Acoustic waves produced by aircraft in flight cause vibrations in the ground beneath, converting sound energy into ground movement that seismic sensors can capture.
In contrast to earlier research that used seismometers to monitor aircraft, the team advanced this study by pinpointing particular source frequencies in the seismic data that corresponded to various types of aircraft.
The researchers were able to differentiate between the frequencies produced by piston, turboprop, jet, and helicopter aircraft.
Even though we can see clear signatures of aircraft in the data, it is still amazing to realize that the acoustic waves emitted by planes from kilometers up in the sky can move the ground. And these data are good enough to determine the flight parameters and the aircraft source frequencies.
Isabella Seppi, University of Alaska Fairbanks
“In one case, we could detect the subtle difference in RPM [revolutions per minute] for a propeller plane ascending on a flightseeing tour of Denali versus descending,” added Seppi.
Todd Rust, the proprietor of K2 Aviation, located in Talkeetna, Alaska, verified the consistent fluctuations in RPM throughout the specific flightseeing tour observed by the team in their seismic data.
The researchers utilized information gathered from 303 seismic sensors during February and March of 2019. These sensors were strategically positioned along the Parks Highway in central Alaska, spanning the area between Nenana and Talkeetna.
We were aware that these sensors, like microphones, could pick up signals from aircraft. And we know that Alaska is an exceptionally quiet place with exceptionally interesting aircraft, so it seemed like a great realm to explore.
Isabella Seppi, University of Alaska Fairbanks
Seppi and team assessed flight parameters for 1216 identified flights across 48 different aircraft types. The team successfully validated their estimates by utilizing the ground-truth data set of flight paths from Flightradar 24, which included flights in Alaska that traversed the seismic array over a two-month period.
Seppi mentioned that the sensors operated at high sample rates, enabling the researchers to detect the high-frequency signals produced by the aircraft.
An optimal sensor to record an aircraft is probably one that is installed right at the ground surface. Ours were installed into frozen ground, many under the snowpack.
Isabella Seppi, University of Alaska Fairbanks
Seppi and team suggest that their research may provide seismologists with a method to eliminate the interference caused by aircraft signals in seismic data used for earthquake monitoring. The scientists could leverage this data to assess the effects of aircraft noise on both wildlife and human populations in particular areas.
The researchers indicate in the study that with a more established seismic network and analytical techniques such as machine learning, the seismic methodology could potentially identify specific flight routes and types of aircraft, even in adverse weather conditions or in environments characterized by significant acoustic noise.
Journal Reference
Seppi. I. et al. (2025) Classification of Aircraft Types Using Seismic Data in Alaska. The Seismic Record. DOI:10.1785/0320250035.