The ocean sensors in NOAA’s archive of the 2011 Tohoku tsunami

The first reported reading came from an offshore station

The NOAA event summary says station 21418 first recorded the tsunami about 25 minutes after the earthquake. The event archive places that station at latitude 38.718 north and longitude 148.698 east, with a listed depth of 5,500 metres. NOAA’s near-field plot also includes station 21413. Source 2 Source 1

Depth describes where the sensor was deployed

The archive’s station depth is given in metres. It reports the water depth at the station rather than the size of the passing tsunami. NOAA’s data files contain observations and a fitted tidal component. The map tooltips display station depth. Source 1

The event archive reaches beyond the map’s frame

The map shows seven northwestern Pacific positions. The data table retains all 35 archive station rows, including stations across the central and eastern Pacific. The archive table identifies stations with records for the event and does not itself give a comparable wave-height ranking. Source 1 Source 2

NOAA compared observations with a forecast model

NOAA says its event forecasts used its MOST model and a tsunami source inferred from two DART records. The agency separately published comparisons with ocean instruments and coastal sea-level gauges. The station map here plots the archival coordinates. Source 2 Source 1

Sources

• NOAA National Centers for Environmental Information Tohoku DART station archive
• NOAA Center for Tsunami Research 11 March 2011 event summary