Low-Frequency Seismic Ground Motion At The Pier Positions Of The Planned Messina Straits Bridge For A Realistic Earthquake Scenario
- Institute of Volcanology and Seismology Petropavlovsk-Kamchatskii (Russian Federation)
- Kamchatka Branch, Geophysical Service Petropavlovsk-Kamchatskii (Russian Federation)
- Department of Earth Sciences, University of Trieste (Italy)
We estimated longer-period (period T>0.5 s) components of the ground motion at the piers of the planned Messina straits bridge. As the shortest fault-to-site distance is only 3-5 km, the kinematic earthquake rupture process has to be described in a realistic way and thus, the causative fault is represented by a dense grid of subfaults. To model the 1908 event, we assume a Mw = 7 earthquake, with a 40x20 km rectangular fault, and pure reverse dip-slip. The horizontal upper side of the rectangle is at 3-km depth, and the N corner of the rectangle is just between the piers. For the fault nucleation point, the least favorable place is assumed and a randomized rupture velocity is used in a particular run. In a typical simulation, the fault motion is initially represented by the time history of slip in each of the subfaults and by the distribution of the final seismic moment among the subsources (forming 'asperities'), both generated as lognormal random functions. The time histories are then filtered in order to fit a chosen source spectral model. The parameters that are conditioning the random functions can be based on the bulk of published fault inversions, or reproduced from an earlier successful attempt to simulate ground motions in the epicentral zone of the 1994, M = 6.7 Northridge, California, earthquake. In the second step of calculations, the Green functions (for each subfault and pier combination) are calculated for a layered halfspace model of the pier foundation stratigraphy, using an advanced Green function calculator, that allows an accurate calculation over the entire relevant frequency band including static terms. Finally, the 3-components of the strong ground motion are obtained at the two piers through convolution and summation over the different subsources. We compare a set of response horizontal velocity spectra (PRV) obtained from our calculations with a reference PRV that is considered as a reasonable upper bound for the possible ground motion near the piers. Our results suggest that the seismic ground motion under Torre Sicilia dominates over this under Torre Calabria and that the median (average log) PRV is generally above the reference one, about 1.1-1.3 times for T>4 s, and up to 2 times for 1<T{<=}4 s. The use of advanced fault and medium models, accounting also for the natural scatter of individual PRV due to events with the same gross source parameters, provides a sound basis for the deterministic engineering estimates of future seismic ground motion.
- OSTI ID:
- 21149001
- Journal Information:
- AIP Conference Proceedings, Vol. 1020, Issue 1; Conference: 2008 seismic engineering conference: Commemorating the 1908 Messina and Reggio Calabria earthquake, Reggio Calabria (Italy), 8-11 Jul 2008; Other Information: DOI: 10.1063/1.2963858; (c) 2008 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-243X
- Country of Publication:
- United States
- Language:
- English
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