Abstract
In this paper, we demonstrate that common midpoint spatial autocorrelation (CMP-SPAC) analysis of multichannel passive surface waves gives accurate phasevelocity curves, and enable us to reconstruct twodimensional (2D) S-wave velocity (VS) structures with in laterally heterogeneous environment. Recording geometry for CMP-SPAC analysis is similar to that used for multichannel analysis of surface waves (MASW). Ten to twenty minutes of vertical component ambient noise is recorded and divided into several blocks for spatial autocorrelation (SPAC) analysis. Processing of CMP-SPAC data consists of four steps: First, SPAC traces are calculated for every pair of receivers in each ambient noise block. Second, the SPAC traces are averaged over all blocks in the frequency domain and the SPAC traces having a common mid-point are sorted into CMP-SPAC gathers. Third, dispersion curves are calculated from each CMP-SPAC gather by comparing observed coherences with theoretical Bessel functions. Finally, a 2D VS section is reconstructed through non-linear least squares inversion. The method was applied to actual field data and compared with active surface wave data. The results from CMP-SPAC analysis using passive surface wave data are almost identical to those from common midpoint cross-correlation (CMPCC) analysis using active surface wave data. This suggests that active sources are not needed for surface wave data acquisition methods in many cases. The use of the CMP-SPAC method with passive data has the potential to greatly improve the efficiency and applicability of surface wave methods.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call