Seismotectonics of the Wasatch Fault Zone

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Seismotectonics of the Wasatch Fault Zone

• Haiyan Fu
• Dina Freedman
• 8.30.11

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The Wasatch Fault

• The Wasatch Fault is a normal active fault
• Transition between from the Basin and Range
  province to the Colorado Plateau
• Visible below the highest shoreline of Lake
  Bonneville

Figure 1 The Wasatch Fault visible near American
Fork Canyon (UGS)
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Earthquakes and Utah

• The Wasatch Fault is Aseismic
• Probability of an earthquake Mgt7.5 is 25 during
  the next century

Figure 2 The past 6000 years show 19
surface-faulting earthquakes (UGS, 1996)
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Earthquakes

• Earthquakes in Utah are common
• Last major quake on the SL segment was 1200 YA
• On the Wasatch Fault, an earthquake in Herriman
  in 1992 was a magnitude 4.3
• The time between earthquakes or clock is unknown

Figure 3 Earthquakes in Utah (Chang and Smith,
2002)
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Flooding Consequences

• Chang and Smith (1998) - flooding from the GSL
  would likely occur with a normal fault earthquake
• It could displace the lakeshore southward up to
  3.5 miles
• Not only flood danger exists but soil
  liquefaction extending 100 miles from the center
  of a M 7.5 quake (USGS, 1996)

Figure 5 Effects of a 2 meter slip and a lake
level rise to 4212 in SLC on flooding. Adapted
from Chang and Smith, 1998.