The North Canterbury earthquake of September 1, 1888

Abstract

On September 1, 1888, an earthquake of probable magnitude M7–7.3 struck the Amuri District of North Canterbury, 100 km north-west of Christchurch, New Zealand. The earthquake ruptured a segment of the Hope Fault, and damaged buildings over a wide area. The effects of the earthquake indicate Modified Mercalli intensities of MM IX in the epicentral area. High-intensity isoseismals (>MM VII) were strongly elliptical and parallel to faulting, apparently attenuating steeply to the northwest and southeast, respectively. However, in parts of Greymouth and Christchurch, shaking was amplified (to MM VII), presumably by local ground conditions. After the earthquake, dextral offsets of between 1.5 and 2.6 m were observed on fencelines crossing the Hope Fault at four localities in the Hope Valley. Recent field work has indicated that the ruptured section forms a structurally distinct segment — the Hope River Segment — of the fault. It extends 30±5 km along the Hope Valley, between two basins developed at releasing bends in the Hope Fault zone. I infer that the earthquake was initiated beneath the Hope-Boyle Basin at the western end of the Hope River Segment, and propagated eastward until it was stopped in the Hanmer Basin. These inferences are supported by contemporary accounts of the effects of the earthquake, and are consistent with observations of earthquake faulting documented in recent international studies.