A maximum subsidence and shortening rate of 0.2 ± 0.05 mm/yr is calculated for the Pliocene-Pleistocene section of Cannington Basin, South Canterbury, New Zealand. This estimate is based largely on geophysical data. Strong, coherent seismic reflections down to 1.0 s two-way travel time were recorded within the basin. Seismic velocities within the basin range from 1.9 to 4.4km/s, and seismic refraction data show a depth of c. 1200 m to a basement with a velocity of 5.6 ± 0.1 km/s. Within the top 600 m of the sedimentary section, seismic velocities are <2.3 km/s, which we interpret to be the Pliocene-Pleistocene section. Residual gravity anomalies within the basin are as low as -20 mgal and are asymmetrically disposed to the eastern side of the basin against a sharp topographic scarp-the Brothers Fault. About 300 m of topographic relief is present on this 30-40 km long scarp. We propose that the Brothers Fault has been active from the Pliocene until the present as a reverse fault with dip inferred to vary between 80° and 50°. This interpretation is based on the steepness of the residual gravity anomalies across the Brothers Fault scarp, the seismically interpreted thickness of Pliocene-Pleistocene sediments across the fault, and the observations of tilting of late Pliocene sediments on the hills that flank the eastern margin of Cannington Basin.
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