The whole library leads to one idea. Infrasound is not just a beautiful natural phenomenon. It is a signal that often arrives ahead of disaster, and that can be caught. Therein lies the meaning of the HERD project.
A few minutes decide everything
In a tsunami, eruption, avalanche or meteor explosion, the destructive part arrives with a delay. But infrasound in the air travels at the speed of sound and barely attenuates — so it often outruns the threat itself. Those minutes are the time to move away from the water, stop the train, lead people off the slope.
This has already been proven on large events
- The 2004 tsunami. Infrasound from the Sumatra earthquake and tsunami was recorded by stations thousands of kilometres away — the signal carried information about the event.12
- Geophysical threats. Infrasound is being considered as an indicator for tsunami and other hazard warning systems.3
- Volcanoes and meteors. The global network instantly "hears" large eruptions and bolides.4
- Avalanches. Already-operating arrays give a real-time signal.5
- Tonga 2022. The eruption generated an atmospheric Lamb wave that drove tsunamis across the planet 2+ hours earlier than the usual arrival time — a new mechanism visible directly in the pressure data.6
- The ionosphere. After Tonga 2022 a new operational channel emerged: ionospheric signatures of the tsunami and the Lamb wave, measured by GNSS-TEC (Ravanelli et al., 2023).7
The early-warning toolbox is widening from other directions too: networks of ordinary Android phones (Allen et al., 2025) and infrasound detection of lahars (Johnson et al., 2023) add new, cheap sources of signal.
Big science has proven the principle. Our task is to make it available to every coastline.
Where HERD comes in
Expensive stations are rare and far apart. HERD is building a dense network of cheap sensors and open processing, so that early warning stops being a privilege of wealthy states. First — to prove honestly that a cheap network catches events and does not confuse them with weather. Then — scale.
For an ordinary tectonic tsunami, seismic waves and DART buoys work fastest — HERD complements them: it provides an independent infrasound channel, multi-node confirmation, and a "last-mile" local alert. HERD's real unique lead time is in atmospherically-coupled and volcanic events (Hunga-Tonga type): the network catches their pressure wave hours ahead, while seismic systems miss it. We are honest: right at the coast the lead is minutes, and we do not promise to "hear the tsunami before it arrives" on cheap hardware.
- In the open ocean a tsunami races at the speed of a jet airliner (~700–800 km/h) — but infrasound in the air is still faster.
- After 2004, the CTBTO was required to pass its data directly to national tsunami warning centres.
- Near the shore a tsunami slows and grows sharply in height — so a head start of a few minutes is enough to move inland.
Listen to the planet together
This is a living research project, born of a love for elephants and the idea of warning of disaster. Join us.
Join The whole librarySources for this article
These sources are part of the full HERD library — 272 vetted sources, with meaning search and topic filters.
- peer-reviewed Le Pichon A. et al. (2005). Infrasound associated with 2004–2005 Sumatra earthquakes and tsunami. GRL 32. agupubs.wiley.com
- review Garcés M. et al. (2005). Infrasound from the 2004 Sumatra earthquake and tsunami. ASA. acoustics.org
- peer-reviewed Bittner M. et al. (2010). Mesopause perturbations as a potential tsunami indicator. NHESS 10. nhess.copernicus.org
- peer-reviewed Matoza R.S. et al. (2022). Global seismoacoustic observations of the January 2022 Hunga eruption, Tonga. Science 377. science.org
- peer-reviewed Marchetti E. et al. (2015). Infrasound array detection of snow avalanches. NHESS 15. nhess.copernicus.org
- peer-reviewed Kubota T., Saito T., Nishida K. (2022). Global fast-traveling tsunamis driven by atmospheric Lamb waves on the 2022 Tonga eruption. Science 377(6601). doi.org
- peer-reviewed Ravanelli M. et al. (2023). Tsunami and Lamb wave ionospheric signatures from the 2022 Hunga Tonga eruption (GNSS-TEC). Pure Appl. Geophys. 180. doi.org
- history Ripepe M., Marchetti E. (2002). Array tracking of infrasonic sources at Stromboli volcano. Geophysical Research Letters 29(22), 2076. doi.org
- peer-reviewed Occhipinti G., Rolland L., Lognonné P., Watada S. (2013). From Sumatra 2004 to Tohoku-Oki 2011: the systematic GPS detection of the ionospheric signature induced by tsunamigenic earthquakes. Journal of Geophysical Research: Space Physics 118(6), 3626-3636. doi.org
- review Bernard E., Titov V. (2015). Evolution of tsunami warning systems and products. Philosophical Transactions of the Royal Society A 373(2053), 20140371. doi.org
- organization NOAA Pacific Marine Environmental Laboratory / NOAA Center for Tsunami Research. DART (Deep-ocean Assessment and Reporting of Tsunamis) real-time tsunami monitoring network. nctr.pmel.noaa.gov
- organization NOAA National Weather Service (Pacific Tsunami Warning Center & National Tsunami Warning Center). U.S. Tsunami Warning Centers (Tsunami.gov). tsunami.gov
HERD (2026). Early warning: what it's all for. HERD — Infrasound library. https://theherd.network/infrasound/en/early-warning