Land subsidence in Venice and Porto Corsini



This paper is a contribution to t h e study of the problem
of subsidence in the Po delta and in t h e Venetian lagoon. We have compared
t h e d a t a supplied by tide gauges in Trieste, Venice and Porto Corsini (Fig. 1)
during t h e period 1896-1966, and in Genoa in t h e period 1894-1966. Although
d a t a were recorded in slightly different periods, these periods are sufficiently
overlapping to allow for a significant statistical comparison. We note t h a t the
movement of t h e annual mean sea level in Genoa and Trieste is greatly different
f r om t h a t of Porto Corsini and Venice and, in order to separate the component
due to eustatic effect f r om any possible movement of the coast, we calculate
t h e polynomial coefficients, t h a t best fit t h e real movements. Approximating
polinomials are of first degree for Genoa and Trieste and of second
degree for Porto Corsini and Venice. We have evaluate the coefficients of
crosscorrelation firstly on original d a t a and then subtracting f r om original d a ta
the best fit polinomials. The correlation is very significant and the trend is
similar in Trieste and Genoa. The power spectrum analysis with the direct
Fourier's method show long periods wich are shared by tide gauges. We
conclude estimating 1,35 mm/year the increase of the mean sea level for t he
eustatic effect in the Mediterranean 3,9 mm/year the subsidence in Porto
Corsini and 1,4 mm/year the subsidence in Venice.

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Published by INGV, Istituto Nazionale di Geofisica e Vulcanologia - ISSN: 2037-416X