The March 4, 2021, Kermadec Islands tsunami was generated by a Mw 8.1 earthquake (29.735°S 177.282°W), at 2021-03-04 19:28:32 UTC (according to the USGS). 45 minutes later, the tsunami was recorded offshore at newly deployed DART 4G 5401001, located approximately 703.2 km away from the epicenter. For the first time, a DART inversion was performed with the data from a New-Zealand-owned DART buoy with 4G capabilities. The largest coastal tsunami amplitude was ~70 cm and was detected at the Kingston, Norfolk Island (Australia) tide station 3 hour 15 minutes after the earthquake. Model results shown below were created with the NOAA forecast method using the MOST model via inversion of the source with NOAA's TFS (Tsunami Forecast System).

The graphics display preliminary modeling analysis, showing qualitative and quantitative information about the tsunami, including tsunami wave interaction with ocean floor bathymetric features, and neighboring coastlines. Tsunami model amplitude information is shown color-coded according to the scale bar.

Modeling Results

Model amplitudes calculated with the MOST forecast model. Click to see large image.

Propagation animation Click for animation.

• Model amplitudes are calculated with the MOST forecast model. Filled colors show maximum computed tsunami amplitude in cm during 24 hours of wave propagation.
  • Maximum wave amplitude
    
• Propagation animation on YouTube

Preliminary Model

Comparison of the March 4, 2021 Kermadec Islands tsunami recorded at tsunameter/DARTs and tide gauges (black) with model results computed using the DART-inverted source (red) solution is presented in the graphics. The DART model time series are obtained from the pre-computed generation/propagation forecast database in real time, after automatically fitting models to tsunami records from the DARTs.

• DART® comparisons with model data
  • Composite plot: DARTs 5401001, 5401000, 5501002, 51425, 52406, 51407
• Coastal sea-level gauge comparisons with model data
  • Composite plot farfield
  • Composite plot nearfield
• Source Inversion: 0.13*nt18a+3.67*nt19a

It is noted that all above model results are preliminary. The tsunami source is estimated from inversion of observed waveforms at DARTs using a limited number of unit sources. The discrepancies between model results and tide gauge observations are mostly due to 1) the limited knowledge of the earthquake/tsunami source configuration at this point, and 2) the data quality and the low resolution of the bathymetry for locations where no forecast models are available in the NOAA TFS: Kingston Norfolk, North Cape, Tauganra, East Cape, Great Barrier Island, Gisborne, Wellington, Chatham Island, Mare Island, La Libertad, which were created on-the-fly using the low-resolution global relief DEM combined with the SRTM 90-m topography.