Document Type : Research Article
Authors
1
M.Sc. Student in Geotechnical Engineering, Department of Civil Engineering, Mashhad Branch, Islamic Azad University, Mashhad, IranDepartment of civil engineering Islamic Azad university of Mashhad
2
Assistant Professor, Department of Civil Engineering, Mashhad Branch, Islamic Azad University, Mashhad, Iran
3
Ph.D. Candidate, Department of Civil engineering, University of Memphis, Memphis ,TN, USA
4
M.Sc. Student in Geotechnical Engineering, Department of Civil Engineering, Mashhad Branch, Islamic Azad University, Mashhad, Iran
Abstract
This article presents a parametric analysis of the dimensions and geometry of trapezoidal alluvial valleys, specifically examining the effects of valley ridge angle on the linear seismic response of alluvial valleys. This analysis uses the NASEM dynamic program, based on spectral elements, to assess responses to incoming longitudinal and shear waves. Previous research on the effects of topography on ground surface seismic response has shown the significant influence of these topographic features' geometry on seismic response. The results demonstrate that the amplification pattern and natural frequency of a trapezoidal alluvial valley are highly dependent on the valley ridge angle. As the valley ridge angle decreases, the natural frequency of the valley also decreases, trending toward the natural frequency associated with a homogeneous soil layer over bedrock under longitudinal waves, and similarly under shear waves. An increase in the parameters of valley ridge angle, valley bottom width, alluvial thickness, and longitudinal wave velocity results in a corresponding rise in the valley's natural frequency.
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