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Several geophysical methods exist to delineate the lower interface of a sedimentary basin. Most popularly employed are gravity and magnetic surveys and surface-wave inversion. While all three methods are successful overall in estimating an average basin depth, they fail to find a more detailed depth variation. As an alter-native, we consider three passive seismic techniques, using especially body waves. We analyze 40 hours of data, recorded with 110 stations installed over the Abu Gharadig basin in Egypt. In an earlier study we found the frequency band of 0.09-1.0 Hz to be dominated by body waves. As a first method we apply body-wave seismic interfero-metry (SI). Using body-wave noise, we extract PP and SS reflections from the basin floor. We estimate the depth of the basin to be around 4.8 km. As a second technique we estimate the resonance spectra of the basin, using the horizontal-to-vertical (H/V) spectral ratio. Using surface-wave noise, we find an extremum that is probably related to the complete sedimentary package. Using this peak, we find a basin depth of 5.4 km. Using S-phase arrivals, we find two extrema in the H/V, which are probably related to the S-wave resonances of two distinct layers in the basin. As a third method we compute receiver functions (RFs). Based on the RFs, we can confirm the presence of a large interface in the upper crust, but we cannot well constrain its depth. [ABSTRACT FROM AUTHOR]

Deblending of simultaneous-source data is usually considered to be an underdetermined inverse problem, which can be solved by an iterative procedure, assuming additional constraints like sparsity and coherency. By exploiting the fact that seismic data are spatially band-limited, deblending of densely sampled sources can be carried out as a direct inversion process without imposing these constraints. We applied the method with numerically modeled data and it suppressed the crosstalk well, when the blended data consisted of responses to adjacent, densely sampled sources. [ABSTRACT FROM AUTHOR]

We have analyzed the far-field approximation of the Green's function representation for seismic interferometry. By writing each of the Green's functions involved in the correlation process as a superposition of a direct wave and a scattered wave, the Green's function representation is rewritten as a superposition of four terms. When the scattered waves are modeled with the Born approximation, it appears that a three-term approximation of the Green's function representation (omitting the term containing the crosscorrelation of the scattered waves) yields a nearly exact retrieval, whereas the full four-term expression leads to a significant nonphysical event. This is because the Born approximation does not conserve energy and therefore is an insufficient model to explain all aspects of seismic interferometry. We use the full four-term expression of the Green's function representation to derive the generalized optical theorem. Unlike other recent derivations, which use stationary phase analysis, our derivation uses reciprocity theory. From the generalized optical theorem, we derive the nonlinear scattering matrix of a point scatterer. This nonlinear model accounts for primary and multiple scattering at the point scatterer and conforms with well-established scattering theory of classical waves. The model is essential to explain fully the results of seismic interferometry. even when it is applied to the response of a single point scatterer. The nonlinear scattering matrix also has implications for modeling, inversion, and migration. [ABSTRACT FROM AUTHOR]

The article discusses various papers published within the issue including one about a new application of seismic interferometry to field data and another on the effect of seismic anisotropy on a single-well acoustic-reflection survey and on reflection imaging.

Seismic interferometry refers to the process of retrieving new seismic responses by crosscorrelating seismic observations at different receiver locations. Seismic migration is the process of forming an image of the subsurface by wavefield extrapolation. Comparing the expressions for backward propagation known from migration literature with the Green's function representations for seismic interferometry reveals that these seemingly distinct concepts are mathematically equivalent. The frequency-domain representation for the resolution function of migration is identical to that for the Green's function retrieved by seismic interferometry (or its square, in the case of double focusing). In practice, they differ because the involved Green's functions in seismic interferometry are all defined in the actual medium, whereas in migration one of the Green's functions is defined in a background medium. [ABSTRACT FROM AUTHOR]

Acoustic, electromagnetic, elastodynamic, poroelastic, and electroseismic waves are all governed by a unified matrix-vector wave equation. The matrices in this equation obey the same symmetry properties for each of these wave phenomena. This implies that the wave vectors for each of these phenomena obey the same reciprocity theorems. By substituting Green's matrices in these reciprocity theorems, unified wave field representations are obtained. Analogous to the well-known acoustic wavefield representations, these unified representations find applications in geophysical modeling, migration, inversion, multiple elimination, and interferometry. [ABSTRACT FROM AUTHOR]

The article discusses various reports published within the issue including one by Felix J. Herrmann, Deli Wang, Gilles Hennenfent and Peyman P. Moghaddam on the applications of curvalet-domain sparsity promotion and another by Christopher Liner on the use of sand curve to correct land seismic data for large time delays arising from sand dunes.