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GEOG 100--Lecture 14--Earthquakes
 

GEOG 100--Lecture 14--Earthquakes

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GEOG 100--Lecture 14--Earthquakes GEOG 100--Lecture 14--Earthquakes Presentation Transcript

  • Folding, Faulting,and Earthquakes Chapter 9
  • Diastrophism• Folding and faulting causing deformation of Earth’s crust on a large scale is called diastrophism
  • Compression, Tension, and Shearing stresses• Compression is force exerted inward  • Tension is a pulling apart  • Shearing occurs when force is exerted in opposite directions, but parallel to one another 
  • Crustal Fold Structures
  • Crustal Fold Structures• monocline—a one-sided slope
  • Crustal Fold Structures• monocline—a one-sided slope• syncline—a downfold that creates a U-shape
  • Crustal Fold Structures• monocline—a one-sided slope• syncline—a downfold that creates a U-shape• anticline—an upfold that creates an n-shape
  • Crustal Fold Structures• monocline—a one-sided slope• syncline—a downfold that creates a U-shape• anticline—an upfold that creates an n-shape• overturned fold—similar to an anticline, but tipped to one side
  • Crustal Fold Structures• monocline—a one-sided slope• syncline—a downfold that creates a U-shape• anticline—an upfold that creates an n-shape• overturned fold—similar to an anticline, but tipped to one side• overthrust fold—an overturned fold pushed completely over on its side, so that the entire fold lays on top of the section in front of it
  • FaultsEventually, even the plastic crust will break…
  • Normal Fault(tension stress)
  • Fault Block Mountains The Sierra Nevadas
  • Reverse Fault(compression stress)
  • Strike-slip/Transform/Transcurrent Fault (shear stress)
  • The San Andreas runs rightthrough the town of Hollister, CA…
  • Common Structures Associated with Transform Faults
  • Thrust Fault(compression stress—low-angle)
  • Earthquakes or Hypocenter
  • Earthquake Measurement
  • Earthquake Measurement Seismic waves—Energy waves propagated during an earthquake
  • Earthquake Measurement Seismic waves—Energy waves propagated during an earthquake Seismograph—Recording device for measuring the amount of shaking which occurs during an earthquake
  • Earthquake Measurement Seismic waves—Energy waves propagated during an earthquake Seismograph—Recording device for measuring the amount of shaking which occurs during an earthquake Seismogram—The printed record made by the seismograph
  • Quantitative vs. Qualitative Seismic Measurements
  • Quantitative vs. Qualitative Seismic Measurements
  • Quantitative vs. Qualitative Seismic Measurements• Quantitative—Objective, fact-based measurement; mathematical
  • Quantitative vs. Qualitative Seismic Measurements• Quantitative—Objective, fact-based measurement; mathematical
  • Quantitative vs. Qualitative Seismic Measurements• Quantitative—Objective, fact-based measurement; mathematical• Qualitative—Subjective; each person’s interpretation of the same event may be different
  • Measuring Seismic Waves
  • Measuring Seismic Waves• Richter Scale—A numerical expression of the amount of energy released during an earthquake event (Quantitative)
  • Measuring Seismic Waves• Richter Scale—A numerical expression of the amount of energy released during an earthquake event (Quantitative) – Based on the physical force exerted by the surface movement of earthquake waves
  • Measuring Seismic Waves• Richter Scale—A numerical expression of the amount of energy released during an earthquake event (Quantitative) – Based on the physical force exerted by the surface movement of earthquake waves – Logarithmic scale…the difference between one order of magnitude and the next represents 10 times the amount of force
  • Measuring Seismic Waves• Richter Scale—A numerical expression of the amount of energy released during an earthquake event (Quantitative) – Based on the physical force exerted by the surface movement of earthquake waves – Logarithmic scale…the difference between one order of magnitude and the next represents 10 times the amount of force – Only useful for expressing surface motion
  • Measuring Seismic Waves• Richter Scale—A numerical expression of the amount of energy released during an earthquake event (Quantitative) – Based on the physical force exerted by the surface movement of earthquake waves – Logarithmic scale…the difference between one order of magnitude and the next represents 10 times the amount of force – Only useful for expressing surface motion – Equations not accurate enough at high magnitude
  • Measuring Seismic Waves
  • Measuring Seismic Waves• Moment Magnitude Scale
  • Measuring Seismic Waves• Moment Magnitude Scale – More accurate at higher magnitudes
  • Measuring Seismic Waves• Moment Magnitude Scale – More accurate at higher magnitudes – Equations used to compare larger quakes (>4.0)--best for 7.0+ (Quantitative)
  • Measuring Seismic Waves• Moment Magnitude Scale – More accurate at higher magnitudes – Equations used to compare larger quakes (>4.0)--best for 7.0+ (Quantitative) – Based on:
  • Measuring Seismic Waves• Moment Magnitude Scale – More accurate at higher magnitudes – Equations used to compare larger quakes (>4.0)--best for 7.0+ (Quantitative) – Based on: • the size and extent of fault movement
  • Measuring Seismic Waves• Moment Magnitude Scale – More accurate at higher magnitudes – Equations used to compare larger quakes (>4.0)--best for 7.0+ (Quantitative) – Based on: • the size and extent of fault movement • the amount of stress necessary to overcome the friction holding the rocks together
  • Measuring Seismic Waves• Moment Magnitude Scale – More accurate at higher magnitudes – Equations used to compare larger quakes (>4.0)--best for 7.0+ (Quantitative) – Based on: • the size and extent of fault movement • the amount of stress necessary to overcome the friction holding the rocks together • and the average distance that the rocks slid apart along the fault.
