Seismic Signature of Rain and Wind Inferred From Seismic Data

Rindraharisaona, E. J. ; Réchou, Anne ; Fontaine, F. R. ; Barruol, G. ; Stamenoff, P. ; Boudevillain, B. ; Rigaud-Louise, François ; Delcher, E.

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<p align=justify>Seismic stations are increasingly used to monitor river activity and to quantify sediment transport during flood events. In tropical regions, cyclone-induced floods are often associated with heavy rain and strong wind episodes, generating complex seismic records involving the simultaneous signature of water, sediment, rainfall and wind. Hence, seismic characterization of rain and wind is then required to better decipher each process and improve our understanding of the river seismic signature. In this study, we investigate experimentally the seismic response of rain and wind using data recorded by geophones deployed in various soil types and at different burial depth (BD), co-located with various meteorological instruments. Our results show that the power spectral density (PSD) of the seismic noise intensifies at a frequency between 60 and 500 Hz for rain and 5 and 500 Hz for wind, in the presence of rain precipitation as low as 0.025 mm/min and/or wind speed ≥3 m/s. PSD analysis indicates that the seismic signal associated with rain decreases with the BD with a value of ∼2-5 dB in a depth difference of 10 cm. We also observe that each soil type has its own seismic signature. The 4-min root mean square correlation between the seismic signal amplitude and the rain precipitation suggests that they best correlate with Pearson coefficient >0.90 at BD of 30 cm. The transfer function between the precipitation rate (or kinetic energy) and the seismic signal amplitude shows that the signal recorded by the geophone can be used as a robust proxy for these parameters.</p>
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