Directional variations of site response in a landslide area using ambient noise analysis via Nakamura’s and polarization-based method: Fid-Bau Portal

Directional variations of site response in a landslide area using ambient noise analysis via Nakamura’s and polarization-based method

Kazemnia Kakhki, Mohsen / Del Gaudio, Vincenzo / Rezaei, Sadegh / Mansur, Webe João

Abstract

Abstract The complexity of the NE Iran region in which the 2014 Nargeschal landslide occurred, increased the necessity of detailed survey on the site response properties of this region. New investigations expanded the set of ambient noise measurements acquired in a previous work on the area affected by mass movement. The outcome of electrical resistivity and geotechnical studies were used to provide a comprehensive model of the landslide in addition to the substratum geology. The ambient noise recordings were analysed using the well-established Nakamura’s method and a recently devised approach based on the analysis of the Rayleigh wave ellipticity to provide more detailed information on site resonance properties characterized by directional variations. The outputs, which were compared with the results of electrical resistivity tomography and geotechnical investigations, showed the better performance of the latter method in terms of stability and reliability of the results. Indeed, it allowed to detect site resonance characteristics that were unrecognizable by the Nakamura’s method. Conclusively, the ambient noise analysis reveals that the directional resonance on different parts are due to the landslide and structural features of the site. The information obtained in this work is relevant for seismic hazard assessment in the study area.

Highlights • The polarization analysis has more advantages than the Nakamura’s method. • The analysis of the Rayleigh wave ellipticity provide more information on site resonance properties. • The outputs are more stable and reliable of the results. • The electrical resistivity and geotechnical studies used for a comprehensive model of the landslide. • The geological and structural features of the site are responsible for the directional resonance.