About five years ago, Doug Wiens, a seismologist from Washington University in St. Louis, went knocking on the doors of farmers in Minnesota and Wisconsin. He asked them if they would let him and his team of geologists place seismometers, devices that measure the earth’s movements, on their land.
The farmers were a little suspicious.
“‘Why are you doing this here? Are you exploring for oil? Nobody’s done anything like this before,’” Wiens recalled them asking. “And so, we would show them this gravity map and we’d say, ‘Well, there’s this really unusual feature here and we want to study that.’”