%0 Journal Article
%T Analytical Solution for the Pressure Oscillations Caused by Trains of Solitary Waves within Confined Coastal Aquifers
%A Marilena Pannone
%J ISRN Civil Engineering
%D 2012
%R 10.5402/2012/953204
%X An exact analytical solution is proposed for the pressure oscillations within deep coastal aquifers under the action of tidal level time-variations attributable to train of solitary waves originating off-shore. The purpose of the study is to relate the characteristics of the response of the system to amplitude, steepness, and asymmetry of the soliciting waves, in order to assess its vulnerability to events like violent seaquakes and consequent tsunamis. The time needed by the forcing perturbations, approximated by consecutive triangular impulses, to attain their maximum is assumed to be always smaller than the aquifer diffusive time, in order to evaluate the consequences of the sudden raise of water level along the shoreline, typical of those quite extreme phenomena. 1. Introduction Common waves propagating on the sea surface are a direct consequence of the wind. When it starts to blow, any even weak irregularity in the flow pattern will produce corresponding local variations of the atmospheric pressure on the water table, triggering off the formation of series of ripples amplified and pushed away by the wind itself. That phenomenon of gradual growth and associated coalescence can lead, off-shore and under the action of particularly intense fluxes, to waves of considerable height, which in extreme cases can measure up to 8 meters in the Mediterranean sea and over 15 meters in the oceans. Due to their very slow attenuation, mainly attributable to the effect of the friction, those sea waves keep on propagating when the forcing mechanism stops, reaching zones that can be even very far from the origin. Totally different is the genesis of the solitary waves, also known as ¡°tsunami¡± (a Japanese term meaning ¡°port wave¡±), which are induced by impulsive phenomena like submarine earthquakes (e.g., [1, 2], see also Figure 1) or the fall in the sea of big rock and ice masses. Figure 1: Example of earth-tsunami genesis. The tsunami waves travel on the sea surface according to peculiar laws, with almost no decay, over distances of thousands of kilometres. Their rate of propagation (Lagrange velocity) is given by where indicates the local sea depth and is the specific gravity. For instance, a sea depth of 5£¿km would correspond to a tsunami velocity of about 800£¿km/h (comparable to the regime speed of an aircraft). Characterized by a limited amplitude when they propagate in open sea (about 1£¿m), tsunamis¡¯ waves become gigantic water walls (10¨C30£¿m) while breaking on the coast, with predictable ruinous effects, which sometimes can be even catastrophic. Two eloquent
%U http://www.hindawi.com/journals/isrn.civil.engineering/2012/953204/