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

Sudhaus, Henriette; Ritter, Joachim

doi:10.1007/s10950-008-9140-0

Cited by 3 publications

(3 citation statements)

References 24 publications

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“…The noise amplitudes increase from the southern part of the metropolitan area towards the North. The same effect of ground motion amplification was observed by an amplitude and site effect study utilizing earthquake signals and related to resonance effects in the unconsolidated sediments above the dipping Neogene‐Cretaceous boundary (Mandrescu et al 2004; Sudhaus & Ritter 2009). Our similar observation for the noise amplitudes demonstrates the potential of noise amplitude mapping to complement information for site effect studies.…”

Section: Discussionsupporting

confidence: 60%

“…Regarding the noise amplitudes a trend of decreasing noise amplitudes from the North towards the South is observed at day‐ and nighttime and all analysed days in the frequency ranges between 0.09 and 0.25 Hz. An amplitude and site effect study by Sudhaus & Ritter (2009), using waveforms of the URS data set, found the same effect of latitude‐dependent ground motion amplification across the Bucharest area. Sudhaus & Ritter (2009) relate this effect to resonance effects in the unconsolidated sediments above the distinct dipping Neogene–Cretaceous boundary from 800 m depth in the south to 2000 m depth in the north (Mandrescu et al 2004; Sèbe et al 2009).…”

Section: Resultsmentioning

confidence: 87%

“…An amplitude and site effect study by Sudhaus & Ritter (2009), using waveforms of the URS data set, found the same effect of latitude‐dependent ground motion amplification across the Bucharest area. Sudhaus & Ritter (2009) relate this effect to resonance effects in the unconsolidated sediments above the distinct dipping Neogene–Cretaceous boundary from 800 m depth in the south to 2000 m depth in the north (Mandrescu et al 2004; Sèbe et al 2009). Also for the URS data set Ziehm (2006) applied a comprehensive H/V analysis for the Bucharest area.…”

Section: Resultsmentioning

confidence: 87%

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Time domain classification and quantification of seismic noise in an urban environment

Groos¹,

Ritter²

2009

Geophysical Journal International

141

108

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S U M M A R YBroad-band urban seismic noise (USN) must be considered as a temporally and spatially non-stationary random process. Due to the high variability of USN a single measure like the standard deviation of a seismic noise time-series or the power spectral density at a given frequency is not enough to characterize a sample (time-series) of USN comprehensively. Therefore, we use long-term spectrograms and propose an automated statistical classification in the time domain to quantify and characterize USN. Long-term spectrograms of up to 28 d duration are calculated from a broad-band seismic data set recorded in the metropolitan area of Bucharest, Romania, to identify the frequency-dependent behaviour of the timevariable processes contributing to USN. Based on the spectral analysis eight frequency ranges between 8 mHz and 45 Hz are selected for our proposed time domain classification. The classification scheme identifies deviations from the Gaussian distribution of 4-hr-long timeseries of USN. Our classification is capable to identify Gaussian distributed seismic noise timeseries as well as time-series dominated by transient or periodic signals using six noise classes. Four additional noise classes are introduced to identify corrupt time-series. The performance of the method is tested with a synthetic data set. We also apply the statistical classification for the data set from Bucharest in three time windows (0-4, 8-12 and 13-17 EET) at 11 d in the eight frequency ranges. Only 40 per cent of the analysed time-series are observed to be Gaussian distributed. Most common deviations from the Gaussian distribution (∼47 per cent) are due to the influence of large-amplitude transient signals. In all frequency ranges between 0.04 and 45 Hz significant variations of the statistical properties of USN are observed with daytime, indicating the broad-band human influence on USN. We observe the human activity as a dominant influence on the USN above and below the frequency band of ocean-generated microseism between 0.04 and 0.6 Hz. Our time domain classification and quantification is furthermore capable to resolve the influence of wind on seismic noise and a known site effect variation in the metropolitan area of Bucharest. The information about noise amplitudes and statistical properties derived automatically from broad-band seismic data can be used to select time windows containing adequate data for seismic noise utilization like H/V-studies or ambient noise tomography.

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Section: Discussionsupporting

confidence: 60%