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Seismotectonics of the Wasatch Fault Zone
Haiyan Fu
Dina Freedman
8.30.11
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)
Earthquakes and Utah
• The Wasatch Fault is “Aseismic”• Probability of an earthquake M>7.5 is 25% during the
next century
Figure 2: The past 6000 years show 19 surface-faulting earthquakes (UGS, 1996)
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)
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.