Towards a record of Holocene tsunami and storms for northern Hawke's Bay, New Zealand

Abstract

Eleven sand layers occur within Holocene lowenergy estuarine and marginal marine sequences of blue-grey silty clay at two sites on the coastal plain between Wairoa and Mahia Peninsula, northern Hawke's Bay, New Zealand. The sedimentology and fossil assemblages of these layers are consistent with deposition by high-energy influxes to the sites. Three influxes are terrestrial in nature and are thought to represent alluvial flood events. All other sand layers are marine derived and are likely to be the result of storm surges or tsunami. Tsunami inundation is favoured for two sand layers that occur in association with evidence for sudden subsidence at c. 6300 and c. 4800 yr BP The c. 6300 yr inundation also coincides with previously identified evidence for a tsunami at a site 10 km westwards along the coast. Further investigation is required to distinguish between tsunami and storm surge deposition for the remaining six layers.

Estimation of Tsunami Hazard in New Zealand due to South American Earthquakes

“…), many of which were documented by early European missionaries, but it is difficult to attach specific dates to these events and to establish whether or not particular stories relate to the same event. Paleo-tsunami studies (for example, COCHRAN et al, 2005;GOFF et al, 2000;NICHOL et al, 2003) have identified a number of large tsunami inundation events in the pre-historical period, but their sources are not always clear. What is clear is that New Zealand has a significant tsunami hazard problem that the shortness of the historical record may not adequately represent.…”

Evaluating the coastal deformation mechanisms of the Raukumara Peninsula, northern Hikurangi subduction margin, New Zealand and insights into forearc uplift processes

“…Intermittent subsidence of the Te PaeroaÁOpoho coastal wetlands (Fig. 3A) is supported by microfossil evidence of two sudden subsidence event horizons that are overlain by palaeotsunami deposits; the events are dated at c. 7100 and 5550 a BP (Cochran et al 2005. At Opoutama and Whangawehi Stream, there are insufficient data to define the deformation mechanism.…”

“…Nelson et al 1996;Clague 1997), Chile (Cisternas et al 2005), central Hawke's Bay and Bay of Plenty, New Zealand (Hayward et al 2004Cochran et al 2005Cochran et al , 2006, we define two further characteristics of intermittent, coseismic coastal deformation that are typically related to subsidence: microfossil evidence of sudden palaeoenvironmental change and the presence of associated palaeotsunami deposits (Table 1). The methodology of using microfossils for relative sea-level studies is well-established and micropalaeontological detection of coastal earthquakes has also been used at several locations in New Zealand (e.g.…”

Tsunami Forecasting and Monitoring in New Zealand

“…Paleotsunami studies (e.g. COCHRAN et al, 2005;GOFF et al, 2000;NICHOL et al, 2003) have also identified a number of large inundation events in the pre-historic period. In the case of both oral history and paleotsunami analysis it is often difficult to determine either a precise date or source.…”