Site Effects Assessment in Bishkek (Kyrgyzstan) Using Earthquake and Noise Recording Data

Parolai, Stefano; Orunbaev, S.; Bindi, Dino; Strollo, Angelo; Usupaev, S.; Picozzi, Matteo; Giacomo, Domenico Di; Augliera, P.; D’Alema, Ezio; Milkereit, Claus; Moldobekov, Bolot; Zschau, Jochen

doi:10.1785/0120100044

Cited by 40 publications

(29 citation statements)

References 27 publications

(19 reference statements)

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“…The SMZ zonation of Bishkek ascribes intensities from VIII, in the southern part of town, to intensities larger than IX in the northern part. The variability of local site amplifications in Bishkek has been recently evaluated (Parolai et al 2010) and its effect on seismic risk assessed (Bindi et al, 2011a), showing that site effects can contribute to intensity increments as large as 2 units in the north part of the town. Figure 8 compares the hazard curves estimated in this study for Bishkek with the values provided by Nurmangambetov et al (1999).…”

Section: Assessed Hazard For the Main Townsmentioning

confidence: 99%

Seismic hazard assessment in Central Asia: Outcomes from a site approach

Bindi

Abdrakhmatov

Parolai

et al. 2012

Soil Dynamics and Earthquake Engineering

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In the process of updating existing PSHA maps in Central Asia, a first step is the evaluation of the seismic hazard in terms of macroseismic intensity by applying a data driven method. Following the Site Approach to Seismic Hazard Assessment (SASHA) , the evaluation of the probability of exceedance of any given intensity value over a fixed exposure time, is mainly based on the seismic histories available at different locations without requiring any a-priori assumption about seismic zonation. The effects of earthquakes non included in the seismic history can be accounted by propagating the epicentral information through a Intensity Prediction Equation developed for the analyzed area. In order to comply with existing building codes in the region that use macroseismic intensity instead of PGA, we evaluated the seismic hazard at 2911 localities using a macroseismic catalogue composed by 5322 intensity data points relevant to 75 earthquakes in the magnitude range 4.6-8.3. The results show that for most of the investigated area the intensity having a probability of at least 10% to be exceeded in 50 years is VIII. The intensity rises to IX for some area struck by strong earthquakes in the past, like the Chou-Kemin-Chilik fault zone in northern Tien-Shan, between Kyrgyzstan and Kazakhstan, or in Gissar range between Tajikistan and Uzbekistan. These values are about one degree less than those evaluated in the Global Seismic Hazard Assessment Program (GSHAP;Ulomov, 1999). Moreover, hazard curves have been extracted for the main towns of Central Asia and the results compared with the estimates previously obtained. A good agreement has been found for Bishkek (Kyrgyzstan) and Dushanbe (Tajikistan), while a lower probability of occurrence of I=VIII has been obtained for Tashkent (Uzbekistan) and a larger one for I=IX in Almaty (Kazakhstan).2

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Section: Assessed Hazard For the Main Townsmentioning

confidence: 99%

Seismic hazard assessment in Central Asia: Outcomes from a site approach

Bindi

Abdrakhmatov

Parolai

et al. 2012

Soil Dynamics and Earthquake Engineering

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“…The spectra have been smoothed using a 10% triangular window of the central frequency equal-spaced in logarithmic scale. Logarithmic averages of pre-event noise HVSRs and of earthquake SSRs have been estimated for the sites (Parolai et al 2010). Along with the network of 19 stations, single station seismic noise was also recorded in the urban area covering the whole city at nearly 200 points.…”

Section: Geology Of the Regionmentioning

confidence: 99%

“…The fundamental frequencies are expected to be low, owing to the sedimentary cover thickness in the area. The upper bound of the considered frequency range is selected by acknowledging that at higher frequencies, the HVSR of the earthquake data for the reference site (BI04) is showing site amplification (see Parolai et al 2010). Although this band restriction toward higher frequencies might limit the ability to discriminate the shallow geological structural variations, it will be shown later that the changes in the thin and shallow Quaternary layers can still be successfully captured by using the chosen frequency band.…”

Section: Clustering Analysismentioning

confidence: 99%

“…The grey area shows the frequency range where analyses are not considered because of the spectra ratios being affected by the site response at the reference site (see Parolai et al 2010).…”

Section: Different Dashed Colored Lines Represent Different Clustersmentioning

confidence: 99%

“…Picozzi et al (2009) and Parolai et al (2010), for example, used single station noise measurements to infer resonance frequency maps of Istanbul, Turkey, and Bishkek, Kyrgyzstan, respectively. Parolai et al (2005) and Boxberger et al (2011) used inversions of surface waves from seismic noise array measurements to characterize the shallow geology in cologne (Germany) and Bevagna (Italy), respectively, which in turn can be used to estimate the site response.…”

Section: Introductionmentioning

confidence: 99%

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Improving the spatial resolution of ground motion variability using earthquake and seismic noise data: the example of Bishkek (Kyrgyzstan)

Ullah

Bindi

Pittore

et al. 2012

Bull Earthquake Eng

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Site response analysis plays an important role in seismic hazard and risk assessment, and in defining the optimal engineering design for civil structures. However, due to increasing urbanization, target areas are often too vast to be covered by standard approaches, resulting in large uncertainties in the spatial variability of the expected ground motion. Here, we propose a method to improve the spatial resolution of ground motion variability in terms of Standard Spectral Ratios (SSRs), using earthquakes recorded at a few selected sites for a relatively short amount of time, and seismic noise data collected over a denser grid, taking advantage of clustering and correlation analysis. The method is applied to Bishkek, Kyrgyzstan. Using the K-means clustering algorithm, three clusters of site response types have been identified, based on their similarity of SSRs. The cluster's site responses were adopted for sites where only single station noise measurements were carried out, based on the results of correlation analysis. The spatial variability of the site response correlates well with the main geological features in the area. In particular, variability is noted from south to north, consistent with both the changes in the thickness of the sedimentary cover over the basin and in the Quaternary material outcropping at the surface. This method has therefore the potential to improve the estimation of site effects at the local scale in the future.

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