Kaikoura Peninsula Research Articles

Contribution from Multiple Fault Ruptures to Tsunami Generation During the 2016 Kaikoura Earthquake

The 2016 Kaikoura, New Zealand, earthquake was one of the most complex ruptures ever recorded. The epicentre was located well inland, but the rupture area extended offshore and generated a modest tsunami which was recorded by tide gauges. Here, we present a detailed estimate of seafloor vertical displacement during the earthquake sequence by a joint inversion of tsunami waveforms and vertical displacement data observed at GPS stations and obtained by field surveys. The combined dataset provides a solution with good resolution, capable of resolving test sources of 20 km of characteristic diameter throughout the study area. We found two seafloor uplift regions which are located very close to the coast, one is located offshore of the Kaikoura peninsula and the other larger uplift region is located near the Kekerengu and Needles faults. To estimate crustal deformation with a complete spatial coverage of the event, the estimated seafloor vertical displacement was combined with the inland vertical displacement from InSAR and GPS datasets. This vertical displacement is then inverted for the fault slip distributions of the Needles, Jordan–Kekerengu, Papatea, Hundalee, Hump faults, and a newly identified fault beneath Kaikoura. We also found that the Needles fault is probably an offshore extension of the Kekerengu fault. The seismic moment calculated from the fault slip distributions by assuming a rigidity of 2.7 × 1010 N/m2, is 5.19 × 1020 Nm or equivalent to Mw 7.8. This total seismic moment estimate is consistent with that of the Global Centroid Moment Tensor solution. The tsunami potential energy calculated from the seafloor vertical displacement is 9.40 × 1012 J, of which about 70% is attributed to movement on the faults known to have ruptured, suggesting a secondary source for tsunami generation.

Distribution and abundance of Hector's dolphins (Cephalorhynchus hectori) off Kaikoura, New Zealand

Boat-based surveys of Hector's dolphins (Cephalorhynchus hectori) were conducted throughout 2013 to evaluate their distribution and abundance off Kaikoura. We conducted a total of 48 surveys and encountered 164 groups of Hector's dolphins. This study showed that Hector's dolphins off Kaikoura preferred areas of shallow, nearshore waters with poor water clarity and that there were more sightings to the north of the Kaikoura Peninsula than to the south. Using photo-identification techniques we identified 47 distinct individuals within the study area and these known individuals were only sighted either north or south of the Kaikoura Canyon. This study, combined with opportunistic sightings data collected from 2005–2013, improves our understanding of habitat use within the Kaikoura area by Hector's dolphins. These data suggest that the canyon area, characterised by very deep waters, could act as a natural barrier dividing the Hector's dolphins off Kaikoura into two separate groups.

Surveillance for arboviral zoonoses in New Zealand birds

Given the significant burden that emerging infectious diseases place on global economies and public health, the monitoring and mitigation of, and early response to, potential infectious diseases are of the highest priority. The objective of this study was to survey for known and other potential arboviral zoonoses in multiple bird species at four locations in New Zealand. Common bird species were targeted for blood sampling during two southern hemisphere summers. Sera from each period (n=185 and n=693) were screened in an epitope blocking enzyme immunoassay for flavivirus antibody detection. In the first season, testing for antibodies to specific alphaviruses was conducted on samples with sufficient sera (n=22). In the second season, blood clots (n=544) were screened for viral presence by polymerase chain reaction (PCR) for alphaviral and flaviviral RNA, and virus isolation (n=146) was conducted. Flavivirus antibodies were detected in 13 species, and one Australasian gannet (Morus serrator) from one site was positive for antibodies to Ross River virus. PCR tests and virus isolation were all negative. Evidence for flavivirus exposure in seabirds at Kaikoura Peninsula and Cape Kidnappers suggests that viruses isolated from seabirds and associated ticks in New Zealand in the late 1970s are still present. Evidence for flavivirus exposure in passerines at Kaikoura Peninsula, Cape Kidnappers and Mokoia Island is novel. The Ross River virus finding is also new and supports the hypothesis that migratory seabirds are an import pathway for such agents into New Zealand.

