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Active Landslides in Gisborne, New Zealand: InSAR Monitoring and Toxic Minerals Exposed in Scarps
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 6th Asia Pacific Meeting on Near Surface Geoscience and Engineering, May 2024, Volume 2024, p.1 - 5
Abstract
Summary
Landslides are widespread geomorphological features on New Zealand’s North Island. This study focuses on the steep slopes in Gisborne, a city located on the northeast coast of the North Island, at the Hikurangi subduction margin. The region is affected by a range of geological hazards, including earthquakes, tsunami, mud volcanoes, and landslides. The latter are most often initiated by rainstorms, and recently Gisborne has been subject to a succession of damaging rainfall-triggered landslide events, initiated by extra-tropical cyclones, and slow-moving “atmospheric rivers”. The terrain consists of young, weak, sedimentary rocks and soils, and these fail via slumps, transitioning downslope into more mobile flows. Interferometric synthetic aperture radar (InSAR) indicates slope movements of ∼70 mm/year, above roads and houses. Seasonal changes, due to shrinking and swelling of expansive soils are also apparent from InSAR. Remote sensing has been augmented by intrusive investigations and laboratory testing of surface materials. In fresh scarps formed by landslides, the naturally-occurring zeolite mineral, erionite, has been identified. When inhaled, erionite mineral fibers are typically more carcinogenic than asbestos fibers. Hence, the presence of erionite, exposed in newly-formed landslide scarps, is an additional emerging geological hazard in Gisborne that has hitherto gone unreported, and may require mitigation.
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