The above diagram shows the free-air gravity for the Solomon Island-OJP region. The white outline of the OJP is the 4000 m isobath. The linear white lines represent paleomagnetic data from the adjacent ocean basins. The black circles denote the locations of ODP/DSDP drill sites. A geologic age in parentheses beneath the site number indicates drill sites where basalt was penetrated and the corresponding age of that basalt. One intersting feature on this map is the 35-50 mgal high located on the OJP's southwestern edge just north of the North Solomon Trench. This anomaly is associated with flexuring of the OJP as it enters the NST.
Hypocenter profiles A, B, and C are shown below. Note that on all the profiles there is not much seismicity below 200 km. We also see a decrease in seismic activity on Profile B relative to A and C. This inactivity is correlated with northeast subduction of the Woodlark Spreading Center, an active spreading ridge. Also of importance are the well-defined southwest-dipping Wadati-Benioff zones on Profiles B and C. These indicate current activity in the previously subducted Pacific plate.
One of the many remaining unsolved problems in this area is the sub-arc plate geometries between the Australian and Pacific plates.
View seismic
data examples from our survey
Back to
Malaita Accretionary Prism page