Late Quaternary faulting

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New Zealand Geological Survey 1966 Late Quaternary faulting. Lower Hutt: New Zealand Geological Survey. Report NZGS 7; New Zealand Geological Survey report EDS 1. 9 p.


In the study of late Quaternary faulting, a major problem confronting geologists and engineers is to decide which faults should be classed as active. In making his assessment of the probability of future movement, the geologist is guided by the basic principle that the past provides a key to the future, so that a fault that has moved repeatedly in the past is likely to move with similar frequency in the future. In making his assessment, however, the geologist is limited by the evidence he has seen in the field. He may observe many different types of evidence of faulting, but the geological record is far from perfect. His deductions are incomplete, and may need revision in the light of later additional evidence. The geologist can map the positions of faults and can also distinguish a great range of large and small faults. Th problem is to devise a classification that will usefully indicate the magnitude and frequency of past earth movements and so be a guide to the likelihood of future movements. At places along any one fault, the geologist may be able to estimate the total displacement. By observing the cumulative displacement of flights of river terraces etc, he can conclude that many faults have moved repeatedly. He can also determine the minimum number and the possible magnitude of individual movements that together are responsible for the inferred total displacement. By studies of the development of the landscape, particularly of terraces, and by using radiocarbon and other dating methods, the geologist can form an opinion of the relative age of the individual surfaces cut by the fault. He can therefore estimate broadly the time at which some individual fault movement took place. (auth)