On January 15, 2022 the great volcanic explosion at the Hunga-Tonga–Hunga-Hua’apai Island in the South Pacific sent atmospheric Lamb waves \(A_n\) around the Earth in all directions. The Lamb wave \(A_1\) caused clearly observable disturbances on barometers, seismic sensors, and also gravimeters. We show these disturbances on barometers (with a peak-to-peak amplitude of 2.3 hPa) and the superconducting gravimeters (SG) iOSG-023 and OSG-056 at the stations J9 and BFO (57 km to the east), respectively. We subsequently model these disturbances in gravity using very simple physics-based models. It turns out that the inertial accelerations due to ground displacement by the pressure loading are very important in this case as already shown by Imanishi (Earth Planets Space 74:54, 2022 https://doi.org/10.1186/s40623-022-01615-4) for the SG in Matsushiro, Japan. This inertial effect is almost twice as large at J9 than at BFO, while the pressure pulses have about equal amplitudes. This must with high probability be blamed to the higher deformability of the upper layers of the crust at J9 with soft fluvial sediments on the top compared to BFO where granites and gneisses make up the rocks near the surface.
