Microtremor measurements in the northern coast of Izmir Bay, Turkey to evaluate site-specific characteristics and fundamental periods by H/V spectral ratio method

Seventy-two microtremor measurements were conducted in the northern coast of Izmir Bay. The dataset has been processed using the horizontal-to-vertical spectral ratio. The fundamental period contour map obtained showed that the fundamental period at rock sites of the northern coast of Izmir Bay was between 0.15 and 0.35 s. However, the fundamental period increased towards the western direction where thick soft sediments exist, the fundamental period varied between 0.5 and 2.0 s. A soil classification map of the area was prepared based on the data estimated from SPT-N values of 25 boreholes. It is seen that major portion of the study area, including the shore line of the northern coast had SPT-N values lower than 15. The fundamental periods obtained by H/V spectral ratio method and the periods derived from shear wave velocity data available in 11 of 25 boreholes were well-correlated. Fundamental period map obtained from H/V spectral ratio method illustrated the characteristics of weak soil conditions and the presence of bedrock level under thick alluvial soils. Finally, microtremor investigations have proved to be an effective tool for assessment of local soil conditions in case of thick soft sediments in the northern coast of Izmir Bay.