Alluvial fan response to Alpine Fault earthquakes on the Westland piedmont, Whataroa, Aotearoa-New Zealand

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dc.contributor.authorAlmond, Peter C.
dc.contributor.authorBerryman, Kelvin
dc.contributor.authorVillamor, Pilar
dc.contributor.authorRead, Stuart
dc.contributor.authorAlloway, Brent A.
dc.contributor.authorTonkin, Philip
dc.date.accessioned2025-01-20T20:15:16Z
dc.date.available2025-01-20T20:15:16Z
dc.date.issued2023
dc.description.abstractWe examined the stratigraphy of alluvial fans formed at the steep range front of the Southern Alps at Te Taho, on the north bank of the Whataroa River in central West Coast, South Island, New Zealand. The range front coincides with the Alpine Fault, an Australian-Pacific plate boundary fault, which produces regular earthquakes. Our study of range front fans revealed aggradation at 100- to 300-year intervals. Radiocarbon ages and soil residence times (SRTs) estimated by a quantitative profile development index allowed us to elucidate the characteristics of four episodes of aggradation since 1000 CE. We postulate a repeating mode of fan behaviour (fan response cycle [FRC]) linked to earthquake cycles via earthquake-triggered landslides. FRCs are characterised by short response time (aggradation followed by incision) and a long phase when channels are entrenched and fan surfaces are stable (persistence time). Currently, the Te Taho and Whataroa River fans are in the latter phase. The four episodes of fan building we determined from an OxCal sequence model correlate to Alpine Fault earthquakes (or other subsidiary events) and support prior landscape evolution studies indicating >= M7.5 earthquakes as the main driver of episodic sedimentation. Our findings are consistent with other historic non-earthquake events on the West Coast but indicate faster responses than other earthquake sites in New Zealand and elsewhere where rainfall and stream gradients (the basis for stream power) are lower. Judging from the thickness of fan deposits and the short response times, we conclude that pastoral farming (current land-use) on the fans and probably across much of the Whataroa River fan would be impossible for several decades after a major earthquake. The sustainability of regional tourism and agriculture is at risk, more so because of the vulnerability of the single through road in the region (State Highway 6).
dc.description.funderGNS Science
dc.fuente.origenWOS
dc.identifier.doi10.1002/esp.5589
dc.identifier.eissn1096-9837
dc.identifier.issn0197-9337
dc.identifier.urihttps://doi.org/10.1002/esp.5589
dc.identifier.urihttps://repositorio.uc.cl/handle/11534/92250
dc.identifier.wosidWOS:000975016700001
dc.issue.numero9
dc.language.isoen
dc.pagina.final1829
dc.pagina.inicio1804
dc.revistaEarth surface processes and landforms
dc.rightsacceso restringido
dc.subjectaggradation
dc.subjectaggradation and flooding hazard
dc.subjectalluvial fans
dc.subjectAlpine Fault earthquakes
dc.subjectearthquake-triggered landslides
dc.subjectlandscape response
dc.subject.ods13 Climate Action
dc.subject.odspa13 Acción por el clima
dc.titleAlluvial fan response to Alpine Fault earthquakes on the Westland piedmont, Whataroa, Aotearoa-New Zealand
dc.typeartículo
dc.volumen48
sipa.indexWOS
sipa.trazabilidadWOS;2025-01-12
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