Deep-Seated Bedrock Landslides and Submarine Canyon Evolution in an Active Tectonic Margin: Cook Strait, New Zealand

Abstract

The Cook Strait sector of the Hikurangi subduction margin, off south-east central New Zealand, is dominated by a multi-branched canyon system where landslides are widespread. The objective of this study is to determine the character, origin, and influence of these landslides on the evolution of the canyon system. Multibeam bathymetry covering seven submarine canyons is utilised to characterise landslides' spatial distribution, morphological attributes and area-frequency characteristics. We demonstrate that mass movements within the Cook Strait canyons consist of spatially dense, predominantly retrogressive, small, deep-seated, translational bedrock landslides occurring in Late Cenozoic sequences. These landslides affect up to a quarter of the canyoned area. Concentration of landslides in the shallow canyon reaches (down to 800 m) is attributed to the influence of oceanographic processes originating on the continental shelf such as tidegenerated currents, dense shelf water cascading and internal waves. Canyon incision and wall undercutting, locally favoured by underlying lithological control, are proposed as major landslide drivers in Cook Strait. Ground motion during regional earthquakes is considered a secondary cause. Retrogressive landslides are responsible for canyon widening and wall retreat, cross-sectional asymmetry, preconditioning for additional failure, destabilisation of adjacent slopes and delivery of sediment into canyon floors.

Shallow methane hydrate system controls ongoing, downslope sediment transport in a low‐velocity active submarine landslide complex, Hikurangi Margin, New Zealand

“…Submarine slope instability is widely recognized along the length of the Hikurangi Margin [ Barnes et al ., ; Collot et al ., ; Faure et al ., ; Kukowski et al ., ; Micallef et al ., ; Mountjoy et al ., ; Mountjoy and Micallef , ; Pedley et al ., ]. The continental slope off the coast of Gisborne is subject to widespread mass failure, including some of the largest and best preserved landslide complexes on the margin.…”

Submarine landslides of the Mediterranean Sea: Trigger mechanisms, dynamics, and frequency-magnitude distribution

“…Conversely, on passive margins large sedimentary accumulations tend to build up undisturbed, and, when some minor perturbation occurs (e.g., relatively small earthquake), this sediment is mobilized in large landslides. Frequency-magnitude relationships [Issler et al, 2005;ten Brink et al, 2006, Micallef et al, 2008Chaytor et al, 2009, Behrmann et al, 2014 and more qualitative analysis [e.g., Mcadoo et al, 2000, Krastel et al, 2006Micallef et al, 2012] for other areas worldwide indicate that changes in the frequency-magnitude exponent θ with tectonic setting are global in character.…”

Understanding the potential for tsunami generated by earthquakes on the southern Hikurangi subduction interface

“…Submarine landslides within the Cook Strait canyon system (Mountjoy et al 2009;Micallef et al 2012) are another type of tsunami source with the potential to affect central New Zealand (Mountjoy et al 2014); while they may be earthquake-triggered, such events are not the focus of this paper. We also do not model here the tsunami generation potential of upper plate or outer rise faults in this region (Cousins et al 2009;Power 2013).…”