Surface related multiple elimination (SRME) and radon transform forward multiple modeling methods applied to 2D multi-channel seismic profiles from the Chukchi Shelf, Arctic Ocean

The Chukchi Edges project was designed to establish the relationship between the Chukchi Shelf and Borderland and indirectly test theories of opening for the Canada Basin. During this cruise, ~5300 km of 2D multi-channel reflection seismic profiles and other geophysical data (swath bathymetry, gravity, magnetics, sonobuoy refraction seismic) were collected from the RV Marcus G. Langseth across the transition between the Chukchi Shelf and Chukchi Borderland, where the water depths vary from 30 m to over 3 km. Multiples occur when seismic energy is trapped in a layer and reflected from an acoustic interface more than once. Various kinds of multiples occur during seismic data acquisition. These depend on the ray-path the seismic energy follows through the layers. One of the most common multiples is the surface related multiple, which occurs due to strong acoustic impedance contrast between the air and water. The reflected seismic energy from the water surface is trapped within the water column, thus reflects from the seafloor multiple times. Multiples overprint the primary reflections and complicate data interpretation. Both surface related multiple elimination (SRME) and forward parabolic radon transform multiple modeling methods were necessary to attenuate the multiples. SRME is applied to shot gathers starting with the near offset interpolation, multiple estimation using water depths, and subtracting the model multiple from the shot gathers. This method attenuated surface related multiple energy, however, peg-leg multiples remained in the data. The parabolic radon transform method minimized the effect of these multiples. This method is applied to normal moveout (NMO) corrected common mid-point gathers (CMP). The CMP gathers are fitted or modeled with curves estimated from the reference offset, moveout range, moveout increment parameters. Then, the modeled multiples are subtracted from the data. Preliminary outputs of these two methods show that the surface related multiples were well attenuated. The multiple attenuated CMP gathers were further enhanced by stacking, where there are increasing stacking velocity and normal moveout range differences between the primary and secondary reflections. The multiple attenuated seismic profiles more clearly reveal extensive shelf margin progradation from the Chukchi Shelf towards the NW. This unit probably formed during post-rift subsidence and may provide new contraints on the timing and extent of rifting. Deeper reflectors are also enhanced by stacking, which shows continuous reflectors parallel to the acoustic basement, and pre-rift stratified sediment (?) packages, which pre-date the East-West extension in the area. These older units, of very uncertain age, would, if sampled, provide constraint on the history and affinities of the Chukchi Borderland.