The July 22, 2020, Alaska Peninsula, AK tsunami was generated by a Mw 7.8 earthquake (55.068°N 158.554°W), at 2020-07-22 06:12:44 UTC (according to the USGS). The earthquake generated a relatively small tsunami that arrived approximately 20 minutes later at the closest DART 46403, located approximately 295 km away from the epicenter. The proximity of DART 46403 to the epicenter resulted in the tsunami signal being contaminated by seismic noise and unusable for tsunami inversion. While DART 46403 has DART 4G capabilities, meaning it should have been able to filter the tsunami signal from the seismic noise, those capabilities were not activated at the time of the event. The next available DART buoy to detect the tsunami was DART 46402, showing a maximum wave amplitude in deep water just over 0.5 cm approximately 45 minutes after the earthquake. A DART inversion was performed with data from this buoy. Model results shown below were created with the NOAA forecast method using the MOST model via automatic 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 July 22, 2020 Alaska Peninsula tsunami inverted from tsunameter/DARTs data and from USGS finite-fault solution is compared in the graphics with recorded data. Tsunami propagation solutions from DART gauges was computed on the fly while the tsunami was still progressing whereas the finite fault solution was generated after the event. The presented DART-inverted solution was obtained as a linear combination of the sources that best fits the tsunami records from 3 DARTs, 46402, 46408, and 46409.

• DART® comparisons with model data
  • DART 46403, DART 46402, DART 46409, DART 46414, DART 46408
• Source Inversion: 0.479*ac27y+0.666*ac28z+0.743*ac29y+0.189*ac29z

It is noted that all above model results are preliminary. The tsunami source is estimated from inversion of observed waveforms at DARTs using limited number of unit sources. The discrepancies between model results and observations are primarily due to the inability to use DART 46403 for inversion as data from that system would have contained the largest wave amplitudes.