Development of geotechnical microzonation model for Yenisehir (Bursa, Turkey) located at a seismically active region

Abstract

Earthquake hazard zonation for urban areas, mostly referred to as seismic microzonation, is the first and important step towards a seismic risk analysis and mitigation strategy in populated regions. Proper understanding of the local subsurface ground conditions is essential for a realistic assessment. Turkey is one of the earthquake prone countries in the World and the lessons particularly drawn from the devastating 17 August 1999 and 12 November 1999 earthquakes of Turkey revealed the importance of microzonation studies. The purpose of this study is to further develop a geotechnical microzonation model regarding the suitability of the residential areas in Yenisehir (Bursa), a rapidly developing settlement area in a seismically active region of Turkey. For this purpose, properties and dynamic behavior of the Quaternary alluvial soils in study area were assessed. Soil classification, soil amplification, natural soil predominant period, resonance phenomena and liquefaction potential of the study area were evaluated using borehole data and microtremor measurements. The raw data obtained from previous studies carried out at Yenisehir were used for these assessments. Geotechnical microzonation map of Yenisehir was produced according to the surface damage due to liquefaction, soil amplification and distance to streams maps; by using Geographical Information Systems (GIS) based Multi-Criteria Decision Analysis. The weight values were assigned to the layers using Analytical Hierarchical Process method by pairwise comparisons. The produced geotechnical microzonation map indicated that the most critical areas are located in the densely populated middle and the southeastern parts of the study area.