Rotational Data Measurement

Rotational components just below the free-surface can be estimated by differencing closely spaced vertical geophones. This is particularly convenient because dedicated rotational sensors do not yet have the high sensitivity and robustness for commercial use in the seismic industry. In this paper, we show that this new data type contains highly desirable information about the seismic wavefield. For instance, they provide a direct measurement of the ray parameter, or equivalently, the apparent velocity of the vertically polarized wavefield. Compared to conventional traveltime methods, this has the advantage of being completely local and, therefore, does not require long and dense arrays of receivers to be deployed. Potential applications include, among others, wavefield interpolation, wavefield decomposition, near-surface characterization and ground-roll attenuation.