Gravity models of the Wairarapa region, New Zealand

Abstract

Two-dimensional and three-dimensional gravity models of the Mesozoic basement topography in the Wairarapa show that the major feature is the Wairarapa Trough, aligned SSW-NNE through the area. The Trough has two arms, one north of Eketahuna and the other south of Carterton. All three features are fault-angle depressions, bounded to the west by the West Wairarapa, Wellington, and Dry River Faults, respectively, and reaching their greatest depths at these faults. A structural contour map of the Mesozoic surface in the Wairarapa shows that the basement is covered by more than 3000 m of Cenozoic material. The West Wairarapa Fault is shown to be reverse in the south, with a dip as low as 15°. The other faults are apparently near-vertical.

Quaternary faulting in the offshore Flaxbourne and Wairarapa Basins, southern Cook Strait, New Zealand

“…6, profiles A and B). The vertical separation of acoustic basement across the fault is of the order of 1.7-2.0 s TWT (c. 2.0-2.3 km), which is consistent with the displacement predicted from gravity modelling on land (Hicks & Woodward 1978). An absence of fanning stratal geometry into the fault on profile A suggests that the vertical displacement postdates the deposition of the Tongaporutuan sediments.…”

Faults in Cook Strait and their bearing on the structure of central New Zealand

“…Onshore, the West Wairarapa Fault has a distinct structural setting, forming the western margin of a major graben containing up to 2500 m of sediment, determined from gravity data (Hicks & Woodward 1978). 7his same setting is recognisable offshore where the fault exhibits at least 1000 m down throw to the southeast thus defining a more or less continuous sedimentary basin (here called the Wairarapa Basin) that extends to the South Island shelf ( Fig.…”

Using displaced river terraces to determine Late Quaternary slip rate for the central Wairarapa Fault at Waiohine River, New Zealand

“…Because the Wairarapa Fault plane is not exposed in the Waiohine River gorge, we assume a near-vertical fault plane at the Waiohine River on the basis of magnetotelluric and gravity surveys of the Wairarapa Fault (e.g. Hicks & Woodward 1978;Von Borstel & Ingham 2004).…”