Quantifying the seismic response of slopes in Christchurch and Wellington : Wellington slope types and characterisation

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SR_2013-058-pdf
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Hancox, G.T.; Perrin, N.D.; Lukovic, B.; Massey, C.I. 2015 Quantifying the seismic response of slopes in Christchurch and Wellington : Wellington slope types and characterisation. Lower Hutt, N.Z.: GNS Science GNS Science report 2013/58 40 p. + appendices

Abstract: This report presents the results of studies to develop a classification of the main slope types in the Wellington urban area extending from the Hutt Road south of Petone to Owhiro Bay. The aim of the slope classification is to provide a basis for quantifying the effects that slope geometry, geology (contrasting materials and parameters) and earthquake source have on amplifying ground shaking and potential triggering of landslides during earthquakes. Slope profiles were generated at 57 sites using a LiDAR-based digital elevation model with 1 m resolution (cell size) and vertical accuracy of ± 0.5 m, which was used to generate 5 m contours, and hillshaded and slope angle models. The slope profiles were used along with GIS generated hillshaded and slope maps, aerial photos, GoogleEarth images, and existing historical information on slope performance to compile a range of slope attributes, including: slope height; slope angle (minimum, maximum, overall, and significant variations and oversteepening of local slope gradient, e.g., cut slope batters); slope type (natural, valley, coastal, and fault scarps); engineered slopes (cuts and fills); and past slope failures (prehistoric and historic landslides). The relationships of slope height to overall slope angle were analysed for the 57 slope profiles, and a number of slope classes were established for the Wellington area, as follows: 1. Natural slopes: (a) Valley slopes; (b) Wellington Fault scarp slopes; (c) Coastal slopes; (d) Slopes with large pre-existing landslides. 2. Engineered slopes: (a) Cuts for roads, railway lines, and urban developments; (b) Cut slopes in quarries; (c) Fill slopes. (auth)