Three-Dimensional Ambient Noise Tomography Based on Common Midpoint Spatial Autocorrelation
K. Hayashi and C. Konishi
Event name: 24th European Meeting of Environmental and Engineering Geophysics
Session: New Technologies, Developments and Research Trends II
Publication date: 09 September 2018
Info: Extended abstract, PDF ( 3.09Mb )
Price: € 20
We developed a passive surface wave method that delineates 2D or 3D near-surface S-wave velocity (VS) structure from ambient noise obtained from dozens of receivers on the ground surface. A new cableless (nodal) seismograph that includes CPU, A/D converter, GPS clock, Wi-Fi, batteries and SD card was developed and used for data acquisition. The GPS clock permits units to be synchronized over any distance without cables. Ambient noise was recorded using a receiver spacing small enough to avoid spatial aliasing. A common midpoint spatial autocorrelation (CMP-SPAC) method was used to process ambient noise. First, coherencies were calculated for all pairs of receivers. Next, coherencies having common midpoint (CMP) were grouped together and a dispersion curve was calculated at each CMP. A one-dimensional inversion with horizontal constraint was used to estimate a 2D or 3D VS model. This paper summarizes the equipment and method and provides a field example.