Long term shore platform surface lowering rates: Revisiting Gill and Lang after 32 years

In 1978 E.D. Gill and J.G. Lang installed 53 micro-erosion meter (MEM) sites on shore platforms along the Otway coast in south eastern Australia. Surface lowering rates were originally determined from 2yr of measurements (1979 and 1980) and showed that the mean annual rate of lowering from all sites was 0.37mm/yr−1. We re-measured these MEM sites 32yr after the first set of readings were taken in February 1979. We relocated 49 of the original 53 bolt sites and were able to measure 45 of them. From the sites we measured, the mean annual rate of shore platform lowering was 0.31mm/yr−1. Rates of surface lowering on shore platforms are commonly reported from studies of only two or three years and only one other record exceeds 30yr (Kaikoura Peninsula, NZ; 1.09mm/yr−1), in that case fewer than half of the original bolt sites were functioning because erosion had removed bolts. Along the Otway coast rates of erosion are much slower hence the greater number of still readable sites after 32yr. Compared to other micro-erosion meter studies the rates reported here are at the lower end of the range of values from around the world but nevertheless consistent with rates from the Otway Coast and others in similar lithology. We found no statistical difference between erosion rates calculated over 2yr (1979 to 1980) and 32 (1979 to 2011) years supporting the view that shore platform lowering rates measured over 2yr are representative of decadal scales.

Plasmodium infections of red-billed gulls (Larus scopulinus) show associations with host condition but not reproductive performance

High prevalence of Plasmodium infection in some non-native bird species in New Zealand, coupled with distributional expansion of the introduced mosquito vector Culex quinquefasciatus, has raised concerns that immunologically naïve native species might be increasingly at risk from malarial parasites. We combined polymerase chain reaction (PCR) screening of archived blood samples with long-term field data of red-billed gulls (Larus scopulinus) at Kaikoura Peninsula to estimate the prevalence of malarial infection and its effect upon host condition and breeding success. Plasmodium prevalence assessed with PCR was 7.8±3.4%, 10-fold greater than estimates from microscopic analysis of blood smears (c. 0.7%, Tompkins et al. 2010). Phylogenetic analysis of parasite cytochrome b sequences isolated from red-billed gulls indicates that lineage RBG1 falls within a clade containing P. cathemerium morphospecies, whereas RBG2, isolated from a single individual, clusters with P. elongatum. We show that red-billed gulls infected with Plasmodium have bred at Kaikoura dating back to at least 1992, that chronic infections of lineage RBG1 are maintained over several years in some individuals, and that infection is associated with decreased body condition in breeding individuals of both sexes. There is currently no evidence that Plasmodium infection is associated with reduced breeding performance. However, further study involving the ecological context and temporal dynamics of infection is needed to assess cumulative effects on lifetime reproductive success.

The morphodynamics of shore platforms in a micro-tidal setting: Interactions between waves and morphology

The interactions between waves and morphology on shore platforms were investigated at four platforms located at Kaikoura Peninsula, New Zealand and the Otway coast, Victoria, Australia. Waves were measured over six tidal peaks of a spring tidal sequence at each site during a six month period (February 2007 – July 2007). This paper reports the results of an investigation into the research question: how are waves modified by platform morphology in a micro-tidal setting? Through the investigation of wave interactions on shore platforms it was found that complex hydrodynamic patterns formed on the shore platforms studied. Through direct measurement of waves on the platforms it was found that wave attenuation was not dependent on platform width, but rather influenced by platform gradient and depth of water on the platform. Spectral analysis was used to assess how wave energy was transformed across the platforms. At three of the four platforms investigated, energy gradients formed across the platform with wave energy recorded within the infragravity range.

