by Nancy Carruthers

8TH-GRADE INTEGRATED SCIENCE
Standard 2, Objective 4 a.
Describe how energy from the
Earth’s interior causes changes to
Earth’s surface.

Is it possible to predict when or where the next large earthquake in Utah will take place? To examine this question further read the two articles in the January 2007 Survey Notes (pdf) that discuss research being conducted on the Wasatch fault.

5TH-GRADE SCIENCE
Standard 2, Objective 2
c. Describe how volcanoes,
earthquakes, and uplift change landforms.
d. Cite examples of how technology
is used to predict volcanoes and
earthquakes.

The Utah Geological Survey (UGS), in conjunction with the U.S. Geological Survey and other researchers, performs studies to determine the timing, frequency, and magnitude of large, prehistoric, surface-faulting earthquakes on the Wasatch fault and other active faults in Utah.

The Wasatch fault, comprising 10 segments that rupture independently, is the longest active normal fault in the United States. Its five central segments extend through the Wasatch Front urban corridor between Brigham City and Nephi.

During the past 10,000 years at least 25 surface-faulting earthquakes have taken place on the Wasatch fault. In Utah, earthquakes that rupture the ground surface are in the magnitude range of 6.5 to 7.5. The amount of time between large surface-faulting earthquakes on the Wasatch fault averages about 300-400 years.

In the two Wasatch fault articles, learn how geologists study large prehistoric earthquakes by measuring topographic profiles and excavating trenches across fault scarps.

The information obtained in these types of studies has given researchers tremendous insights into the location, timing, and magnitude of past surface-faulting earthquakes in Utah, and on the Wasatch fault in particular. Knowledge of past earthquake behavior helps us understand the risks associated with future earthquakes, but scientists remain unable to specifically predict the timing and magnitude of future earthquakes at a given location.

Residents of earthquake-prone areas such as Utah should become familiar with the earthquake risk where they live, take appropriate emergency-planning measures, and not be surprised when “the big one” happens.

For more information on earthquake hazards in Utah, visit our Earthquakes & Geologic Hazards web page.

Possible Discussion Points

What causes earthquakes?

How can large earthquakes change landforms?

What are two methods discussed in these articles that provide data on large prehistoric earthquakes?

What dating method was used to determine the timing of a large prehistoric earthquake at Santaquin?

How does movement on a normal fault (like the Wasatch fault) differ from movement on a strike-slip fault (like the San Andreas fault in California)?