I asked Gemini about the Great East Japan Earthquake and tsunami.
Tsunami that occurred during the Great East Japan Earthquake (March 11, 2011)
maximum height
As you said
It was much higher than 30m.
Although there are some differences depending on the results of the survey, the officially recorded maximum heights (highest height above sea level reached when the tsunami reached the coast) are as follows:
Maximum Height:
A tsunami wave observed in the Iwate Prefecture, Japan.
40.5m
The final results of the investigation were presented.