  • Measuring Seismic Waves
  • Measuring Seismic Waves• Mercalli Scale
  • Measuring Seismic Waves• Mercalli Scale – Measures an earthquake’s intensity (Qualitative)
  • Measuring Seismic Waves• Mercalli Scale – Measures an earthquake’s intensity (Qualitative) – Based on what people feel
  • Measuring Seismic Waves• Mercalli Scale – Measures an earthquake’s intensity (Qualitative) – Based on what people feel – Uses questionnaires and personal accounts
  • Measuring Seismic Waves• Mercalli Scale – Measures an earthquake’s intensity (Qualitative) – Based on what people feel – Uses questionnaires and personal accounts • Good for:
  • Measuring Seismic Waves• Mercalli Scale – Measures an earthquake’s intensity (Qualitative) – Based on what people feel – Uses questionnaires and personal accounts • Good for: – Earthquakes of the past for which no other records exist
  • Measuring Seismic Waves• Mercalli Scale – Measures an earthquake’s intensity (Qualitative) – Based on what people feel – Uses questionnaires and personal accounts • Good for: – Earthquakes of the past for which no other records exist – Areas where existing development makes geologic studies more difficult
  • Measuring Seismic Waves• Mercalli Scale – Measures an earthquake’s intensity (Qualitative) – Based on what people feel – Uses questionnaires and personal accounts • Good for: – Earthquakes of the past for which no other records exist – Areas where existing development makes geologic studies more difficult – Can help urban agencies plan for future earthquakes in areas needing upgrades or retrofitting
  • Loma Prieta Quake, 1989
  • Loma Prieta Quake
  • Loma Prieta Quake• On October 17, 1989, at 5:04:15 p.m. (PDT)
  • Loma Prieta Quake• On October 17, 1989, at 5:04:15 p.m. (PDT)• Magnitude 6.9 (moment magnitude)
  • Loma Prieta Quake• On October 17, 1989, at 5:04:15 p.m. (PDT)• Magnitude 6.9 (moment magnitude)• Severely shook the San Francisco and Monterey Bay regions
  • Loma Prieta Quake• On October 17, 1989, at 5:04:15 p.m. (PDT)• Magnitude 6.9 (moment magnitude)• Severely shook the San Francisco and Monterey Bay regions• Epicenter located near Loma Prieta peak in the Santa Cruz Mountains, approximately 14 km (9 mi) NE of Santa Cruz and 96 km (60 mi) S-SE of San Francisco
  • Loma Prieta Quake• On October 17, 1989, at 5:04:15 p.m. (PDT)• Magnitude 6.9 (moment magnitude)• Severely shook the San Francisco and Monterey Bay regions• Epicenter located near Loma Prieta peak in the Santa Cruz Mountains, approximately 14 km (9 mi) NE of Santa Cruz and 96 km (60 mi) S-SE of San Francisco• The Pacific and North American Plates abruptly slipped as much as 2 meters (7 ft) along the San Andreas fault
  • Loma Prieta Quake• On October 17, 1989, at 5:04:15 p.m. (PDT)• Magnitude 6.9 (moment magnitude)• Severely shook the San Francisco and Monterey Bay regions• Epicenter located near Loma Prieta peak in the Santa Cruz Mountains, approximately 14 km (9 mi) NE of Santa Cruz and 96 km (60 mi) S-SE of San Francisco• The Pacific and North American Plates abruptly slipped as much as 2 meters (7 ft) along the San Andreas fault• The rupture began at a depth of 18 km (11 mi) and extended 35 km (22 mi) along the fault, but it did not break the surface of the Earth
  • Loma Prieta Quake, 1989
  • Seismic Waves
  • Seismic Waves• Body waves
  • Seismic Waves• Body waves – Travel deep beneath the surface
  • Seismic Waves• Body waves – Travel deep beneath the surface • P-waves
  • Seismic Waves• Body waves – Travel deep beneath the surface • P-waves • S-waves
  • Seismic Waves• Body waves – Travel deep beneath the surface • P-waves • S-waves• Surface waves
  • Seismic Waves• Body waves – Travel deep beneath the surface • P-waves • S-waves• Surface waves – Travel at or near the surface
  • Seismic Waves• Body waves – Travel deep beneath the surface • P-waves • S-waves• Surface waves – Travel at or near the surface • L-waves
