Joint acoustic and separated-elastic least-squares reverse time migration for simultaneously using water-land dual-detector data

In marine seismic exploration, water-land dual-detector observation system is developed to record the acoustic pressure fields by water detectors and the elastic displacement wave fields by land detectors. The water-land dual-detector data sets are usually applied to suppress the multiples. We propose a joint acoustic and decoupled-elastic least-squares reverse time migration (ADE-LSRTM) by jointly using the acoustic pressure and elastic displacement data sets. In this method, acoustic equations are used to calculate the forward-propagated and backward-propagated pressure wavefields in the seawater based on water detector data sets, and decoupled elastic equations are applied to produce the displacement wavefields in the underlying elastic medium. At the seabed interface, a stable acoustic-elastic control equation is used to ensure that the stress wavefields in the sub-seabed and the pressure wavefields in the seawater are transmitted continuously and steadily. In addition, to suppress the severe scattering wave caused by the rugged seabed, we mesh the acoustic-elastic model into curvilinear grids and use a corresponding coordinate transformation to calculate the wavefieds in an auxiliary coordinate system. Two numerical examples suggest that the proposed curvilinear coordinated ADE-LSRTM based on water-land dual-detector data can produce accurate images in P- and S-component with higher efficiency and accuracy.