Warm Up 11/1

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Warm Up 11/1

• Which of the following is NOT a characteristic of
  S waves?
• a. They cannot be transmitted through water or
  air.
• b. They shake particles at right angles to the
  direction the waves travel.
• c. They travel more slowly than P waves.
• d. They temporarily change the volume of
  material by compression and expansion.
• The trace that records an earthquake from seismic
  instruments is called a ____.
• a. richtergram c. seismogram
• b. seismograph d. magnitude
• The distance between a seismic station and the
  earthquake epicenter is determined from the ____.
  
• a. measurement of the amplitude of the surface
  wave
• b. calculation of the earthquake magnitude
• c. arrival times of P and S waves
• d. intensity of the earthquake
• Answers 1) d. 2) c. 3) c.

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Destruction from Earthquakes

• Chapter 8, Section 3

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Seismic Vibrations

• The damage to buildings and other structures from
  earthquakes depends on several factors. The
  three factors include the intensity and duration
  of the vibrations, the nature of the material on
  which the structure is built, and the design of
  the structure.
• Engineers have learned that unreinforced stone or
  brick buildings are the most serious safety
  threats during earthquakes
• Liquefaction loosely consolidated sediments are
  saturated with water and turned into a liquid
  that is not able to support buildings

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Seismic Damage
Liquefaction Niigata, Japan 1964
Ground Shaking Loma Prieta, CA 1989
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Concept Check

• When does liquefaction occur?
• When loosely consolidated soils saturated with
  water are shaken by earthquake waves

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Tsunamis

• Tsunamis A large water wave caused by seismic
  waves
• A tsunami triggered by an earthquake occurs where
  a slab of the ocean floor is displaced vertically
  along a fault
• A tsunami also can occur when the vibration of a
  quake sets an underwater landslide into motion
• A tsunami can travel across the ocean at a speed
  of 500-950 km/hr
• When the wave enters shallow coastal waters, it
  will slow down and begin piling on top of itself
  to reach a height sometimes greater than 30 meters

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Tsunamis
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Tsunami Travel Time to Honolulu
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Indonesia Tsunami 2004
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Indonesia Tsunami 2004
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Concept Check

• At what point does the tsunami gain the most
  height?
• When it enters shallow waters

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Other Dangers

• The greatest damage to structures is from
  landslides and ground subsidence, or the sinking
  of the ground triggered by vibrations
• The violent shaking can cause water and gas lines
  to rupture
• Fire is also a threat, as witnessed by the
  large-scale destruction of San Francisco when
  their gas and electric lines were cut along with
  the water lines needed to put out the fires

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Other Dangers
Landslide Turnnagin Heights, Alaska, 1964
Fire San Francisco, 1906
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Predicting Earthquakes

• The goal of short-range prediction is to provide
  an early warning of the location and magnitude of
  a large earthquake
• Methods for short-range predictions of
  earthquakes have NOT been successful
• Long-range predictions give the probability of a
  certain magnitude earthquake occurring within 30
  to 100-plus years
• Seismic gap an area along a fault where there
  has not been any earthquake activity for a long
  period of time
• Scientists dont yet understand enough about how
  and where earthquakes will occur to make accurate
  long-term predictions

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Probability of Earthquakes Along the San Andreas
Fault
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Shaking Hazard for Southern California
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Assignment

• Read Chapter 8, Section 3 (pg. 229-232)
• Do 8.3 Assessment 1-6 (pg. 232)