Part of the EW95-11 marine seismic survey aboard the R/V Maurice Ewing consisted of over 2 km of 120-channel data from 18 lines covering the Malaita Accretionary Prism. The maximum recording offset was 3.2 km with a receiver group interval of 25 m. The source consisted of a 20 airgun array with over 8300 cu. in. displacement.
All seismic lines have undergone a preliminary processing sequence including a weighted stack for multiple attenuation and f-k migration at a constant velocity of 1500 m/s. More intensive processing sequences, such as DMO, deconvolution for bubble pulse attenuation, other multiple attenuation techniques, and f-x migration, have been applied to certain areas of interest from some of the lines.
Below are links to several seismic images. The SBT reflector indicated on the seismic sections marks the Mid-Cretaceous change from pillowed and massive basalts to overlying siliceous mudstone or pelagic limestone. This sediment-basalt transition is a huge impedance contrast and the resulting reflection is easy to trace from the OJP up onto the prism. The list of seismic sections are presented from SE to NW. Moving from Line 3b to the northwest, we see a shallowing of the North Solomon Trench with a decrease in dip of the prism's inner trench wall and a decrease in dip of the incoming OJP. We also see a distinct change in accretionary style correlated with a shallowing in depth to the basal decollement.
The important point to keep in mind as we move from the SE to the NW is that we are going from an area that has undergone several million years of plateau accretion into areas that have undergone virtually no plateau accretion. Again, this is directly related to the OJP's approach from the east.
Look
at MAP structural zone map
Line 3b -
southern edge of MAP
Line 1
OJP/MAP transition
Ontong Java Plateau close up
Line 26
Recent sediment deformation
Decollement
Back to
Malaita Accretionary Prism page