11:45 AM - 12:00 PM
[HCG35-10] Palaeoseismic signals in coastal dune ridge systems
Keywords:Earthquakes, Tsunamis, Dune ridges, Landslides, Rivers, Geomorphology
First, a well dated suite of coastal dune ridge sequences in SW New Zealand are shown to be linked by a series of geomorphological processes to large ruptures of the regionally significant Alpine fault (Wells and Goff, 2006; 2007). These fine resolution chronological sequences were achieved using the ages of trees from the ancient forest still growing there. A time lag of 10-50 years between earthquake and dune ridge formation attests to the short sediment transport distance from the mountains to the coast (~50 km) coupled with high annual rainfall. Second, these data are contrasted with evidence from SE New Zealand where a longer sediment transport distance from the mountains to the coast (~150 km) coupled with lower annual rainfall causes a time lag of 150-200 years between earthquake and dune ridge formation (McFadgen and Goff, 2005). Differences in coastal configuration and a lack of native forest chronology complicate event chronologies but additional geomorphological indicators and human responses enhance interpretations. Third, we investigate beach ridges of northern Honshu with a focus on the Sendai Plain where a study carried out following the 2011 Tohoku-oki earthquake and tsunami reveal a regional picture of the seismic driving of beach ridge formation. More work needs to be done but the initial results are both exciting and have significant implications for understand the palaeoseismic and palaeotsunami record for the region.
Goff, J. and McFadgen, B.G. (2002) Seismic driving of nationwide changes in geomorphology and prehistoric settlement ? a 15th Century New Zealand example. Quaternary Science Reviews, 21, 2229-2236.
Goff, J. and Sugawara, D. (2014) Seismic driving of sand beach ridge formation in northern Honshu? Japan. Marine Geology, 358, 138-149.
McFadgen, B.G. and Goff, J. (2005) An earth systems approach to understanding the tectonic and cultural landscapes of linked marine embayments: Avon-Heathcote Estuary (Ihutai) and Lake Ellesmere (Waihora), New Zealand. Journal of Quaternary Science, 20, 227-237.
Wells, A. and Goff, J. (2007) Coastal dunes in Westland, New Zealand, provide a record of paleoseismic activity on the Alpine fault. Geology, 35, 731-734.
Wells, A. and Goff, J. (2006) Coastal dune ridge systems as chronological markers of paleoseismic activity ? a 650 year record from southwest New Zealand. The Holocene, 16, 543-550.
Figure 1: The seismic cascade of physical and human environmental responses to giant earthquakes (after Goff and McFadgen, 2002; Goff and Sugawara, 2014).