THE PRODUCTION OF ESTIMATED-VS30 MAPS FOR TURKIYE ON GIS BY USING THE GEOLOGICAL AND ELEVATION MAPS
World Conference on Earthquake Engineering proceedings, International Association for Earthquake Engineering, 2024
- Yayın Türü: Kitapta Bölüm / Araştırma Kitabı
- Basım Tarihi: 2024
- Yayınevi: International Association for Earthquake Engineering
- Orta Doğu Teknik Üniversitesi Adresli: Evet
Özet
Vs30, the average S-wave velocity for top 30 m of ground is used for prediction of site effects on scenario-or event-based seismic intensity maps (Shakemaps), since this parameter is generally used for estimation of site amplification factors in ground-motion prediction equations, and consequently in construction of site-specific design spectra in several seismic codes involving that of Turkey. Therefore, the national 1:500,000-scale digital geological map, and 30 m/ 90 m resolution digital elevation data sets are used for development of estimated-Vs30 map of the county. The uniform database for Vs30 determined through MASW surveys on sites of the strong-motion stations which are operated by the Disaster and Emergency Management Presidency of Turkey (AFAD) was used for statistical conclusions. First the geological units are classified according to the formation descriptions, map details, and the statistical properties of Vs30 distributions. It was concluded that 4 geological classes related to the geological ages can be considered in estimation of Vs30. Second, the most significant topographical functions to estimate Vs30 was investigated through the correlation analyses. Consequently, the topographical slope, convexity and texture were observed to contribute significantly to Vs30 estimations. The optimum grid distance on digital elevation map for calculation of these topographical functions was estimated by statistical sensitivity analyses. Finally, the coefficients of empirical functions that are relating these topographical parameters to Vs30 were determined for 4 classes separately by using the ordinary principle of least-squares. Alternatively, the quantile regression analyses were used for drawing envelopes of Vs30 pertinent to a given probability of exceedance, including the probability of 16% being lower, since this corresponds to mean minus one sigma for a Gaussian distribution presumed in practical applications. Finally, Vs30 maps of Turkey for mean and lower estimations of Vs30 were produced on GIS. A final discussion on Vs30 estimations for the region severely affected by the recent Mw7.8 and Mw7.5 February 6th, 2023 Earthquakes in Turkey is presented.