Earthquakes

Daily Web Guide

| Syllabus | Schedule | Email Kerry Magruder |

Assignments	Chernicoff, Earthquakes, ch. 10. Study pages 180-182, 186-188, Highlight 10-1 on p. 190, and 191-197.
Reminders	Check out the new information posted in the hallway exhibit.... Can you identify the "Bert" of the month?

Lesson Outline

Read the assigned portions of each chapter. Study the illustrations. Focus your attention on the vocabulary terms found in the following notes.

Historical Examples

1. Page 181 (Kobe, Japan; Manzanillo, Mexico; Loma Prieta, California)
2. New Madrid, Missouri (Highlight 10-1, p. 190)
3. Lisbon, Portugal, 1755
   1. November 1, 9:50, 10:00 a.m. and noon. First shock magnitude 9.0, greatest earthquake in recorded history.
   2. >50,000 fatalities.
   3. Occurred on All Saints' Day, during mass, or fatalities would have been higher. Devastation of a wealthy capital city.
   4. Shocks felt in Great Britian, Sweden (nearly 2,000 miles away).
   5. Tsunami, waves 50 feet high. 12-foot waves at Antiqua in the West Indies, 3,540 miles away.
   6. Rousseau (tout est bien) versus Voltaire (Le mal est sur la terre; Poem upon the Lisbon Disaster, Candide).
4. China. Deaths from automobile accidents in US per year: 50,000 (greatest hazard to life in US). This is less than a tenth of China's average earthquake toll per year since world war two.

Causes

1. Sudden release of accumulated strain energy
2. Creation of new faults by rupturing rocks
3. Shifting of rocks at pre-existing faults
4. Terms
   1. The precise subterranean location where rocks begin to rupture or shift is known as an earthquake's ___________.
      1. 90% of all earthquakes have shallow foci
      2. Most catastrophic earthquakes have foci <60 km
      3. No earthquakes deeper than 700 km
   2. An earthquake's ______________ is the point on the Earth's surface directly above the spot where rocks begin to rupture.
      1. Does it coincide with a point on the fault?
      2. How is it located?
      3. What is the value of locating it?
   3. Numerous, generally smaller, earthquakes or ______________, occur as rocks adjust to their new positions following the initial quake.
5. Sporadic recurrence of earthquakes
   1. Accumulation of energy
   2. Sudden release
   3. Rocks lock back in place
6. When an earthquake occurs, the released energy is transmitted through the Earth as ___________ waves.
7. Measuring earthquakes
   1. Seismology, Seismograph, seismogram
   2. The ______________ scale correlates the amplitude of the largest peak on a seismogram during a quake to the amount of energy released by the quake.
      1. measures seismogram wave amplitude
      2. Because each successive whole number corresponds to a 10-fold increase in the amplitude of a seismogram tracing, the Richter scale is said to be ______________.
      3. Earthquake energy: each added Richter whole number represents a 30-fold increase in energy
      4. 9 to 9.5 effective upper limit
      5. A magnitude of ________ or more denotes a major earthquake.
      6. 6.3 = 1 megaton nuclear explosion (50 times more powerful than Hiroshima atomic bomb). About 100 magnitude 6 earthquakes occur per year.
      7.  

Effects

1. Ground shifts
   1. Lateral
   2. Vertical
2. Landslides
   1. Port Royal, Jamaica, 1692
3. The conversion of unconsolidated sediment having some cohesiveness into a mass of flowing, water-saturated sediment is termed ______________.
   1. Turnagain Heights, Alaska, 1964
   2. Nimitz Freeway, Loma Prieta earthquake, 1989
4. The sloshing that occurs in an enclosed body of water following an earthquake is called a(n) ___________.
5. __________ are large coastal waves caused by displacement of the sea floor during an earthquake.
   1. Sea-floor displacement
   2. wave speed up to 500 mph
   3. wave length up to 100 miles
   4. wave height at sea <3 feet
   5. waves extend to bottom of ocean
   6. 1960 tsunami killed 61 in Hawaii and 180 in Japan
6. Fires

Coping with earthquakes

1. Structural stability depends on building design
   1. Strong, flexible earthquake-resistant materials: wood, steel, reinforced concreate (not stucco, adobe, heavy masonry)
2. Ground stability
   1. Damage less over bedrock than over unconsolidated sediment

