The Evaluation of Alluvial Thickness in Mashhad City Using the Microtremore study

The present study shows that the frequency of the main peak in the spectral ratio analysis of microtremores data correlates well with the sediment thickness at the many sites. In this study, based on the resonance period of microtremores in 200 points estimated by H/V spectral ratio and the shear wave velocity profile of 62 points the power relationship of between the thickness of sediments and resonance period in Mashhad city are introduced and the iso-thickness sediments map and cross sections are produced. The results show that the maximum thickness of the soft sediments is about 200 meters in south-east and central of Mashhad and its decreases to the south, south-west and north mountains area.