As Hurricane Irma churns through the Caribbean, it’s packing winds 185 mph winds and gusts up to 225. The Category 5 hurricane is so powerful, it’s registering on equipment used to measure earthquakes.

“Considering the strength of the winds, it’s not surprising at all to see a hurricane of this size being recorded on our seismometers,” said John Bellini.

Bellini is a geophysicist at the National Earthquake Information Center in Golden. It’s his job to make sense of the squiggly lines recorded by seismometers.

“What we’re looking at here is a magnitude 3.7 aftershock from the Idaho earthquake that occurred this past Saturday,” Bellini said, pointing to seismometer recordings on his computer screen.

It’s the bigger squiggly lines that capture Bellini’s attention. The smaller ones he tends to ignore.

“In general, it’s just something in the background that we really don’t really pay much attention to,” Bellini explained.

Seismometers can pick up small vibrations in the ground caused by human activity like mining, farming and construction. Strong winds and swaying trees can register as noise on seismometers, too. On Wednesday, a U.S. Geological Survey seismometer on the Leeward Islands of Antigua and Barbuda registered vibrations from Hurricane Irma.

“You can see that the noise does increase in size and amplitude,” Bellini said, pointing to the recording taken from the USGS station.

The waveform from the seismometer intensifies and suddenly stops about the time Hurricane Irma passed over the islands early Wednesday. Bellini suspects Irma may have damaged the station and cut off communication.

Hurricane Irma may only show up as noise on a seismometer, but it’s gotten Bellini’s attention.

“This one I’m paying some attention to because I have family that’s in South Florida,” he said.

Bellini is closely tracking Irma’s path and trusting his family will take precautions in case the storm makes landfall.

“I think they’re planning on evacuating,” he said. “They’ve been through [hurricanes] before so they know what they need to do.”