Ground motion simulation of the 1908 Messina-Reggio earthquake as a tool for verifying the design earthquake of the Messina Straits Bridge
by
Ezio Faccioli
Department of Structural Engineering, Politecnico, Piazza L. da Vinci 32, 20133 Milano, Italy
Coauthors: Manuela Vanini

Based on the most recent data available (Valensise 2004) for the Messina Straits fault, we simulated, through a hybrid method,the source process,wave propagation,and surface strong ground motions at the support points of the projected one-span suspension bridge across the Messina Straits. The main purpose of the work was twofold, i. e.:

- (a) to realistically evaluate the elastic response spectra at the sites of interest for a violent earthquake such as 1908, including the magnitude of site effects, in order to check the validity of the 1992 design earthquake for the Bridge, and

- (b) to investigate in depth the influence of the directivity of fault rupture on the amplitude and dominant period of surface motions.

We used Hisada's method (wavenumber decomposition) for frequencies up to about 1 Hz, introducing random components in the speed of fault rupture propagation and slip amplitudes across the fault, and physically filtered white noise for frequencies > 1Hz. 20 source processes and as many sets of surface ground motions were thus generated.

The results, in terms of synthetic response spectra at the Sicily and Calabria support sites, show that under conservative assumptions for rupture directivity the design earthquake for the bridge has wide safety margins. These margins are larger at the Calabria than at the Sicily design sites, because of significant differences in site response, arising mainly from the 90 m thick deposits of loose Holocene gravel at the Sicily support site, not present at the corresponding Calabria site, which tend to enhance the spectral amplitudes at oscillation periods between 1 s and 6 s.

Date received: September 13, 2004

Copyright © 2004 by the author(s). The author(s) of this document and the organizers of the conference have granted their consent to include this abstract in Atlas Conferences Inc. Document # caon-51.