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Role of Fracturing on Seismic Noise Measurements - The Case of the Bory Crater (La Réunion Island)
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, Near Surface Geoscience 2015 - 21st European Meeting of Environmental and Engineering Geophysics, Sep 2015, Volume 2015, p.1 - 5
Abstract
In recent years, ambient seismic noise measurements have significantly developed in gravitational hazard assessment for both investigation and monitoring purposes. The wide frequency range allows ambient vibrations to be applied for investigating geological and civil engineering structures in a great variety of sizes, from the lithospheric or crust scale to a few m-thick landslide and rock column or buildings. On landslide sites, several studies revealed significant spectral amplification at given frequency and polarization of the wave-field in the direction of maximum slope displacement. They show that different characteristics (resonant frequencies, polarization, and spectral amplification) could be used from the spectral analysis of the ambient motion or from spectral ratios for characterizing landslides.
This study aims to study a prone-to-fall column located at the top of a basaltic cliff in the Bory Crater (Réunion Island). Seismic prospecting profiles were performed on the plateau to characterize the basaltic lava deposits and the ambient seismic noise was measured using 3C sensors located on the column and at several distances from the cliff. The studied showed a clear resonance effect due to the column vibration, as well as larger site effect which could be related to the fracturing in the Bory crater.