The Resonance of the Surface Waves. The H/V Ratio in the Metropolitan Area of Bucharest
- National Institute for Earth Physics, Calugareni 12, PO Box MG2, Bucharest-Magurele (Romania)
The purpose of this work is to evaluate the natural period of oscillation T{sub 0} for soils in Bucharest city area. We will start by examine the elastic waves excited at the surface of an isotropic body by an oscillatory, localized force (Rayleigh waves). We define the 'H/V'-ratio as the ratio of the intensity of the in-plane waves (horizontal waves) to the intensity of the perpendicular-to-the-plane waves (vertical waves). It is shown that this ratio exhibits a resonance at a frequency which is close to the frequency of the transverse waves. It may serve to determine Poison's ratio of the body. We consider the ratio H/V of the horizontal to the vertical component of the Fourier spectrum for the seismic events recorded at 34 locations during the period October 2003 to August 2004. The method gives reliable data regarding the fundamental frequencies for soil deposits and the results of this experiment allows us to improve the known distribution of T{sub 0}--regularly calculated with the approximate formula T = 4h/v{sub s}. The earthquakes with M{sub w}>4 that occurred on 21.01.2004, 07.02.2004, 17.03.2004 and 04.04.2004 will be used as input to compute H/V ratios for each site of a URS stations in the area of Bucharest city. The H/V ratio is also calculated from noise recordings in the same areas. Computation of H/V spectral ratios are performed by means of the SeismicHandler and J-SESAME software showing the reliability of the method used for the sites located in Bucharest. The fundamental period obtained for the majority of sites is in accordance with already known results. By obtaining the fundamental period for much more and different spots situated in the Bucharest area we covered the zones where these data did not exist before. This study is significant in seismic risk mitigation for the Bucharest city area, for a safer seismic design and for the improvement of microzonation efforts.
- OSTI ID:
- 21148980
- 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: 10.1063/1.2963837; (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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