Vibration Analysis
Seismic noise monitoring is relevant to any discipline that depends on seismology, such as geology, oil exploration, hydrology, and earthquake engineering, and structural health monitoring. These vibrations allow observation of the global response for a structure, including damage detection, classification, and progressive development. It is often called ambient wavefield or ambient vibrations in those disciplines. It is also used to influence the estimation of the vibrational load on the foundation of a building and its soil. The analysis of the ambient vibrations leads to different products used to characterize the ground properties.
Data Acquisition
Generally, the measurements of earth vibration is carried out at given sites (i.e. grid points) with a minimum distance of 50-200 meter between recording points. The orthogonal high-resolution electro dynamic sensors (10 sec) is utilize. At each site, the passive earth vibration will be registered for at least 1-2 hrs duration. The site amplification of ground motion is primarily attributed to either the geomorphological features that produce scattering, focusing, or defocusing of incident energy (topographic effect) or thick alluvium-filled terrain that causes reverberations due to trapped energy (basin effect). Technique used widely to quantify site response in terms of site amplification factors includes Horizontal-to-Vertical Spectral Ratio (HVSR).