Hope fault, Jordan thrust, and uplift of the Seaward Kaikoura Range, New Zealand

Abstract

In the northern South Island of New Zealand, displacement at the Pacific-Indian plate boundary is accommodated by the east-north-east-striking, right-lateral strike-slip Marlborough fault system. The southernmost Marlborough fault is the Hope fault; the late Pleistocene-Holocene horizontal slip rate on this fault is 20-25 mm/yr, about half of the rate of Pacific-Australian plate motion. Near the eastern end of the Hope fault, most displacement is transferred to the north-northeast-striking Jordan thrust, but the average dip-slip rate at the surface trace of this thrust is less than 4 mm/yr. We propose that most slip takes place on a blind thrust, expressed at the surface by the fault-propagation folding of the Seaward Kaikoura Range, and that the rate of uplift of this range is as high as that of the Southern Alps, 6 to 10 mm/yr. The major restraining bend of the Alpine fault has the same average slip rate as the Wairau fault, 4-6 mm/yr. Even though the Alpine fault is an east-dipping, reverse-separation fault at the restraining bend, this low slip rate results in uplift of the Spenser Mountains east of the bend at a rate lower than that of the Southern Alps and Seaward Kaikoura Range.