Chapter 9 Reading Quiz

9.4 Why is the moment magnitude scale favored over the Richter scale for large earthquakes?

- it can be calculated from geologic fieldwork by measuring the average amount of slip on the fault, the area of the fault surface that slipped, and the strength of the faulted rock - this method is most effective for determining the magnitude of large earthquakes generated along large faults in which the ruptures reach the surface

9.4 What information is used to establish the lower numbers on the Mercalli scale?

- provides a tool to compare earthquake severity - (I-V) refer to what people in various locations flt during the earthquake

*9.7 Compare and contrast the goals of short-range earthquake predictions and long-range forecasts.

-Short range earthquake predict

9.6 List two reasons a repeat of 1811-1812 New Madrid, Missouri, earthquakes could be destructive in the Memphis, Tennessee metropolitan area.

1) Memphis is located on unconsolidated floodplain deposits and the buildings are more susceptible to damage. 2) Materials used for foundations are weak and building design criteria is very bad

9.4 How much more energy does a magnitude 7.0 earthquake release than a magnitude 6.0 earthquake?

10 times

9.1 How are faults, hypocenters (focus), and epicenters related?

A fault is a large fracture along which there is movement. When movement occurs, the zone within Earth where rock displacement occurs is termed the hypocenter (focus). The point on Earth's surface directly above the focus of an earthquake is called the epicenter.

9.5 What is a tsunami? How are tsunamis generated?

A tsunami is a large undersea earthquake occasionally causing massive waves Most tsunami are caused by the vertical displacement of a slab of seafloor along a fault on the ocean floor, or less often by a large submarine landslide triggered by an earthquake

9.1 What is the approximate duration of an earthquake that occurs along a 300-kilometer - (200 mile -) long fault?

About 1.5 minutes

9.6 Name another major concentration of strong earthquake activity.

Alpine-Himalayan Belt

9.1 What is an earthquake? Under what circumstances do most large earthquakes occur?

An earthquake is the vibration of Earth produced by the rapid release of energy, usually along a fault. A fault is a large fracture along which there is or has been movement. When slippage occurs, an earthquake results.

*9.5 List and describe the major destructive forces that earthquake vibrations can trigger.

Buildings constructed out of unreinforced masonry (bricks and blocks) are more likely than any other types of buildings to collapse in a quake. Buildings not built on bed-rock tend to collapse because loose sediment amplifies seismic shaking. If a building is on water-logged sediments or soil, liquefaction can occur. The ground material, when shaken at certain frequencies, will flow like a liquid. Buildings may sink into the ground and underground tanks or sewer lines may float up to the surface. Landslides or ground subsidence (the raising or lowering of the ground surface) can result in destruction or death. The earthquake may break gas lines which can initiate devastating fires. Tsunamis can be generated. The are large destructive ocean waves that form when water is displaced.

9.6 What is the zone of the greatest amount of seismic activity?

Circum-Pacific Belt

9.9 How do continental crust and oceanic crust differ?

Continental crust is less dense, thicker, and made up of mostly granitic rocks Oceanic crust is thinner, denser, and made up of mostly basaltic rock.

9.6 What type of plate boundary is associated with Earth's largest earthquakes?

Convergent plate boundaries

*9.9 List and describe each of Earth's major layers.

Crust - top strong rocky layer Mantle - beneath the crust; solid, rocky shell. Core - middle of Earth, made of iron-nickle alloy. Very hot

9.8 How did Earth acquire its layered structure?

Differentiation of the material when our planet was entirely molten. The less dense material "floats" toward the surface and the denser material "sinks" towards the core.

9.1 Defend or rebut this statement: Faults that do not experience fault creep may be considered safe.

False- because faults that produce "creeps" produce little seismic shaking, therefore are safe

9.5 In addition to the destruction created directly by seismic vibrations, list three other types of destruction associated with earthquakes.

Fire Landslides and ground subsidence Seismic sea waves (tsunamis) are all capable of adding to the destructive nature of earthquakes.

9.5 List at least three reasons an earthquake with a magnitude of 7.0 might results in more death and destruction than a quake with a magnitude of 8.0.

Fire - fire can break out with a magnitude of 7.0 Earthquake can create a firestorm which fans out due to wind Tsunami - earthquake that is triggered at a mega thrust fault will create a tsunami which leads to larger damage Landslide - ground is converted and it slumps away. Major destruction follows.

