Figure 4. Stacked, migrated, and depth-converted 196-channel (EW95-1369) and 148-channel (EW95-1374) seismic sections collected with a 5-km streamer across the rift basin north of Moresby Seamount that is the locus of current deformation ahead of the Woodlark spreading center (the western tip of the neovolcanic zone is hatched in the inset). There is no vertical exaggeration. The bounding low-angle normal detachment wraps around Moresby Seamount and has a true dip of 27° 3° toward 015°. Structure contours from 3 to 9 km depth are shown in the inset, with bathymetric contours labeled in hundreds of meters. The antithetic hanging wall normal fault dips south at 45°. On line EW95-1369 the planar detachment (curvi-planar in three dimensions) is imaged over the full depth extent of the seismogenic zone (3—9 km) determined from earthquake waveform inversion results (Abers et al., 1997). Miocene strata on the southern flank of the pre-rift forearc basin dip north at ~10% beneath the northern margin. Figure modified from Taylor et al., (unpubl. data) to show the location of Sites 1108, 1112, and 1113.

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