Seismic refraction measurements in Fiordland southwest New Zealand

Abstract

Seismic refraction measurements have demonstrated the existence of rocks with lower crustal velocities at shallow depth under central Fiordland. Rocks with compressional wave velocities of 7.3, 6.8, 6.5, 5.7–5.3, and 5.1 km/s have been detected. The rocks with a velocity of 6.8 km/s occur within 3.5 km of the surface, while those with a velocity of 7.3 km/s lie at a depth of about 8 km. No rocks with velocities normally associated with the mantle (>8 km/s) were detected, indicating that they probably lie at depths greater than 15 km. It is suggested that the Fiordland crustal block has been uplifted by at least 10 km in the west and tilted to the east.