Comparing continuous profiles from MASW and shear-wave reflection seismic methods

• High resolution shear wave reflection acquisition using land streamers
• MASW acquisition using land streamer
• 2-D continuous profiling of MASW and shear wave reflection
• Comparative analysis of 2-D continuous profiles of MASW and shear wave reflection

We use the seismic shear-wave reflection and multichannel analysis of surface wave (MASW) methods to examine if the MASW profiling can be an alternative for the shear-wave reflection method for near-surface characterization at specific subsurface settings. The shear wave reflection method does not work well in noisy areas, takes longer time for data acquisition and requires excessive post acquisition processing compared to the MASW method. Two surveys were conducted using land streamer technology along two lines totaling 3.7 km in southern Illinois. The reflection data were used to generate seismic reflection profiles. The stacking velocities along the reflection profiles were converted into interval velocities and mapped as 2D velocity images. The MASW data were used to generate continuous 2D shear-wave velocity (Vs) profiles. The MASW and the stacking-derived interval velocity images provided a smeared image of the overlying sedimentary layers and did not image small-scale features, such as igneous intrusions and near-surface faults. However, the MASW 2D Vs profiles and the reflection profiles compared well in mapping the bedrock surface and the thickness of the overlying unconsolidated sediment. The results confirmed that the MASW method can be an alternative to the reflection method when the survey target and near-surface conditions allow.