Alexander McKay and the Awatere Fault, New Zealand: ground rupturing and large-scale horizontal displacement

Abstract

In 1888-89, Alexander McKay, Assistant Geologist of the New Zealand Geological Survey, defined the Awatere Fault, one of the four major dextral strike-slip faults in the Marlborough area that constitute the Australia-Pacific plate boundary in northeastern South Island of New Zealand. McKay began tracing and describing active faulting in New Zealand in 1885 and his observations were fundamental in clarifying the relationship between superficial earthquake-rents or fissures and faults, and that faults have long displacement histories. Along the Awatere Fault, he determined the nature of the faulted contact between late Miocene, Cretaceous to early Tertiary rocks and Mesozoic greywacke, vertical displacement of Quaternary alluvial gravel surfaces, and confirmed evidence for repeated movement on the fault. For the first time anywhere in the world, McKay's work on the Awatere Fault suggested the possibility of large-scale strike-slip displacement (of 29-32 km). McKay took several photographs of the Awatere Fault using a telephoto lens that he had invented, and which is explained.