Prediction

1. Earthquakes may occur virtually anywhere. (Oklahoma earthquake map)
2. Long-term
   1. Probability maps
   2. Seismic _____ refer to locked fault segments that have not experienced seismic activity for a long time.
   3. Tectonic ________ is the nearly constant motion of fault blocks, releasing the strain energy of the fault segments.
3. Short-term
   1. Dilatancy is the increase in volume of stressed rocks as strain energy increases and numerous ___________ appear.
      1. Micro-earthquakes
         1. seismograph by Zhang Heng, A.D. 132.
      2. tilts or buldges in rocks
      3. changes in seismic wave velocity
      4. variations in electrical conductivity
      5. changes in groundwater level and chemistry
   2. Unusual animal behavior
      1. high-pitched sounds emitted by cracking rocks heard by animals
      2. Haicheng, China, 1975.
4. All methods inconsistent
   1. Probability versus particular event
   2. Precursors not always present
   3. Small earthquakes can trigger large earthquakes

Reading Focus Questions

Be prepared to answer any of these questions should they occur on a quiz or on the final exam.

1. Most earthquakes are caused by:
   1. magma moving forcefully through underground caverns
   2. the release of accumulated strain energy in rocks undergoing plastic deformation
   3. the release of accumulated strain energy in rocks undergoing elastic deformation
   4. excess lithostatic pressure on rocks buried deep within the Earth
2. All of the following are correct statements about earthquakes EXCEPT:
   1. An earthquake's focus is the place within the Earth where rocks shift in response to stress.
   2. An earthquake's epicenter is in the exact center of the fault that causes the earthquake.
   3. Aftershocks are smaller earthquakes that occur after a major earthquake.
   4. After an earthquake, rocks along a fault temporarily lock in place and resist further movement, causing earthquakes to be sporadic rather than continuous.
3. All of the following are correct statements about the Richter scale EXCEPT:
   1. the Richter scale measures the amount of damage due to the earthquake
   2. the Richter scale is logarithmic
   3. the Richter scale is objective, measured by a seismograph
   4. the Richter scale measures the size of earthquake waves
4. Earthquakes measuring 5 and 7 on the Richter scale differ in wave amplitude by:
   1. 2 times
   2. 10 times
   3. 100 times
   4. 1000 times
5. Earthquakes measuring 3 and 4 on the Richter scale differ in released energy by:
   1. 3 times
   2. 30 times
   3. 900 times
   4. 27,000 times
6. In order to relieve the stress buildup that would cause a Richter magnitude 7 earthquake, approximately how many magnitude 4 earthquakes would have to occur?
   1. 3
   2. 1000
   3. 27,000
   4. 28
7. The magnitude of most of the Earth's earthquakes is from _______ on the Richter scale.
   1. 1 to 3.5
   2. 3.5 to 4.5
   3. 4.5 to 6
   4. 6 to 9
8. All of the following describe damaging effects of earthquakes EXCEPT:
   1. landslides involving unstable rock, rock fragments, or soil.
   2. liquefaction, which is the release of floodwaters by the destruction of a dam.
   3. seiches, which are oscillations of enclosed bodies of water such as lakes or bays.
   4. fires by rupturing power or gas lines.
9. In an earthquake-prone region, the safest house would be a:
   1. log cabin built on bedrock
   2. log cabin built on loose soil
   3. brick house built on bedrock
   4. brick house built on loose soil
10. The frequency of earthquakes in a specific region can be determined by studies of all of the following EXCEPT:
    1. historical records
    2. mathematical models involving the tectonic stress placed on faults from plate movements.
    3. topographic evidence of faults such as breaks in the landscape, or offset linear valleys.
    4. trenches excavated across a fault-zone.
11. All of the following may be precursors of an imminent earthquake EXCEPT:
    1. swarms of micro-earthquakes
    2. tectonic creep along fault segments
    3. changes in electrical conductivity of rocks
    4. bulges or tilts in surface rocks
12. Animals sometimes display unusual behavior prior to a major earthquake because:
    1. they have unusual psychic abilities
    2. they are able to sense changes in the electrical conductivity of the bedrock
    3. they can hear high-pitched sounds and feel vibrations that occur from the cracking of the bedrock.
    4. they can feel the changes in the atmosphere that occur just prior to an earthquake.