Not an official forecast
Miyako, Japan Tsunami, April 20, 2026
Main Event Page
The April 20, 2026, Miyako, Japan tsunami was generated by a Mw 7.4 earthquake (39.953°N 143.046°E), at 2026-04-20 07:53:00 UTC (according to the USGS). The Japan Meteorological Agency (JMA) issued a tsunami warning and advisory, reporting the earthquake magnitude as Mw 7.7. The resulting tsunami was first detected by the Miyako tide gauge (~100 km WSW from the earthquake epicenter) approximately 17 minutes after the earthquake. A maximum wave peak of 80 cm was observed at Kujiko tide gauge 41 minutes after the earthquake. Maximum tsunami amplitudes measured at other tide stations along Honshu's coastlines ranged between 10 and 40 cm.
A weak tsunami signal (< 0.8 cm) was detected in deep water at DART 21419, located approximately 1,150 km northeast of the epicenter, about 1 hour 20 minutes after the earthquake. A DART inversion was performed with data from this DART. Model results shown below were created with the NOAA forecast method using the MOST model via inversion of the source.
Global Tsunami Propagation Forecast
The Miyako tsunami propagation forecast model, shown in the figure above, was created using the NOAA forecast method. This method combines pre-computed "unit source" solutions to fit DART observations. The tsunami source of the Miyako tsunami is estimated from inversion of observed waveforms at only one DART 21419. The filled colors on the figure indicate the maximum computed tsunami amplitude in meters over 24 hours of wave propagation. Additionally, the dynamics of the tsunami's propagation across the Pacific are visualized in the animation below.
Coastal Forecast Model Results
Coastal tsunami forecasts were generated using a two-tiered modeling approach. The initial basin-wide tsunami propagation model provided input for higher-resolution coastal forecasts.
For Japan's coastline, three site-specific models were developed on the fly during the event using Digital Elevation Models (DEMs). These simulations used a grid resolution of 3 arc sec (approximately 90m) around the sea-level gauge locations to model tsunami amplitudes.
In contrast, the models for Hawaiian locations were pre-existing, developed for SIFT operations, and featured a higher grid resolution.
Comparison of the April 20, 2026 Miyako, Japan tsunami recorded at tsunameter/DARTs and tide gauges with model results computed using the DART-inverted source (red) is presented in the graphics bellow. The DART model time series are obtained from the pre-computed generation/propagation forecast database, after automatically fitting models to tsunami records from DART 21419.
- DART® comparisons with model data
- Coastal Tide Gauge Comparisons with Model Data
- Source inversion: 0.41*ki25a + 0.17*ki25z
It is noted that all above model results are preliminary. The tsunami source is estimated from inversion of observed waveforms at only one DART using a limited number of unit sources. The discrepancies between model results and tide gauge observation are mostly due to relatively low-quality and low-resolution DEMs in shallow water regions.
Disclaimer: The models on these pages show the results of ongoing research to enhance tsunami science and to improve NOAA operational tsunami forecasts. These products were developed during or shortly after the tsunami event, are intended for research use, and are not an official forecast. They should not be used as the basis of any public or private policy decisions. Please contact NCTR to find if there are more detailed follow-on analysis results.
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When using information from this page, please credit NOAA / PMEL / Center for Tsunami Research
