A uniform approach to seismic site effect analysis in Bucharest, Romania
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文摘
As a uniform approach to the assessment of ground motion variation within the Romanian capital Bucharest we analyze and compare strong motion records from analog recorders, weak motion data from a modern digital accelerometer network, and intensity observations of previous strong earthquakes. These different data sets allow to clearly characterize geographical trends in the distribution of ground shaking in the city for future earthquakes. Below 2 Hz the variability is small. Between 2 and 5 Hz, however, variations by a factor of 3–4 have to be expected. As the key source for the seismic hazard—the intermediate depth Vrancea earthquakes—remain at hypocentral distances in excess of 150 km from the city the ground motion variation must be predominantly attributed to site effects. This geometry of Vrancea sources to the site of Bucharest is ideal for the application of source-site separation techniques. However, despite this fact site effect amplification functions display a very large amount of aleatory uncertainty. In other words the standard source-site parameterization is too simple and we do not yet fully understand the cause and size of site effects.