Stream Responses to Uplift, Northern Canterbury, New Zealand

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New Zealand streams near the Hope fault have responded rapidly to late Quaternary uplift and climatic changes, and thus are ideal for the development of new concepts. These powerful streams cut broad straths in bedrock at about 30,000 years ago, and at the present. Confirmation of the 30,000 years age estimate, and measuring amounts of stream-channel downcutting since then, will (1) identify active faults and folds and (2) provide the data for a regional map of late Quaternary uplift rates. This map will be used to separate local from regional uplift and to describe subareas with different tectonic styles that have results from the oblique convergence of the Pacific and Australian plates. Stream-gradient indices describe variations in channel slope and will be used to further examine amounts of recent faulting and to study rates of upstream migration of rapids and waterfalls caused by faulting in streams in with different amounts of power. Terrace tread and strath surfaces will also be evaluated as time lines passing through rapidly deforming landscapes. Stream terraces are common in the valleys of the western United States, but are not as suitable for efficient and complete testing of the tectonic model as the more abundant and extensive New Zealand terraces. Concepts and methods resulting from this study will be applicable to many other tectonically active regions, with different climates, rock erodibility, terrace ages, and streams power. After thorough testing in New Zealand, the proposed model should be used as a new approach to better define areas of high seismic risk in the western United States.