Diffraction velocity analysis in a single-channel seismic survey in the Joetsu Basin

Abstract

Historically, marine research has been using single-channel seismic (SCS) devices for scientific projects. Despite SCS’s abundant data availability and the contribution it has brought for subsurface comprehension, few efforts have been dedicated to improve the SCS processing flow to extract more information carried by seismic signals and for better imaging. Diffractions present the necessary means to estimate sediment acoustic properties useful for imaging, stability studies, and geohazard prevention. The root-mean-square (rms) velocity is estimated from diffractions using a diffraction velocity analysis workflow composed of the following main steps: separation of diffractions from specular events using stationary phase properties and plane-wave destruction filtering, determination of diffractor locations in time, velocity scanning using constant rms velocity time migration, automatic picking of rms velocity at the diffractor location in the scan volume, and quality control to avoid spurious rms velocity. The method circumvents the sparsity and nonuniform distribution of diffractions for smooth lateral velocity change conditions. Application in a SCS line acquired in the Joetsu Basin, Japan Sea, indicates improvement in the focusing of deeper events compared to the previous processing flow, and it adds consistent information about the acoustic properties of the subsurface.