Abstract: Methods and systems are disclosed to enhance surveying techniques. In one embodiment, a virtual response is estimated that corresponds to energy propagated within a subsurface region between a virtual source and a virtual source estimation receiver, wherein the subsurface region corresponds to a survey zone including: a plurality of receivers deployed within the survey zone, a first subzone having at least one actual source, a second subzone within the first subzone; the virtual source is a first receiver disposed in the second subzone; and the virtual source estimation receiver is a second receiver.

Abstract: An embodiment of the invention includes combining pseudorandom sweeps with an independent, or nearly independent, survey acquisition technique. Targeted design of pseudorandom sweeps can direct the majority of cross-correlation noise to lie outside key time-lags of the record (i.e., windows of interest). Embodiments of the invention are described herein.

Abstract: An embodiment of the invention includes combining pseudorandom sweeps with an independent, or nearly independent, survey acquisition technique. Targeted design of pseudorandom sweeps can direct the majority of cross-correlation noise to lie outside key time-lags of the record (i.e., windows of interest). Embodiments of the invention are described herein.

Abstract: Methods and systems are disclosed to enhance surveying techniques. In one embodiment, a virtual response is estimated that corresponds to energy propagated within a subsurface region between a virtual source and a virtual source estimation receiver, wherein the subsurface region corresponds to a survey zone including: a plurality of receivers deployed within the survey zone, a first subzone having at least one actual source, a second subzone within the first subzone; the virtual source is a first receiver disposed in the second subzone; and the virtual source estimation receiver is a second receiver.

Abstract: A seismic source array 15 comprises a plurality of seismic source 26 arranged about a central point of the source array 15 in such a way that an imaginary circle drawn with said central point at its center, and containing all of said seismic sources 26, can be divided into at least three whole sectors each of which contains a substantially identical arrangement of seismic sources 26.

Abstract: A seismic source array 15 comprises a plurality of seismic source 26 arranged about a central point of the source array 15 in such a way that an imaginary circle drawn with said central point at its centre, and containing all of said seismic sources 26, can be divided into at least three whole sectors each of which contains a substantially identical arrangement of seismic sources 26.

Abstract: Methods and apparatus for seismic data compression are described, making use of a local discrete sine/cosine transform of the type IV applied to a data set which is limited by a stationary window function which reduces the overlap to the adjoining windows.

Abstract: The method includes the steps of applying a local spatial trigonometric transformation to seismic data to generate transformed data and compressing the transformed data. Compression may be achieved by retaining a selected part of the transformed data at reduced accuracy. The selected part may be a high frequency part of the transformed data. A window function is chosen so that the transformations are applied over a central window and overlap with the adjoining windows. Suitable transformations for use with the method include a local cosine transformation, a discrete cosine transformation of type IV, a local sine transformation and a Fourier transformation. For example, a HF part of the transformed data is retained at reduced accuracy. The transformed data is compressed by a coarser re-quantization of the transformed data. A temporal transformation is applied to the seismic data, that is local and of the trigonometric type.