Abstract

Rupturing along part the Hope Fault during a large earthquake in 1888, North Canterbury region, South Island of New Zealand, caused fence lines that crossed the fault to be laterally displaced by 1.5–2.6 m. The offset fence lines were documented (photographed, mapped, and published on) by the Government geologist, Alexander McKay, and forgotten. In the same year, observations of another fault line, the Awatere Fault, in the Marlborough area, South Island, led McKay to propose large-scale lateral displacement of ∼ 29–33 km of geological formations along the fault, the result of cumulative movement of many earthquakes over millions of years (ca. 7 Ma). This ‘revolutionary’ idea was never published. The significance of McKay’s observations/deductions of small- and large-scale lateral displacement on faults was not fully appreciated in New Zealand until 1955 when aerial photography revealed that displacement of geomorphic features intersecting fault lines is dominantly horizontal rather than vertical. The idea of large-scale horizontal movement of the Earth’s crust, for example 483 km of lateral displacement of geological formations along the Alpine Fault in New Zealand first proposed in 1949, is now an integral part of the reigning paradigm of plate tectonics theory that explains the dynamics of movement of the Earth’s crust.