Monitoring S-wave Velocity of the Ground using Continuous Seismic Ambient Noise Measurements

Synopsis:

S-wave velocity (Vs) of the ground is one of the most important proxies to evaluate geological or geotechnical ground conditions. The Vs is not permanent and changes depending on soil or rock properties such as the changes of water contents or overburden pressure associated with weather condition or underground constructions. We developed a non-invasive monitoring method of the Vs profile from the ground surface using seismic microtremors or ambient noises. The ground surface is always weakly vibrating with seismic surface waves that horizontally propagate along the ground surface generated by various natural and cultural sources such as ocean waves and traffic noise. Propagation velocity of the surface waves depends on Vs profile of the ground, and we can monitor the changes of Vs profile by measuring and processing the seismic ambient noise at the ground surface. Our monitoring system consists of several cableless seismograph with velocity sensors (geophones). Each…