Continous deformation versus faulting through the continental lithosphere of New Zealand

Seismic anisotropy and P-wave delays in New Zealand imply widespread deform ation in the underlying mantle, not slip on a narrow fault zone, which is c haracteristic of plate boundaries in oceanic regions. Large magnitudes of s hear-wave splitting and orientations of fast polarization parallel to the A lpine fault show that pervasive simple shear of the mantle lithosphere has accommodated the cumulative strike-slip plate motion. Variations in P-wave residuals across the Southern Alps rule out underthrusting of one slab of m antle Lithosphere beneath another but permit continuous deformation of Lith osphere shortened by about 100 kilometers since 6 to 7 million years ago.