Obviously some people could have been killed by collapsing buildings then washed away so we’ll never know.
But has anyone seen figures estimating how many died/would have died absent the tsunami?
About a month after the earthquake, Tokyo Metropolitan Police conducted an investigation to determine the cause of death of victims. They examined close to 16,000 corpses and found that 92.5% of them drowned. 4.4% died of trauma, 1.1% of burns. In 2% of cases, the cause could not be determined. Extrapolating with today’s numbers of dead and missing, we get about 17,500 deaths by drowning, 838 deaths by trauma and 209 deaths by fire.
Note, however, that deaths by trauma were not all caused by the earthquake itself as many people were killed or injured by debris from the tsunami. The actual death toll strictly from the quake itself is probably quite low. For instance, no one died in the city of Kurihara (pop. 73,000) despite tremors of intensity 7 on the Japanese scale.
Sources: