Quake may be overdue
If one Utah State University professor’s hunch is right, the Wasatch Front may be due for an earthquake.
“There is a 30 percent chance of having an earthquake along the Wasatch Front in the next 50 years,” said USU geology professor Jim Evans.
The last major earthquake on the Wasatch Front was between 400 and 550 years ago, north of Nephi.
Evans said geologists determine the age of faults by studying the layered sequence of rock in the earth.
A fault will cause a slip in the sediment. A 500-year-old layer may slip down and be covered by more sediment. Where there is a discrepancy in layering, the age of the fault can be determined.
This is how geologists know Cache Valley experiences a major quake every 4,000 to 7,000 years.
The nearest segment of the Wasatch Fault is near Brigham City, and were an earthquake to happen there, even the Wellsville Mountains wouldn’t be enough to keep Cache Valley residents from feeling it, Evans said.
The degree of damage from an earthquake depends on four factors: the distance from the focus of the quake inside the earth, the local geologic conditions, the size and type of earthquake and buildings on the location.
Generally, valleys are more susceptible to damage in earthquakes than hills are, due to softer sediments. Of course, smaller buildings are safer than skyscrapers and tall apartment buildings, Evans said.
According to seismic information from the University of Utah, about 700 earthquakes occur in Utah every year, 2 percent of which can be felt.
Five hundred of Utah’s earthquakes occur along the Wasatch Front. Were a “direct hit” to occur to the Wasatch Front, a magnitude 5.5 quake could cause around $830 million in damages.
A magnitude 6.5 quake could cause $6.5 billion in damages.
The last earthquake over magnitude 5.0 to strike Cache Valley occurred Aug. 30, 1962, and measured 5.7 on the Richter Scale.