Geomorphic implications of fault zone weakening: Slope instability along the Alpine Fault, South Westland to Fiordland
- 1 June 2004
- journal article
- research article
- Published by Taylor & Francis in New Zealand Journal of Geology and Geophysics
- Vol. 47 (2) , 257-267
- https://doi.org/10.1080/00288306.2004.9515052
Abstract
Tectonic weakening of bedrock along the Alpine Fault Zone (AFZ) in South Westland and northern Fiordland, New Zealand, has favoured erosion of schist‐derived mylonite and cataclasite by a variety of slope failures. This paper describes the basic geomorphic characteristics and effects of chronic and instantaneous slope instability affecting c. 28 km2 in the AFZ, conditioned by groundwater infiltration, geochemical alteration, coseismic hanging‐wall rock fracturing, and gravitational stress in thrust nappes. Mass movement involves 30 complex gully/slip systems and 10 long‐runout landslide deposits, which were identified up‐to‐date, and mainly triggered by fluvial undercutting, increased pore‐water pressures, and possibly, coseismic shaking. Chronic slope instability in gully/slip systems causes rapid delivery of excessive debris to alluvial fans, producing high sediment yields (c. 104 t.km‐2.yr‐1), aggradation, and large‐scale avulsion. The principal hazards from catastrophic landslides at the Westland mountain‐range front are direct physical impact during runout onto the foreland and shortlived blockage of major rivers. Several settlements and infrastructure are located along the range front and are at risk from these geomorphic on‐site and off‐site effects of fault‐related slope instability.Keywords
This publication has 15 references indexed in Scilit:
- Tectonic controls on a large landslide complex: Williams Fork Mountains near Dillon, ColoradoGeomorphology, 2001
- Shattered Rock and Precarious Rock Evidence for Strong Asymmetry in Ground Motions during Thrust FaultingBulletin of the Seismological Society of America, 2001
- Late Quaternary slip rates and slip partitioning on the Alpine Fault, New ZealandPublished by Elsevier ,2001
- The AD 930 long‐runout Round Top debris avalanche, Westland, New ZealandNew Zealand Journal of Geology and Geophysics, 1998
- Erosional control on the structural evolution of a transpressional thrust complex on the Alpine fault, New ZealandJournal of Structural Geology, 1997
- Examination of seismicity in the central Alpine Fault region, South Island, New ZealandNew Zealand Journal of Geology and Geophysics, 1995
- Late Quaternary evolution of the Alpine Fault Zone at Paringa, South Westland, New ZealandNew Zealand Journal of Geology and Geophysics, 1994
- Estimates for the timing of the last coseismic displacement on the Alpine Fault, northern Fiordland, New ZealandNew Zealand Journal of Geology and Geophysics, 1990
- S-C MylonitesJournal of Structural Geology, 1984
- Distribution of large rock avalanche deposits in the central Southern Alps, New ZealandNew Zealand Journal of Geology and Geophysics, 1983