
b. centrifugal distance
c. axial distance
d. arc
e. perimiter of the circle
 

4. How can the type of earthquake be determined from seismographs?

a. time of first P-wave arrival
b. time of first S-wave arrival
c. from the frequency of the wave
d. location of the epicenter
e. from the amplitude of the wave

feedback
the shape of the amplitude disturbance also indicates the type of earthquake.

5. A scale for measuring eqrthquakes is called

a. seismometer
b. Modified Mercalli
c. Richter magnitude
d. b and c
e. a, b, and c

feedback
Richter Magnitude is the scale most people are familiar with, but scientists use other more accurate scales. Another nonscientific way of measuring earthquakes is by their intensity or degree of shaking. Intensity is descriptive, and is determined by inspection of damage and other effects, with the greatest intensity being close to the epicenter, and smaller intensities further away.  The Modified Mercalli Intensity Scale uses Roman Numerals from I to XII to describe different earthquake effects is commonly used.
 

6. After an earthquake, a formerly straight line that crosses a fault line will be distorted into a shape having _________  displacement near the fault through a process called  ___________.

a. Increasing, isostatic rebound
b. Increasing, elastic rebound
c. Decreasing, isostatic rebound
d. Decreasing, elastic rebound
e. Decreasing, static and dynamic forces
 
feedback
typically, someone will build a straight reference line such as a road, railroad, pole line, or fence line across the fault while it is in the pre-rupture stressed state. After the earthquake, the formerly straight line is distorted into a shape having increasing displacement near the fault, a process known as elastic rebound.
 

7. Compressional waves are  __________  and   ______________.

a. are P waves, travel slow
b. are S waves, travel fast
c. are P waves, travel fast
d. are S waves, travel slow
e. are the same as shear waves, travel the fastest

feedback
the mechanical properties of the rocks that seismic waves travel through quickly organize the waves into two types. Compressional waves, also known as primary or P waves, travel fastest, at speeds between 1.5 and 8 kilometers per second in the Earth's crust.   Shear waves, also known as secondary or S waves, travel more  slowly, usually at 60% to 70% of the speed of P waves.
 

8. P-waves shake the ground  ____________ to the direction of propogation, while S-waves travel  _______ to the direction of propogation.

a. perpendicular, transverse
b. perpendicular, parallel
c. transverse, parallel
d. transverse, perpendicular
e. parallel, perpendicular

feedback
P waves shake the ground in the direction they are propagating,  while S waves shake perpendicularly or transverse to the  direction of propagation.
 

9. What types of earthquakes create the biggest tsunamis?

a. static
b. dynamic
c. transverse
d. concave
e. subduction

feedback
Large vertical movements of the earth's crust can occur at plate boundaries. Plates interact along these boundaries called faults.  Around the margins of the Pacific Ocean, for example, denser oceanic plates slip under continental plates in a process known as subduction. Subduction earthquakes are particularly effective in generating tsunamis.
 

10. Tsunamis travel at a speed that is related to water depth.  Which of the following choices are true?

a. as water depth decreases, tsunamis speed up
b. as water depth decreases, tsunamis slow down
c. as water depth increases, tsunamis speed up
d. as water depth increases, tsunamis slow down
e. both depend on the topography of the ocean bottom

feedback
tsunami travels at a speed that is related to the water depth - hence, as the water depth decreases, the tsunami slows
 

11. The height of a tsunami may reach up to

a. 100 feet
b. 30 feet
c. 30 meters
d. 20 meters
e. 5 meters

feedback
Tsunamis may reach a maximum vertical height onshore above sea level, often called a runup height, of 10, 20, and even 30 meters
 

12. How fast does seismic energy travel?

a. 3-6 miles/hour
b. as fast as sound
c. 1-2 km/sec
d. 3-6 km/sec
e. 7-9 km/sec

feedback
The sensors closest to the epicenter of a particular earthquake would transmit data at the speed of light to a central processing center, which would broadcast an area-wide alarm in advance of the spreading elastic wave energy from the earthquake. This is possible because seismic energy travels slowly (3 to 6 km/s) compared to the speed of light.
 

