GLY 150: Earthquakes and Volcanoes Spring 2005: 030105

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GLY 150 Earthquakes and VolcanoesSpring 2005
03/01/05
1999 Chi-Chi, Taiwan Earthquake
Lecture 12
All from http//www.ceri.memphis.edu/taiwan/day4pi
cs.shtml
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AnnouncementsGLY 150 Earthquakes and Volcanoes

• The next journal assignment is due this Thurs.
  If you still have questions regarding the
  grading, I have discussed grading criteria in
  class and with the TA. If you would like your
  journal assignments regraded, please see the TA
  (grading criteria specified in your syllabus)
• Your next HW assignment is on the web. It is due
  next Tuesday,
• Instructor office hours have changed to Mon.
  200-300 and Wed. 200-300. You can always
  make an appoint with me to arrange other times.
• Remember, use your texts to supplement the
  lecture notes, especially as we start case
  studies next week. It will be impossible to
  cover all the material in the text but it will
  appear on exams and its actually interesting.

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Events this QuarterSpring 2005
Note Some of the eruptions may be ongoing so be
sure to check their current status
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Earthquake MagnitudeThe Amount of Energy Released
http//jove.geol.niu.edu/faculty/fischer/105_info/
105_E_notes/lecture_notes/Earthquakes/EQ_part2.htm
l
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Earthquake MeasurementEnergy Release

• Earthquake magnitude scales are logarithmic such
  that a unit increase in magnitude results in a
  roughly 32-fold increase in the amount of energy
  released during the event
• e.g., Richter Magnitude
• Unit increase in magnitude 10x increase in
  amplitude of ground shaking
• Unit increase in magnitude 32x increase in
  energy released

Magnitude Approximate Equivalent TNT Energy
4.0 1010 tons
5.0 31800
tons 6.0
1,010,000 tons 7.0
31,800,000 tons 8.0
1,010,000,000 tons 9.0
31,800,000,000 tons
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Worldwide Seismic Moment ReleaseWhere?

• Most seismic moment/energy release occurs at
  subduction zones

http//www.essc.psu.edu/ammon/HTML/Classes/IntroQ
uakes/Notes/earthquake_size.html
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Largest Measured EarthquakesAll Megathrust Events

• Sumatra
• 2004

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Indian-Asian Collisional ZoneHimalayan Range

• Continental Continental

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Convergent Plate BoundariesContinental Collision
Zones Continent vs. Continent

• Because both are buoyant, neither continental
  plate subducts broad areas of high elevation
  (large mountain ranges and high plateaus) result

Figure in This Dynamic Earth (http//pubs.usgs.gov
/publications/text/historical.html)
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Supercontinent CyclesContinental Collision

• In part, rock uplifted in a continental
  collisional zone comes from sediments deposited
  in the ocean basin located between the continents
  prior to collision
• Rocks in continental collision
• zones are highly deformed
• Magma doesnt reach the
• surface so there is no
• active volcanism

http//jan.ucc.nau.edu/wittke/GLG100/PlateTectoni
cs.html
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India-Asian Collision Zone Faults

• Complexly faulted
• Multiple faults in multiple orientations
• Faults are widely distributed

http//www.brunel.ac.uk/depts/geo/iainsub/studwebp
age/khan/faults-3.jpg
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Formation of the Himalayas and TibetConvergent
Boundary Continental Collision

• Indian subcontinent colliding with Eurasian plate

Both from Dynamic Earth http//pubs.usgs.gov/publ
ications/text/understanding.htmlanchor5798673
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Formation of the Himalayas and TibetConvergent
Boundary Continental Collision
From http//www.pbs.org/wgbh/nova/everest/earth/bi
rthmountains.html
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Formation of the Himalayas and TibetConvergent
Boundary Continental Collision
From http//www.pbs.org/wgbh/nova/everest/earth/bi
rthmountains.html
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Formation of the Himalayas and TibetConvergent
Boundary Continental Collision
From http//www.pbs.org/wgbh/nova/everest/earth/bi
rthmountains.html
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Formation of the Himalayas and TibetConvergent
Boundary Continental Collision
From http//www.pbs.org/wgbh/nova/everest/earth/bi
rthmountains.html
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Formation of the Himalayas and TibetConvergent
Boundary Continental Collision
From http//www.pbs.org/wgbh/nova/everest/earth/bi
rthmountains.html
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Formation of the Himalayas and TibetConvergent
Boundary Continental Collision

• Major shortening and thickening
• Accommodated via thrust faulting

Continental collision is initiated
Mature continental collision zone
Dynamic Earth http//pubs.usgs.gov/publications/t
ext/understanding.htmlanchor5798673
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India-Asian Collision Zone Distribution of
Seismicity
1977-1997 Seismicity

• Seismicity broadly distributed
• Extends great distances from plate boundary
• Localized in some areas, absent in others

http//gldss7.cr.usgs.gov/neis/general/seismicity/
c_asia.html
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Continental Collision ZonesConvergent Boundary
Continental-Continental

• Earthquakes at the interface between the two
  plates
• Shallow, broadly distributed earthquakes in both
  plates due to the intense compression at the
  plate boundary