Carbonate sediments in a cool-water macroalgal environment, Kaikoura, New Zealand

Brown and red, and to a lesser extent green, macroalgae are a hallmark of intertidal rocky coasts and adjacent shallow marine environments swept by stormy seas in middle and high latitudes. Such environments produce carbonate sediment but the sediment factory is neither well-documented nor well-understood. This study documents the general marine biology and sedimentology of rocky coastal substrates around Kaikoura Peninsula, a setting that typifies many similar cold-temperate environments with turbid waters and somewhat elevated trophic resources along the eastern coast of South Island, New Zealand. The macroalgal community extends down to 20 m and generally comprises a phaeophyte canopy beneath which is a prolific rhodophyte community and numerous sessile calcareous invertebrates on rocky substrates. The modern biota is strongly depth zoned and controlled by bottom morphology, variable light penetration, hydrodynamic energy and substrate. Most calcareous organisms live on the lithic substrates beneath macroalgae or on algal holdfasts with only a few growing on macroalgal fronds. A live biota of coralline red algae [geniculate, encrusting and nodular (rhodoliths)], bryozoans, barnacles and molluscs (gastropods and epifaunal bivalves), together with spirorbid and serpulid worms, small benthonic foraminifera and echinoids produce sediments that are mixed with terrigenous clastic particles in this overall siliciclastic depositional system. The resultant sediments within macroalgal rocky substrates at Kaikoura contain bioclasts typified by molluscs, corallines and rhodoliths, barnacles and other calcareous invertebrates. In the geological record, however, the occurrence of macroalgal produced sediments is restricted to unconformity-related early transgressive systems tract stratigraphic intervals and temporally constrained to a Cenozoic age owing to the timing of the evolution of large brown macroalgae.

Analysis of relationships between micro-topography and short- and long-term erosion rates on shore platforms at Kaikoura Peninsula, South Island, New Zealand

Using long-term data sets of erosion rates for the shore platform at Kaikoura it is possible to assess the relationships between erosion rates over two and ten years. Erosion rates do not tend to vary significantly between the two measurement periods. Using linear regression analysis a difference in the nature of topographic change is identified between mudstone and limestone shore platforms. The mudstone platforms show a consistent mode of topographic change, parallel retreat or smoothing, between the short and long terms. Limestone shore platforms show no consistent mode of topographic change. It is suggested that the consistent behaviour of the mudstone platforms occurs because the mudstone surface is responding as a single unit at this scale of measurement. Erosion rates tend to increase with distance from the seaward edge of the platforms and this may reflect the increasing significance of wetting and drying cycles, as well as the increasing mix of erosional processes as sub-aerial processes increase in importance. This changing mix of erosional processes may also explain the variations in gradient coefficients between short- and long-term erosion rates with distance from the seaward edge of the platforms.

The impact of climate fluctuation on food availability and reproductive performance of the planktivorous red‐billed gullLarus novaehollandiae scopulinus

1. Using 41 years of data, we examined annual variations in the reproductive performance of the red-billed gull at the Kaikoura Peninsula, New Zealand and related these to changes in climate, oceanography and the availability of the planktonic euphausiid Nyctiphanes australis, the bird's principal food. 2. In 1994 the population began to decline, and between 1983 and 2003 it was reduced by 51%. Adult non-breeders comprised an average of 32% of the population between 1983 and 1994, but following the decline they averaged only 18%. The age at recruitment changed markedly following the population decline: 27% of 2-year-old males bred for the first time prior to the decline, whereas the corresponding figure after the decline was 38%. The proportion of females commencing to breed as a 3-year-old was not significantly different before or after the decline. 3. An increase in the availability of euphausiids increased the likelihood of breeding and the recruitment of young individuals, caused earlier laying and resulted in an increase in the condition of adults, egg volume of gulls laying two egg clutches, clutch size and fledging success. 4. The relationship between food availability and the number of pairs that bred, laying date, clutch size and fledging success was significantly different prior to and after the population decline. The underlying cause appears to be a compensatory density-dependent mechanism that reduced interspecific competition for food. 5. The relative abundance of N. australis was correlated positively with the Southern Oscillation Index (SOI) and the frequency of occurrence of NE winds. The proportion of non-breeders and mean laying date were correlated negatively with the SOI, and mean egg volume of two egg clutches correlated positively with the SOI. 6. These results emphasize that availability of adult euphausiids is critical for red-billed gulls. We hypothesize that high primary productivity of inshore water near Kaikoura in winter, linked to a stable water column of coastal water and upwelling of additional dissolved inorganic nutrients, increases the availability of adult euphausiids to the red-billed gull as long as the coastal water is not replaced by offshore subtropical water intrusions of warmer, low-nutrient water.