13. Earthquakes of magnitude < 2.0 occur by a factor of ___ more frequently than those of 4.0-4.9

a. 1
b. 2
c. 3
d. 4
e. 5

feedback
c. 3 -  magnitude 4.0-4.0 occur  6,000 times per year, while magnitude less than 2.0 occur 600,000+ times per year
 

14. Earthquakes can occur in the earth’s _________ at maximum depths to approximately  _________.

a. crust, 500 feet
b. upper mantle, 500 miles
c. crust, 800 km
d. b and c
e. a and c

feedback
Earthquakes occur in the crust or upper mantle which ranges from the surface to about 800 kilometers deep (about 500 miles)
 

15. What percentage of earthquakes occur in intra-plate zones?

a. 15%
b. 80%
c. 95%
d. 1%
e. 5%

feedback
On active plate boundaries about 95% of all the world's earthquakes occur.  Only 5% are in
areas of the plates far away from the boundaries. These are called mid-plate or intra-plate earthquakes and are, as yet, poorly understood.
 

16. What are some ways earthquakes can be accurately predicted?

a. Richter scale
b. Doppler radar
c. Seismographs
d. Assigning a series of probabilities and range of years and magnitude to a region
e. Earthquakes cannot be accurately predicted

feedback
An earthquake prediction involves assigning a specific date, location, and magnitude for an earthquake. A forecast assigns a series of probabilities and a range of years and magnitudes to a region. There is no way to accurately predict earthquakes, but forecasts have been calculated for different areas of the United States. The earthquake in northern California on October 17, 1989 was not predicted, but did fall within the magnitude range, time span, and region forecast by U.S. Geological Survey staff.
 

17. Earthquakes are related to volcanoes in the following ways:

a. Volcanic eruptions cause earthquakes
b. The same processes are responsible for volcanoes and earthquakes
c. Earthquakes are the result of active forces connected with a volcanic eruption
d. Earthquakes cause volcanoes to erupt
e. Earthquakes and volcanoes always occur together

feedback
Different earth processes responsible for volcanoes and earthquakes. Earthquakes may occur in an area before, during, and after a volcanic eruption, but they are the result of the active forces connected with the eruption, and not the cause of volcanic activity
 

18. Static deformation is:

a. permanent displacement of the ground
b. semi-permanent displacement of the ground
c. a dynamic process
d. dissipates immediately
e. a permanent displacement of an area 50 m surrounding a fault

feedback
When an earthquake fault ruptures, it causes two types of deformation: static; and dynamic. Static deformation is the permanent displacement of the ground due to the event. The earthquake cycle progresses from a fault that is not under stress, to a stressed fault as the plate tectonic motions driving the fault slowly proceed, to rupture during an earthquake and a newly-relaxed but deformed state.
 

19. Dynamic motions

a. are caused by shear waves
b. account for 10% of the energy from a fault
c. are sound waves radiated from the earthquake epicenter
d. b and c
e. a, b, and c

feedback
The second type of deformation, dynamic motions, are essentially sound waves radiated from the earthquake as it ruptures. While most of the plate-tectonic energy driving fault ruptures is taken up by static deformation, up to 10% may dissipate immediately in the form of seismic waves
 

20. Another use of a seismograph is:

a. monitoring volcanoes
b. monitoring tsunamis
c. monitoring hurricanes
d. monitoring nuclear tests
e. none of the above

feedback
The dynamic, transient seismic waves from any substantial earthquake will propagate all around and entirely through the Earth.  Given a sensitive enough detector, it is possible to record the seismic waves from even minor events occurring anywhere in the world at any other location on the globe. Nuclear test-ban treaties in effect today rely on our ability to detect an uclear explosion anywhere equivalent to an earthquake as small as Richter Magnitude 3.5.
 

21. The 4 major types of earthquakes detected by seismographs are:

a. tectonic, deep, superficial, harmonic
b. tectonic, shallow, substrate, transverse
c. subduction, shallow, surface, dynamic
d. static, dynamic, transverse, concave
e. tectonic, shallow, surface, harmonic

TRUE/FALSE

1. San Diego California is the location of the feasibility study for earthquake alerts
 
 False   This is a feasibility study being done for the San Francisco, California area
 
 
2. A tsunami is another word for tidal wave
 
 False.  Tsunami is a Japanese word with the English translation, "harbor wave." Represented by two characters, the top character, "tsu," means harbor, while the bottom character, "nami," means "wave." In the past, tsunamis were sometimes referred to as "tidal waves" by the general public, and as "seismic sea waves" by the scientific community. The term "tidal wave" is a misnomer; although a tsunami's impact upon a coastline is dependent upon the tidal level at the time a tsunami strikes, tsunamis are unrelated to the tides. Tides result from the imbalanced, extraterrestrial, gravitational influences of the moon, sun, and planets. The term "seismic sea wave" is also misleading. "Seismic" implies an earthquake-related generation mechanism, but a tsunami can also be caused by a nonseismic event, such as a landslide or meteorite impact.
 