High hazard in some areas, very low hazard in
other areas
http//seismo.ethz.ch/GSHAP/eastasia/
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The India-Asia Collision ZoneConvergent
Boundary Continental-Continental

• Plate boundary interface
• History of large earthquakes
• Many likely seismic gaps near population centers

http//cires.colorado.edu/bilham/HimHazardScience
.html
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2000 Republic Day Earthquake, Bhuj, India

• Mw 7.7
• Occurred on shallow thrust fault relatively far
  from plate boundary
• At least 20,005 killed 166,836 injured
• 339,000 building destroyed 783,000 damaged
• Many roads and bridges damaged in Gujarat
  Province
• Intraplate earthquake felt over large area
• Seismic waves in Indian subcontinent travel like
  seismic waves in eastern U.S.

http//www.asc-india.org/
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2000 Republic Day Earthquake, Bhuj, India

• Major hazard collapse of unreinforced masonry
  structures, especially in remote villages
• In cities, collapses often the result of
  improper/illegal construction practices

http//www2.rcep.dpri.kyoto-u.ac.jp/7Emori/India/
photos/
The Cities
The Villages
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Quiz
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Quiz 5 Convergent Boundaries

• (1 point) Tsunamis are generated because
• megathrust earthquakes usually break the surface
  on land
• subduction zone faults are thought to be freely
  slipping at depth
• there are shallow earthquakes at subduction zones
• megathrust earthquakes generally break the
  surface under the ocean
• megathrust earthquakes often produce dead forests
• (1 point) Oceanic-Continent collision zones
• can produce earthquakes with magnitudes above 9
• are not located around the Ring of Fire
• produce broad, extensive areas of deformation
• produce no change in elevation in the overriding
  plate
• cannot produce tsunamis
• (2 points) Write 2-3 complete sentences
  discussing concepts you are having difficulty
  with, topics you think are particularly
  interesting, specific questions you might have,
  or topics you want to hear more about, etc.

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Aleutian Subduction Zone,Alaska

• Oceanic - Oceanic

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Convergent Plate BoundariesSubduction Zones
Oceanic vs. Oceanic

• Narrow mountain belts with volcanoes.
• Since they are detached from any continent, these
  mountain belts are called island arcs (e.g. a
  narrow linear chain of volcanic islands).
• The oldest, coldest, densest slab subducts

Figure in This Dynamic Earth (http//pubs.usgs.gov
/publications/text/historical.html)
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Aleutian Arc, AlaskaSeismicity
Different colors represent different depths
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Subduction ZonesBenioff Zones Aleutian Arc

• Note volcanism along island arc

http//geologyindy.byu.edu/faculty/rah/tectonics/S
tudent20Presentations/200020Fall/Brian20Black/a
laskan.htm
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The Aleutian Subduction ZoneConvergent Boundary
Oceanic-Oceanic
http//www.giseis.alaska.edu/Seis/graphics/akseis.
gif
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1964 Prince William Sound, Alaska Earthquake

• Mw 9.2
• Triggered major tsunami
• Major damage in Gulf of Alaska
• Lesser damage in Canada and West Coast of United
  States (15 killed)
• 125 deaths
• 110 from tsunami
• 15 from earthquake
• 311 million in property damage
• Shaking last for 3 minutes

http//gldss7.cr.usgs.gov/neis/eqlists/USA/1964_03
_28.html
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Subduction ZonesDeformation

• Between events
• Thrust boundary is locked (i.e. stuck)
• Coastline is uplifted
• Overriding crust is shortened
• During earthquakes
• Thrust boundary is slipping
• Coastline subsides
• Overriding plate experiences tension

Between Events
Earthquake
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1964 Prince William Sound, Alaska Earthquake

• As with all major subduction zone earthquakes,
• Huge areas of land uplifted
• Huge areas of land subsided

http//www.tulane.edu/sanelson/geol204/eqhazards
risks.htm
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1964 Prince William Sound, Alaska Earthquake

• Vertical displacements over an area of 520,000
  square kilometers
• Maximum uplifts of 11.5 meters other areas
  subsided up to 2.3 meters
• Triggered major tsunami
• Major damage in Gulf of Alaska
• Lesser damage in Canada and West Coast of United
  States (15 killed)
• Maximum wave height 67 meters
• Minor damage along Gulf Coast of Louisiana and
  Texas

Uplifted marine terrace and fault scarp
http//www.ngdc.noaa.gov/seg/mainmeta.shtml also
Fig. 4.21 Pipkin and Trent
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1964 Prince William Sound, Alaska
EarthquakeOther Damage
Landslide Damage

• Landslides in Anchorage (120 km from epicenter)
  caused major damage
• 30 blocks of structures damaged or destroyed
• Schools devastated
• Largest slide 130 acres
• Water, gas, sewer, telephone and electrical
  systems disrupted throughout area
  (infrastructure)
• Fires at Valdez oil terminal
• Liquefaction also a problem

Tsunami Damage
All from http//www.ngdc.noaa.gov/seg/hazard/slide
set/earthquakes/
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Film Clip
The Eruption of Mount Saint Helens
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(No Transcript)
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Bonus Quiz
Is it Spring or Fall Semester?