A geophysical study on soil conditions in flood-affected Selimpasa area, Istanbul, Turkey

Abstract

Multi-channel analysis of surface waves (MASVV) and micrometer array measurements (MAM) have been carried out in the flood-prone areas of Selimpasa, Kavakli, Ortakoy and Kadikoy in Turkey to understand several soil problems, especially soil amplification during earthquakes. In the region, there are now more than 80 geotechnical boreholes with SPT and laboratory test data, as also MASW-MAM geophysical measurements at more than 100 locations. All these data have been evaluated to classify the soils according to Eurocode 8, determine soil amplification and finally to obtain a microzonation map. According to the Eurocode soil classification system, there are D, B and C type soils in the area of study. In the final microzonation map, the study area is divided into three sub-regions based on shear wave (Vs) velocities sub-region A (Vs velocities higher than 420 m/s), sub-region B (Vs velocities between 360 and 420 m/s) and sub-region C (Vs velocities lower than 360 m/s). Results show that there are clear relationships between Vs 30 and flood damage effect. Vs 30: 180 m/s is characteristic of zone with D type soil, which is transported alluvial soil. Vs 30 < 180 zones define the limits of the areas affected by floods in the study region.