A tsunami is not just one wave, but a series of waves.

VOA: special.2009.03.17

Residents compared the wave of water that hit them to a tsunami.

VOA: standard.2009.03.27

Japanese meteorological authorities said a small tsunami wave of two feet could result from the earthquake.

FORBES: News Wrap: Japan Lifts Tsunami Warning Following 6.7 Quake

Conversely, a tsunami wave rolling up the channel would grow in height as it became increasingly constricted.

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That quake generated a 33-foot (10-meter) tsunami wave, and some scientists believe the quake may have triggered the eruption of Mount Fuji 49 days later, Morris said.

CNN: Widespread destruction from Japan earthquake, tsunamis