Marine Geohazard along the Hikurangi Margin, New Zealand
Intervenant : Geoffroy Lamarche
National Institute of Water and Atmospheric (NIWA) Research, Wellington
University of Auckland, Auckland
New Zealand straddles the Pacific-Australia convergent plate boundary and the associated >250 kmwide deformation zone of the Hikurangi Margin. The subduction interface along the margin is New Zealand’s largest earthquake hazard, closely followed by the Alpine Fault, submarine volcanic activity and massive submarine debris avalanches. The region has very short historical earthquake and tsunami records, and there is no record of a rupture of the Hikurangi subduction plate interface. Turbidite paleoseismology approaches provide a means to develop robust long-term (>10,000 yrs) earthquake records and to potentially recognise the occurrence of such mega-events. Two of the most damaging earthquakes in New Zealand history have occurred since 2010! The 4 Sep 2010 Mw7.1 Christchurch and 14 Nov 2016 Mw 7.8 Kaikoura earthquakes. The latter is unique in many aspects and is the second largest in NZ history, only surpassed by the Mw8.2 Wairarapa earthquake. Following the Nov. 2016 earthquake, we were a ble to map the impact of the event on the seafloor, including the formation of a turbidites that was samples 700 km away from the epicentre.