Suggestions for monitoring deformation on the Wellington fault and in the Wellington region (with discussion on earthquake prediction)

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Lensen, G.J. 1968 Suggestions for monitoring deformation on the Wellington fault and in the Wellington region (with discussion on earthquake prediction). Lower Hutt: New Zealand Geological Survey. Report NZGS 28 39 p.

Abstract: Horizontal and vertical deformation is shown to occur continuously on a regional basis, both between and at times of major earthquakes. Overseas evidence shows that such continuous deformation can be measured. The pattern, the amount and the rate of such deformation change as the time of a major earthquake approaches. Particularly clear discernible deformation can precede a major earthquake by months or days. Irreversible deformation, commonly though not exclusively faulting, is a usual phenomenon when the major earthquake occurs. Concerted efforts are being made overseas to collect deformational data of many kinds with the ultimate aim of earthquake prediction. In New Zealand the only work is the recent installation of about 20 marker patterns across active faults, to be surveyed at regular intervals. Repeated precise levellings at Waiotapu demonstrate that continuous deformation also occurs in New Zealand. These efforts are very small in comparison with those ultimately required to predict major earthquakes through deformation studies. Major active faults are likely to move at times of major earthquakes in the Wellington region. As the amount and rate of continuous deformation between faultings are expected to be measurable, a series of proposals to monitor the Wellington region is put forward. The proposals are designed to measure periodically horizontal deformation by triangulation, trilateration and azimuth checks, and vertical deformation by precise levelling. Such deformation can also be monitored continuously through tilt and strain meters and tide gauges. A series of progressively wider studies of areal deformation can be undertaken. These studies are complementary rather than supplementary to each other and a failure to undertake particular studies wouldeave serious gaps in knowledge, making those studies that were undertaken more difficult to interpret. Frequencies of implementation of proposals are given, and tentative costs assessed. The proposals will lead to estimation of the nature and magnitude of deformation that may need to be taken into account in civil engineering. Their usefulness for earthquake prediction is not certain, but without adequate data such prediction will not be possible.