The Wasatch Fault is a high angle normal fault, dipping steeply to the west. The fault is active today, with at least 19 major earthquakes documented along the fault over the last six thousand years (UGS, 1996). Although there have been no recent large movements along the fault, evidence of potentially catastrophic earthquakes are well preserved in glacial sediments at the mouth of Little Cottonwood Canyon. These fault scarps are so distinctive that they are frequently pictured in geological and geophysical textbooks. They are easily observed from G. K. Gilbert Geologic Park located at the corner of Wasatch Boulevard and Little Cottonwood Road.
Movement along the Wasatch Fault is believed to have begun approximately 20 million years ago. Movement rates are extremely rapid in geologic terms, estimated by the Utah Geological Survey to be as much as 130 feet over approximately 16,000 years (UGS, 1996). That equates to an inch of uplift every 10.25 years, which far exceeds the erosion rate. The good news is that the Wasatch Mountains are getting higher; the bad news is that there is the potential for a devastating earthquake in the Salt Lake Valley. According to the Utah Geological Survey, collectively a large earthquake has occurred along the central portion of the Wasatch Fault once every 350 years. The last large documented earthquake occurred on the Provo segment of the fault approximately 400 years ago.
| The Wasatch Fault is a normal fault dipping steeply to the west. The eastern block is rising relative to the western block, triangular facets have formed where the fault scarp cuts ridge lines |