High-resolution imaging of diffractions — A window-steered MUSIC approach

Abstract

Enhancement of diffractions and their use to resolve finescale details in a seismic image is increasingly important. Diffractions carry useful information about small-scale characteristics of the subsurface associated with features such as faults, pinch-outs, stratigraphic variations, and other geologic features linked to hydrocarbon reservoirs. Extracting the information content of diffractions and forming an image of the features they illuminate are not trivial tasks. The conventional approach relies on seismic migration, or modifications of seismic migration, and is thus limited by the Rayleigh criterion. The limited aperture and finite bandwidth make it difficult to extract all the potential information content. An alternative approach that overcomes such limitations is to turn to signal processing approaches, which extract information from the structure of the data with the aim of detecting and characterizing a finite number of desired events. Our interest is in diffractions, so we used a windowed or steered version of the MUltiple SIgnal Classification method. Use of this method allowed diffractions to be imaged at resolutions finer than the Rayleigh limit.

On Beamforming of DAS Ambient Noise Recorded in an Urban Environment and Rayleigh‐To‐Love Wave Ratio Estimation

“…We use the MUSIC beamforming technique (Gelius et al., 2013; Godara, 1997; Goldstein & Archuleta, 1987; Kirlin, 1992; Zhang et al., 2019) to estimate the ambient noise source propagation direction. The beamforming spectrum can be calculated from the seismic data or the corresponding common virtual‐shot gather.…”

“…By observing the polarity of the common virtual‐shot gather at the corner of the DAS array, we determine whether there is polarity reversal and apply a polarity flip to the common virtual‐shot gather when polarity reversal occurs. After that, we apply multiple signal classification (MUSIC) beamforming (Gelius et al., 2013; Godara, 1997; Goldstein & Archuleta, 1987; Kirlin, 1992; Zhang et al., 2019) on the extracted common virtual‐shot gathers. We demonstrate that beamforming results obtained from the DAS ambient noise data after amplitude normalization and polarity correction are reliable when the source direction is unique.…”

Vertical Seismic Profile Complete Session

“…Its reciprocal has a peak in the MUSIC pseudo-spectrum, for example calculated as (Gelius et al 2013)    , The minimization condition for a suitable subset of small eigenvalues is satisfied when the steered signal is properly aligned by the traveltimes of the scatterers, and the steered noise subspace projection is zero.…”