  • Seismic Waves• Body waves – Travel deep beneath the surface • P-waves • S-waves• Surface waves – Travel at or near the surface • L-waves • R-waves
  • Seismic Waves P-waves: Pressure or Primary waves  Travel fastest  First to arrive  Travel through all mediums (solid, liquid, gas)  If big enough, they can be felt on the other side of the planet
  • Seismic Waves P-waves: Pressure or Primary waves  Travel fastest  First to arrive  Travel through all mediums (solid, liquid, gas)  If big enough, they can be felt on the other side of the planet
  • Seismic Waves S-waves: Secondary or Shear waves  Slower than P-waves  Second to arrive  Travel only through solids
  • Seismic Waves S-waves: Secondary or Shear waves  Slower than P-waves  Second to arrive  Travel only through solids
  • Seismic Waves S-waves: Secondary or Shear waves  Slower than P-waves  Second to arrive  Travel only through solids
  • Seismic Waves• Love waves – Push rocks from side to side as the motion of the wave follows a horizontal ellipse which travels forward
  • Seismic Waves• Rayleigh waves produce an up and down motion created by a forward roll, much like that of an oscillating water wave on the open ocean – Slower than Love waves • 10 times the speed of sound
  • Both L-waves and R-waves:
  • Both L-waves and R-waves:• Can travel only through solids
  • Both L-waves and R-waves:• Can travel only through solids• May not be felt at every earthquake event
  • Both L-waves and R-waves:• Can travel only through solids• May not be felt at every earthquake event• Motion decreases exponentially the further the focus is from the surface
  • Both L-waves and R-waves:• Can travel only through solids• May not be felt at every earthquake event• Motion decreases exponentially the further the focus is from the surface• Motions do not dissipate quickly
  • Both L-waves and R-waves:• Can travel only through solids• May not be felt at every earthquake event• Motion decreases exponentially the further the focus is from the surface• Motions do not dissipate quickly• May continue for an extended period at the tail end of a quake
  • Both L-waves and R-waves:• Can travel only through solids• May not be felt at every earthquake event• Motion decreases exponentially the further the focus is from the surface• Motions do not dissipate quickly• May continue for an extended period at the tail end of a quake• Can travel much longer distances than body waves
  • Both L-waves and R-waves:• Can travel only through solids• May not be felt at every earthquake event• Motion decreases exponentially the further the focus is from the surface• Motions do not dissipate quickly• May continue for an extended period at the tail end of a quake• Can travel much longer distances than body waves• Tend cause the most damage to structures and to landforms prone to mass movement
  • Earthquakes and theRelationship to Plate Tectonics
  • Pinpointing an Earthquake
  • Pinpointing an Earthquake
  • Earthquake Hazard Map
  • Earthquake Hazards
  • Earthquake Hazards• Falling debris and rock material
  • Earthquake Hazards• Falling debris and rock material• Crumbling buildings
  • Earthquake Hazards• Falling debris and rock material• Crumbling buildings• Ground cracks
  • Earthquake Hazards• Falling debris and rock material• Crumbling buildings• Ground cracks• Broken bridges
  • Earthquake Hazards• Falling debris and rock material• Crumbling buildings• Ground cracks• Broken bridges• Landslides
  • Earthquake Hazards• Falling debris and rock material• Crumbling buildings• Ground cracks• Broken bridges• Landslides• Liquefaction
  • Earthquake Hazards• Falling debris and rock material• Crumbling buildings• Ground cracks• Broken bridges• Landslides• Liquefaction• Tsunamis
  • Liquefaction
  • Liquefaction• Liquefaction
  • Liquefaction• Liquefaction – (from Latin liquefacere meaning “to liquefy”)
  • Liquefaction• Liquefaction – (from Latin liquefacere meaning “to liquefy”) – Settling of solid material and rising of water normally stored between the pore spaces, turning surface material into quicksand
