Detection and characterization of resonant signals in global seismology: Evidence for shallow fluid reservoirs and their interaction with the oceans

Using a new global seismological analysis technique designed to detect long-lasting coherent signals, we identify both previously known and entirely unrecognized resonant-like seismic emissions at periods longer than 10 seconds. A detailed examination of these signals allows us to locate their sources with remarkable precision. Strikingly, they cluster in offshore sedimentary basins near major river fans and beneath ice-covered regions. Although their resonant character resembles classic volcanic tremor, the source locations indicate that they are not associated with any known volcanic system.

A careful analysis of their frequency content, spatial distribution, and radiation patterns instead suggests that these signals may originate from the resonance of fluids within shallow subsurface reservoirs. This interpretation aligns with the presence of large volumes of gas, oil, and water in thick sedimentary basins, and with seafloor seepage structures that release substantial amounts of naturally generated fluids from depths of roughly 5–10 km.

By tracking the temporal evolution of these signals, we also identify a pronounced seasonal modulation that mirrors oceanic variability. This observation points to a significant coupling between the oceans and the solid Earth, potentially mediated by static or dynamic stress transfer.

The detection of these newly recognized signals opens a promising path toward probing the largely unexplored dynamics of sedimentary layers and their sensitivity to external environmental forcing. More broadly, these findings introduce a new class of geophysical observables capable of revealing how the shallow lithosphere responds to, and interacts with, oceanic processes on seasonal to long-term timescales.