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WALDO Broadband VLF

Project status: secondary historical fallback, not a primary acquisition source.

WALDO is a historical archive, not a live receiver. It separates:

  • Broadband VLF: raw receiver samples, normally 100 kHz sampling, suitable for natural-radio features.
  • Broadband LF: normally 1 MHz sampling and much larger files.
  • Narrowband: amplitude and phase of selected transmitters; keep this out of the passive natural-radio input unless explicitly used as a separate modality.

Access

Browsing is available without an account. Downloading requires a free verified account. The site provides daily availability calendars, maps, quick-look plots, and a JavaScript file browser. WALDO also offers larger-scale access by arrangement.

File contract

Broadband files use a MATLAB v4-like format and contain station metadata plus data. The filename encodes station, UTC start time, sampling-rate class, and antenna channel. Broadband VLF is normally int16, with two orthogonal loop antenna channels. The format page documents a Python toolset and the field layout, so a small native reader can avoid loading full files into memory.

Japan relevance

WALDO explicitly lists broadband data from a Japan receiver within 100 km of the 2011 Tohoku earthquake. The data are old, station/date discovery is awkward, and the download workflow is account- and browser-dependent. This makes WALDO useful for a historical case study or optional self-supervised pretraining, but not a good primary source for a current Japan/seismic comparison.

Onboarding rule

Do not add WALDO to the live capture manifest by default. If it is used for a historical experiment, record the station ID, coordinates, UTC coverage, file URL, account/licensing terms, sampling rate, channel orientation, and a nonempty sample checksum. Prefer one short sample and its quick-look plot before requesting bulk data.

Reference: WALDO, data description, and availability page.