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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-22 1:37 |
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Conference: Bucharest University Faculty of Physics 2007 Meeting
Section: Atmosphere and Earth Science; Environment Protection
Title:
Estimation of Site Effects in the Eastern Part of Romania on the Basis of H/V Ratios of S and Coda Waves Generated by Vrancea Intermediate-depth earthquakes
Authors:
Bogdan Grecu, Victor Raileanu, Andrei Bala, Dragos Tataru
Affiliation:
National Institute for Earth Physics
E-mail
bgrecu@infp.ro
Keywords:
site effects, resonant frequencies, S and Coda waves
Abstract:
Romania has been repeatedly struck by large Vrancea intermediate-depth earthquakes. The studies of the August 30, 1986 (Mw = 7.2) and May 30, 1990 (Mw = 6.9) earthquakes have shown the important role played by the local and regional conditions in the distribution of the effects of the Vrancea events (Mandrescu, 1995). From May to November 1999, 120 temporary stations were deployed within CALIXTO tomography experiment to collect earthquakes data for 3-D image determination of the lithosphere structure at the SE Carpathian Arc region. The local soil conditions at the considered sites vary from metamorphic rock to thick and water-saturated sedimentary formation. A number of 56 local earthquakes with magnitude between 3.0 and 4.2 were recorded by the CALIXTO stations. This data set yields well documented experimental evidence for weak to moderate local amplifications in the study area. In the present paper we concentrate on evaluating site effects at stations situated in the Eastern part of Romania by applying the H/V ratio to two sets of data: S and coda waves generated by intermediate-depth earthquakes. The results show that the method is able to identify the resonant frequencies of the sites no matter what data is used. The shapes of the spectral ratios obtained from S-waves and coda waves are generally in good agreement. In addition, the analysis of coda waves shows resonant peaks at low frequencies that are not well identified when using S-waves data. The results of our study provide a basis for site-dependent hazard analysis in terms of engineering ground motion parameters for the territory of Romania.
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