Utah Researchers Diagnose Man-made Earthquakes
Around 700 earthquakes shake Utah each year, although only about a dozen are big enough to be felt. Most are natural, but humans can cause earthquakes, too. Recently, in Texas, Oklahoma, and Arkansas, earthquake frequencies have increased around deep-well injection sites, where millions of gallons hydraulic fracturing fluid is pumped deep into the Earth’s crust.
“But here in Utah, we also have induced earthquakes, and they’re sort of the opposite of the earthquakes that are induced by fluid injection, and that’s because they’re related to the extraction of mass," said Dr. Keith Koper, director of the University of Utah Seismograph Stations. "So instead of injecting something extra into the Earth, we’re actually extracting coal.”
Dr. Koper studies earthquakes, and says his research team has found a new way to diagnose whether an earthquake is natural or man-made. Seismometers can measure earthquakes in different ways. The Richter Scale uses amplitude to tell us the size of the earthquake, and the Duration Magnitude tells us how long the quake lasted. By comparing these two numbers, researchers can determine if an earthquake was likely induced by human activity.
“Induced earthquakes are happening very close to the Earth’s surface, they’re very shallow, and it tends to make the waves from the earthquake last longer," said Koper.
Shallower earthquakes with longer durations tend to be more destructive than deeper ones, so this new method of measuring earthquakes could be useful for mining operations as they attempt to reduce the risk of a dangerous quake.
“It demonstrates that if you understand it, you can for the most part control it and still have your economic development carry on," said Koper.