9.1 Who was the first person to explain the mechanism by which most earthquakes are generated?

H. F. Reid

9.3 What information does a travel-time graph provide?

Helps to determine the distance separating the recording station form the earthquake's epicenter

9.5 List four factors that affect the amount of destruction that seismic vibrations cause to human-made structures.

Intensity Duration of vibrations Nature of the material on which structures rest The nature of building materials and construction practices of the region

*9.4 Distinguish between intensity scales and magnitude scales.

Intensity scales measure the amount of ground shaking a place experiences due to an earthquake. Magnitude scales are an estimate of the actual amount of energy released during an earthquake. *Credit to Liberty.org

9.4 What does the Modified Mercali Intensity scale tell us about an earthquake?

It helps to designate a label to a certain intensity of an earthquake

9.7 What is the value of long-range earthquake forecasts?

Long-range predictions are statistical estimates of how likely it is for an earthquake of a given magnitude to occur. They are useful because they can be used to guide building codes and infrastructure development so that buildings, dams, and roadways are constructed to withstand expected levels of ground shaking. *Credit to Liberty.org

*9.6 Locate Earth's major earthquake belts on a world map and label the regions associated with the largest earthquakes.

Look at map on 256

9.1 What type of faults tend to produce the most destructive earthquakes?

Mega thrust faults

9.7 Are accurate, short-range earthquake predictions currently possible using modern seismic instruments? Explain.

No, there is no technique that is consistently accurate in predicting the location and timing of earthquakes

9.2 List the major differences between P, S, and surface waves.

P waves travel through all materials, whereas S waves are propagated only through solids. Further, in all types of rock, P waves travel faster than S waves.

*9.8 Explain how Earth acquired its layered structure and briefly describe how seismic waves are used to probe Earth's interior.

Seismic waves are reflected, refracted, and diffracted as they pass through the planet. They reflect off boundaries between different layers, they refract when passing from one layer to another layer, and they diffract around any obstacles they encounter. This gives us a "picture" of what the interior is made of.

9.8 Briefly describe how seismic waves are used to "see inside" Earth's interior.

Seismic waves are reflected, refracted, and diffracted as they pass through the planet. They reflect off boundaries between different layers, they refract when passing from one layer to another layer, and they diffract around any obstacles they encounter. This gives us a "picture" of what the interior is made of.

9.2 Which type of seismic waves tend to cause the greatest destruction to buildings?

Surface waves

*9.2 Compare and contrast the type of seismic waves and describe the principle of the seismograph

Surface waves - travel through rock layers, just below Earth's surface Body waves - travel through Earth's interior The inertia of the suspended weight tends to keep it motionless while the recording drum, which is anchored to the bedrock, vibrates in response to seismic waves. The stationary weight provides a reference point from which to measure the amount of displacement occurring as a seismic wave passes through the ground.

9.9 Contrast the physical makeup of the asthenosphere and the lithosphere.

The asthenosphere has the ability to flow over long periods of time and the lithosphere is rigid and behaves in a brittle manner.

9.2 Describe the principle of the seismograph.

The inertia of the suspended weight tends to keep it motionless while the recording drum, which is anchored to the bedrock, vibrates in response to seismic waves. The stationary weight provides a reference point from which to measure the amount of displacement occurring as a seismic wave passes through the ground.

9.9 How are Earth's inner and outer cores different? How are they similar?

The outer core is a liquid layer and the inner core is solid

9.6 Explain why an earthquake east of the Rockies may produce damage over a larger area than one of similar magnitude in California.

The reason is that the underlying bedrock in the central and eastern United States is older and more rigid. As a result, seismic waves are able to travel greater distances with less attenuation than in the western United States.

9.3 Briefly describe the triangulation method used to determine the epicenter of an earthquake.

This method involves using the distance obtained from three or more seismic stations to establish the location of an earthquake

*9.1 Sketch and describe the mechanism that generates most earthquakes

Those four pictures and steps on the left side of page 242

*9.3 Explain how seismographs are used to locate the epicenter of an earthquake.

Through triangulation. This method involves using the distance obtained from three or more seismic stations to establish the location of an earthquake

9.1 Explain what is meant by elastic rebound.

slippage allows the deformed rock to "snap back" to its original, stress free shape; "springing back"; similar to a rubber band