The run-up of long, strongly nonlinear waves impinging on a vertical barrier can result in remarkable amplification of the far-field amplitude of incoming waves [1,2]. Such an extreme run-up is the result of an evolution process in which long waves experience strong amplification under the action of nonlinear steepening followed by the formation of undular bores, consisting of nonlinearly dispersive wave trains.
Rather than addressing the genesis of such extreme run-ups in any detail, this article describes a specific aspect of the problem; the associated pressure fluctuations at the wall. Numerical computations of the near-wall pressure field show that non-hydrostatic effects can strongly affect the dynamic loads exerted on the wall, and consequently, the high-frequency component of the pressure loads results is significantly enhanced with respect to that of the wave spectrum itself. This observation suggests that also long oceanic waves, at least in some conditions, can be a source of seismic noise.