Woodlark Basin Tomography

Woodlark Basin

The western Woodlark Basin of Papua New Guinea is one of the best examples of active continental rifting that transitions laterally to seafloor spreading. The rift zone contains active or recently uplifted metamorphic core complexes and a major east-west trending, shallowly-dipping normal fault, which has exhumed a large, footwall block known as Moresby Seamount. In 1999, I participated on an active and passive seismic investigation of the Woodlark rift immediately ahead of the propagating tip of the seafloor spreading center. We fired a total of 3607 airgun shots using a tuned 10,800 cu. in. array of 20 airguns aboard the R/V Maurice Ewing. The airgun shots were recorded by marine seismometers and hydrophones positioned within the rift zone to the north of Moresby Seamount and by land seismometers installed on islands surrounding the rift zone. Compressional wave seismic traveltimes to the combined land and marine arrays were used to invert for the three-dimensional seismic velocity structure of the rift zone. The images reveal the depth extent of the rift zone detachment to a depth of ~15 km and a high velocity body, which suggests the presence of magmatic upwelling in the crust west of the propagating Woodlark spreading center.

Publication: Floyd, J., Seismotectonics of Mid-Ocean Ridge Propagation, Ph.D. Thesis, Columbia University, 2003.