Structure, late Quaternary slip rate and earthquake potential of marine reverse faults along the North Westland deformation front, New Zealand

Abstract

The North Westland deformation front runs offshore for 320 km between Cape Farewell and Hokitika at a distance of 3-30 km from the coast. From marine seismic reflection profiles integrated with published sediment core and coastal uplift data, we infer late Quaternary activity on six major reverse faults. The principal structures are the Cape Foulwind, Kahurangi and Kongahu faults and the newly named Farewell, Elizabeth and Razorback faults. They include Late Cretaceous and Paleogene rift faults that were reactivated as reverse faults during the late Cenozoic. Best estimates of late Quaternary (<120 ka) slip rates for different faults range from 0.05-0.75 mm a -1 . Nine potential earthquake sources are identified, including four segments of the Cape Foulwind Fault. They are of length c. 20-120 km, are potentially capable of producing moderate-to large-magnitude earthquakes of M w 6.7-7.8 and represent a seismic risk to coastal communities. Best estimates of recurrence intervals for individual fault sources range from about 7600 years to 30,400 years, with large uncertainties in slip rates of up to -0.4, +1.0 mm a -1 reflected by the wide range of recurrence intervals. ARTICLE HISTORY

Novel Application of a Compound-Specific Stable Isotope (CSSI) Tracking Technique Demonstrates Connectivity Between Terrestrial and Deep-Sea Ecosystems via Submarine Canyons

“…With respect to similar tectonic events on the Alpine Fault or other faults in the proximity of the Hokitika Canyon, it is anticipated that potentially more substantial and catastrophic episodes are likely to occur in this canyon and others on the west coast of South Island, especially given the level of groundshaking expected with a future rupture scenario on the Alpine Fault (Sutherland et al, 2007;Howarth et al, 2018). The reverse Cape Foulwind Fault extends across the shelf east of the Hokitika Canyon head and parallel to the coast and may also be capable of generating sizeable earthquakes (M W 7.5) with large single event displacements (∼5 m) ( Barnes and Ghisetti, 2016). Therefore, while presently high accumulation and transport of terrestrial organic matter appears to occur down the length of Hokitika Canyon, and potentially the other canyons along the west coast of South Island (Mitchell et al, 2012), random or episodic tectonic events may also be a factor in the long term transfer of organic carbon to the deep ocean in this region.…”

Introduction toNZJGGspecial issue in honour of John Beavan's scientific contributions

“…These include the first-ever measurements of the vertical uplift rate of the southern Alps (Beavan et al 2010b), the first GPS estimates of slip rates and interseismic coupling across the Alpine Fault system (Beavan et al 1999) and detailed investigations of the Dusky Sound earthquake sequence (Beavan et al 2011a) and other broader South Island problems Wallace et al 2007). Further contributions to the understanding of crustal deformation in the northwestern South Island have been made by Barnes & Ghisetti (2016). Seismic reflection data have been used to characterise six major active reverse faults of the North Westland deformation front that extends for 320 km offshore between Cape Farewell and Hokitika.…”