 
3. The largest earthquake in the United States occurred in Alaska
 
 True.  Alaska has more earthquakes per year than the combined total of the rest of the United States. As many as 4,000 are recorded there every year. Alaska is on a plate boundary where one plate is sliding along another, a subduction zone.
 
 
4. Earthquakes are related to weather.  Particularily winds trapped in sub-terranean caves
 
 False. In the 4th Century B.C., Aristotle proposed that earthquakes were caused by winds trapped in subterranean caves. Small tremors were thought to have been caused by air pushing on the cavern roofs, and large ones by the air breaking the surface. This theory lead to a belief in earthquake weather, that because a large amount of air was trapped underground, the weather would be hot and calm before an earthquake.
 
 A later theory stated that earthquakes occurred in calm, cloudy conditions, and were usually preceded by strong winds, fireballs, and meteors.  There is no connection between weather and earthquakes. They are the result of geologic processes within the earth and can happen in any weather and at any time during the year.
 
 
5. Tsunami’s can be caused by earthquakes, landslides, volcanic eruptions, explosions, cosmic bodies

True. A tsunami (pronounced tsoo-nah-mee) is a wave train, or series of waves, generated in a body of water by an impulsive disturbance that vertically displaces the water column. Earthquakes, landslides, volcanic eruptions, explosions, and even the impact of cosmic bodies, such as meteorites, can generate tsunamis
 
 
 
 
 
 
 
 

Teacher

1. Explain a logarithmic scale.
 
 The Richter Scale is not an actual instrument. It is a measure of the amplitude of seismic waves and is related to the amount of energy released. This can be estimated from the recordings of an earthquake on a seismograph. The scale is logarithmic, which means that each whole number on the scale increases by 10. A magnitude 6.0 earthquake is 10 times greater than a 5.0, a 7.0 is 100 times greater, and a magnitude
 8.0 is 1,000 times greater.
 
 
2. Explain why P and S waves can be used to estimate the distance of an earthquake.
 
 Although wave speeds vary by a factor of ten or more in the Earth, the ratio between the average speeds of a P wave and of its following S wave is quite constant. This fact enables seismologists to simply time the delay between the arrival of the P wave and the arrival of the S wave to get a quick and reasonably accurate estimate of the distance of the earthquake from the observation station. Just multiply the S-minus-P (S-P) time, in seconds, by the factor 8 km/s to get the approximate distance in kilometers.
 
 
3. Explain how earthquake locations are estimated using 3 stations’ data.
 
 Given a single seismic station, the seismogram records will yield a measurement of the S-P time, and thus  the distance between the station and the event. Multiply the seconds of S-P time by 8 km/s for the kilometers of distance. Drawing a circle on a map around the station's location, with a radius equal to the
 distance, shows all possible locations for the event. With the S-P time from a second station, the circle
 around that station will narrow the possible locations down to two points. It is only with a third station's
 S-P time that you can draw a third circle that should identify which of the two previous possible points is
 the real one.
 
 
4. Describe how a tsunami is formed.
 
 A tsunami (pronounced tsoo-nah-mee) is a wave train, or series of waves, generated in a body of water by an impulsive disturbance that vertically displaces the water column. Earthquakes, landslides, volcanic eruptions, explosions, and even the impact of cosmic bodies, such as meteorites, can generate tsunamis.
 
 
5. Explain how water waves and tsunamis differ.

As a result of their long wave lengths, tsunamis behave as shallow-water waves. A wave becomes a shallow-water wave when the ratio between the water depth and its wave length gets very small. Shallow-water waves move at a speed that is equal to the square root of the product of the acceleration of gravity (9.8 m/s/s) and the water depth - let's see what this implies: In the Pacific Ocean, where the typical water
depth is about 4000 m, a tsunami travels at about 200 m/s, or over 700 km/hr. Because the rate at which a wave loses its energy is inversely related to its wave length, tsunamis not only propagate at high speeds, they can also travel great, transoceanic distances with limited energy losses.