Urban shakemap methodology for Bucharest

Abstract

[1] We develop a methodology for a shakemap for the Romanian capital Bucharest that can be rapidly computed and delivered to the public, once real-time data access is available to a sufficient extent. The methodology, with which the Californian shakemaps are generated, cannot be transferred to Bucharest, due to a missing understanding of the relationship between the geological near-surface structure and the ground motion amplification. However, a systematic incorporation of previous seismological observations using Fourier Amplitude Spectra of weak and strong ground motion and a recent urban broadband experiment in Bucharest allows us to interpolate computed seismic intensities from 11 sites, where accelerometers measure the actual motion of a specific earthquake to 31 additional locations in the city, so that a reasonably reliable distribution of ground motion in the city can be determined. We demonstrate this methodology using the M W = 6.0 intermediate-depth earthquake

The shear wave velocity underneath Bucharest city, Romania, from the analysis of Love waves

“…Such scenarios are used to reliably adjust building codes and city planning. Currently such estimations are done for Bucharest by extrapolating actual measurements of past seismic motions (Bartlakowski et al 2006), or by modelling the seismic ground motion from the known underground structure and expected source characteristics (Miksat 2006), or even a combination of both. Consequently, the precise knowledge of the underground structure is an essential component of seismic hazard assessment, especially in the presence of a soft sedimentary cover that can generate severe site effects with amplification of wave amplitudes (Lungu et al 1999).…”

Broadband frequency-dependent amplification of seismic waves across Bucharest, Romania

“…Recent strong motion studies, conducted to determine the peak ground acceleration (PGA) for risk assessment, revealed a strong spatial and frequency-dependent variability of PGA across the city (e.g. Wirth et al 2003;Aldea et al 2004;Cioflan et al 2004;Bartlakowski et al 2006) as well as a dependence on the absolute seismic amplitude (Mândrescu et al 2004).…”