Continuous Lamb-like Waves Observed With Global Seismic Networks

Summary Broadband seismic stations are primarily designed to record ground displacement from earthquakes, but they are sensitive to a wide range of processes, including human activity, oceanic waves, and atmospheric pressure variations. These signals are often considered noise, yet their study at frequencies from a few millihertz to one hertz has been fundamental for understanding geosphere coupling, developing methods to image Earth’s interior, and monitoring climate. At lower frequencies, below 10 cycles per day, the origin of continuous seismic noise remains poorly understood and may result from multiple coexisting mechanisms. To illuminate this part of the spectrum and its governing physics, we apply a dedicated processing method to 20 years of global seismic data. Our approach enables precise quantification of frequencies, angular degrees, and velocities of low-frequency modes, which we unambiguously identify as Lamb waves in the atmosphere.