Mark Petersen, a geologist studying man-made earthquakes, spoke to Northwestern students and faculty Friday to explain how human activity has brought frequent tremors to parts of the country that, until recently, rarely shook.

The culprit, Petersen and his team at the United States Geological Survey argue in a report released Monday, is injection wells, which are used to pump wastewater as deep as two miles below the earth’s surface. The weight of that water can put pressure on nearby faults and trigger earthquakes, Petersen said.

He said the result has been a steep increase in seismic activity in places that do not commonly experience earthquakes, such as Oklahoma. In that state, companies use injection wells to dispose of wastewater they generated through hydraulic fracturing, or fracking, he said. Before 2009, Oklahoma had one or two sizable earthquakes per year, Petersen said. In 2015, the state recorded more than 900.

“These areas have become lit up with seismicity,” Petersen said.

Petersen said he identified 21 areas around the country — from Dallas to Youngstown, Ohio — where research has shown human activity is inducing earthquakes.

The silver lining, Petersen said, is that since people are the ones causing the earthquakes, they can also manage them by moving injection wells away from populated areas and finding ways to pump water without aggravating underground faults.

“People should just consider that,” Petersen said. “But they can’t consider it if they don’t realize there’s a problem to begin with, and I feel like people just haven’t been discussing this very much.”

But Petersen told The Daily the real reason he spent his Friday afternoon explaining his research findings to a group of about 30 students and faculty in Technological Institute is because he hopes to work with NU researchers on mapping earthquake hazards.

“We feel like Northwestern professors have expertise in many of the different areas we need for our modeling,” Petersen said.

Petersen was invited to speak by Earth and Planetary Sciences Prof. Seth Stein, who introduced him as a “seismic celebrity” because of the attention Petersen’s findings have generated since their release.

“The department has had a longstanding interest in natural hazards research,” Stein said. “One of the things we’re trying to understand is how do you make better earthquake hazard maps, but the other thing we’re really interested in is, how do you use this information to make better policies?”

Grace Andrews, a PhD student studying climate change, said she probably will not be one of the students who ends up working with Petersen to model earthquakes, but she said she is glad she came to hear him speak anyway.

“It doesn’t impact my research, but it influences humans,” Andrews said. “I’m interested in the human dynamic of how modern fracking influences people and their lives.”

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Twitter: @NicolasFuRivero