  • Liquefaction• Liquefaction – (from Latin liquefacere meaning “to liquefy”) – Settling of solid material and rising of water normally stored between the pore spaces, turning surface material into quicksand – Danger where the water table is near the surface and surface material consists of loose, unconsolidated, water-saturated sediments
  • Liquefaction• Liquefaction – (from Latin liquefacere meaning “to liquefy”) – Settling of solid material and rising of water normally stored between the pore spaces, turning surface material into quicksand – Danger where the water table is near the surface and surface material consists of loose, unconsolidated, water-saturated sediments • Land may subside
  • Liquefaction• Liquefaction – (from Latin liquefacere meaning “to liquefy”) – Settling of solid material and rising of water normally stored between the pore spaces, turning surface material into quicksand – Danger where the water table is near the surface and surface material consists of loose, unconsolidated, water-saturated sediments • Land may subside • Structures (and people!) sink
  • Liquefaction• Liquefaction – (from Latin liquefacere meaning “to liquefy”) – Settling of solid material and rising of water normally stored between the pore spaces, turning surface material into quicksand – Danger where the water table is near the surface and surface material consists of loose, unconsolidated, water-saturated sediments • Land may subside • Structures (and people!) sink – Only occurs during shaking
  • Liquefaction• Liquefaction – (from Latin liquefacere meaning “to liquefy”) – Settling of solid material and rising of water normally stored between the pore spaces, turning surface material into quicksand – Danger where the water table is near the surface and surface material consists of loose, unconsolidated, water-saturated sediments • Land may subside • Structures (and people!) sink – Only occurs during shaking • After shaking, settled material becomes solid again and any water on the surface either percolates back down or runs off into streams.
  • Liquefaction
  • Liquefaction under Kawagishi-cho apartment buildings, Niigata quake, 1964
  • San Francisco: Original Shoreline Liquefaction Potential?
  • The Pacific Ring of Fire
  • The Pacific Ring of Fire
  • Oceanic-Oceanic Subduction
  • Oceanic-Oceanic SubductionProduces: – Big earthquakes and volcanic islands – A deep ocean trench
  • What Does a Tidal Wave Look Like?
  • What Does a Tidal Wave Look Like? Truro, Nova Scotia, Canada
  • You meant a Tsunami, right?
  • You meant a Tsunami, right?
  • You meant a Tsunami, right?
  • Oceanic-Oceanic SubductionProduces: – Big earthquakes and volcanic islands, called “island arcs” – A deep ocean trench – High potential for tsunamis
  • Tsunamis
  • Tsunamis• Waves caused by undersea volcanic or tectonic events (earthquakes)
  • Tsunamis• Waves caused by undersea volcanic or tectonic events (earthquakes)• Unnoticed by observers on the open ocean
  • Tsunamis• Waves caused by undersea volcanic or tectonic events (earthquakes)• Unnoticed by observers on the open ocean• Can reach up to 100 feet in height when they enter a coastal zone
  • Tsunamis• Waves caused by undersea volcanic or tectonic events (earthquakes)• Unnoticed by observers on the open ocean• Can reach up to 100 feet in height when they enter a coastal zone• Can be anticipated wherever deep-focus undersea earthquakes occur
  • Tsunamis• Waves caused by undersea volcanic or tectonic events (earthquakes)• Unnoticed by observers on the open ocean• Can reach up to 100 feet in height when they enter a coastal zone• Can be anticipated wherever deep-focus undersea earthquakes occur• Can be detected with special sensors, allowing time for evacuation
  • Sumatra Quake, Dec. 26, 2004http://www.nytimes.com/packages/khtml/2004/12/26/ international/20041227_QUAKE_FEATURE.html