Late Quaternary strike slip on the eastern part of the Awatere fault, South Island, New Zealand

Abstract

New Zealand straddles the obliquely convergent boundary between the Pacific and Australian plates. In central South Island, plate motion is accommodated by oblique collision of continental crust along the Alpine fault in the Southern Alps, and in North Island by subduction of oceanic crust beneath the continental Hikurangi margin. Between these two zones, oblique convergence is accommodated across the ∼150-km-wide Marlborough fault system, which is transitional between the two different styles of margins. Dextral slip in the Marlborough fault system is partitioned among four principal faults, of which the Awatere fault is one. Our data on the eastern part of the Awatere fault provide insight into styles of surface faulting and active deformation in continental transpression zones. We (1) document the segmentation and kinematics of oblique slip on the fault, including a discrepency between long-term and short-term accumulation of vertical motion; (2) describe an along-strike gradient in the degree of slip partitioning of oblique plate motion; (3) measure late Quaternary strike-slip rates of 6–8 mm/yr at several sites along the fault, rates that decrease eastward to