Estimation of ground types in different districts of Gümüşhane province based on the ambient vibrations H/V measurements

Abstract

In this study, an attempt was made to estimate the ground types for Torul, Kürtün, Kelkit, Şiran and Köse districts of Gümüşhane, Turkey, by analyzing the predominant frequency and H/V ratio from microtremor data through the single station microtremor H/V ratio of Nakamura technique. For all districts, predominant frequencies show a general distribution between 1.36 and 9.84 Hz, H/V ratios between 1.01 and 9.58. According to these variations, three transient zones can be suggested as i) Z1, stiff rock composed of gravel, sand and other soils mainly consisting of tertiary or older layers with period of 0.1 to 0.2s, ii) Z2, sandy gravel, stiff sandy clay, loam or sandy alluvial deposits whose depths are 5m or greater with period of 0.2 to 0.4s, and iii) Z3, standard grounds other than type Z1, Z2 or Z4 (alluvial deposits whose depths are 5m or greater) with period of 0.4 to 0.8s. These results suggest that predominant period obtained from predominant frequency shows significant changes based on the soil formation, and H/V ratio highly corresponds to these subsurface properties. Soil-structure interaction can also be evaluated by considering these results and possible resonance risk can be investigated for building resonant frequency in these residential districts in the next. Thus, this type of application and evaluation of microtremor data may provide primary and useful information for other geophysical, geological and geotechnical studies such as planning the seismic resistant infrastructure, detecting the small-scale seismic risks and making a suitable and reliable seismic hazard microzonation in Gümüşhane.