Numerical modeling predicts seismic resonances in the magma chamber-conduit system due to wavefield capturing

In this study we utilize 3D numerical models to simulate seismic resonances in a volcanic edifice, arising from the interaction between an externally excited wavefield and a magma chamber-conduit system. The resultant wavefield holds the potential to provide significant insights into the properties of the magmatic system. Contrary to previous assumptions that required an internal source, our findings show that the magma chamber and conduit efficiently capture the incident wavefield of both P- and S-waves, excited by a high-frequency (~10 Hz) earthquake located within the edifice. Due to multiple internal reflections off the boundaries of the chamber and the conduit, prolonged reverberations occur, which are guided along the conduit. Temporal and spectral analyses of synthetic seismograms illustrate that the size of the magma chamber and the width of the conduit are critical in determining the magnitude and dominant frequencies of the seismic resonances. Specifically, models with larger magma chambers and wider conduits consistently yield larger resonance amplitudes at distinct frequencies. At greater distances from the conduit, an intensified scattered wavefield with a broad frequency range indicates the presence of a substantial magma chamber within the volcanic edifice. Resonance frequencies reach up to 23 Hz, underscoring significant frequency shifts. In general, these externally initiated resonances may appear as tremor-like signals at seismic stations on the edifice, accompanying more conventional seismic events in its proximity.