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.