Provide an Example of Damage to Buildings or Engineering Works

A tsunami is like a shallow water wave, but in the whole water column, with gravity as the restoring force, not pressure.I feels the water depth, even in water several kilometres deep where it can move up to 900 km/hr yet be only a few centimetres high.The waves speed and wavelength decrease or increase as it reaches shallow water?

One way we know that tsunamis are "gravity" waves and not "pressure" waves, is they are limited by the speed of sound.The speed of sound in ordinary ocean water is 1.5 km/sec.What is the wave speed of a tsunami in km/sec if it can move 900 km/hr in the open ocean? What mach number is this (how many times the speed of sound in water)?