Dual seismic fields from distributed acoustic sensors

Distributed acoustic sensors (DAS) using fiber optic cables is an emerging acquisition technology for O&G industry. It offers the advantage of improving seismic acquisition by massive monitoring of seismic waves at reduced cost. In this paper we show that, as a result of the dense spatial distribution of recording points along the optic cable, DAS can provide two field components in the axial direction, even when using a single one-dimensional line. These signal pairs consist of dual components, which are related to strain and particle velocity fields at a given recording location. We show with real examples where the data can be combined to provide separation of up- and down-going wavefields. The ratio of the dual components provides information on local slowness properties in the formation.