The Role and Presence of a Guide: Preliminary Findings from Swim with Seal Programs and Land-Based Seal Viewing in New Zealand

Marine mammal tourism is increasing worldwide and pinnipeds are increasingly a target of guided tourism ventures, in the form of "walk" and "swim-with" seal programs. This article aimed to quantify the response of seals to commercial seal swim operations and guided walks; compare responses of seals to guided versus unguided tours; and determine what human behaviors were more likely to elicit an avoidance response from the seals. Both guided and unguided commercial seal swims, as well as freedom/independent swims were monitored in Abel Tasman National Park, and Kaikoura, located in the South Island of New Zealand in the 2000/2001 austral summer. The behaviors of seals approached during seal swims were monitored from kayak or land-based platforms. Seal behavior in response to a guided walk on the Kaikoura Peninsula was also monitored; landing is not permitted on Tonga Island so land-based approaches were not observed there. Commercial seal swims elicited fewer avoidance responses than independent swimmers; however, no significant differences were found between seal swim companies. The benefit of having a guide present on walks to view seals was considerable, with 15% fewer seals responding ("changing behavior" or "avoiding") to tourists on guided walks than independent land-based tourist approaches. Key factors that influence seal responses to tourist approaches include group size: seals responded significantly more to groups of seven to nine tourists than to tour groups of smaller size. The findings presented in this study highlight some key factors that influence seal responses to tourist approaches, and also show that the presence of a guide significantly reduces the amount of avoidance responses from seals. As the popularity of seal tours increases, this information will be useful in establishing guidelines to effectively manage encounters with positive outcomes for both animals and tourists.

The influence of seasonal and local weather conditions on rock surface changes on the shore platform at Kaikoura Peninsula, South Island, New Zealand

A traversing micro-erosion meter (TMEM) was used to measure micro-scale surface changes in a 45 cm 2 area of an intertidal mudstone shore platform on Kaikoura Peninsula, New Zealand, with hourly readings taken over 5 days for two seasons, within 4 h either side of low tide. For all monitoring events, the relative height of a total of 120 co-ordinates were obtained, resulting in 4200 and 4800 measurements for the summer and winter seasons respectively. Within seasons, samples were grouped according to the presence of rain or no rain. Significant changes were found in the micro-topography with variations in temperature and among rain and no rain sample groups. For both seasons, in the absence of rain, there were positive linear relationships between rock surface temperatures and rock surface elevations, and regression analysis explained 42.3% and 46.5% of this variation for the summer ( y = 0.098 + 0.004 x; p-value = 0.007) and winter ( y = 0.007 + 0.012 x; p-value < 0.001) seasons respectively. It is suggested that incorporating weather readings alongside measurements of surface change could not only improve extrapolations of shore platform erosion from short-term studies, but also differentiate fluctuations in rock surfaces due to changes in rock surface temperatures from other processes involved in shore platform erosion.

Interpretation of erosion rates on rock surfaces

Simple linear regression is used to interpret erosion rates on two shore platforms from the Kaikoura Peninsula, South Island, New Zealand. Using this analysis it is suggested that measured rates could be viewed as representatives of populations of erosion rates moving about a changing fitness landscape. The potential of such a view for understanding erosion rates is outlined.

Statistical analysis of the significance of site topography and erosion history on erosion rates on intertidal shore platforms, Kaikoura Peninsula, South Island, New Zealand

Sites with five periods of consecutive measurements from the Kaikoura Peninsula data were used to assess the influence of erosional history and surface topography upon subsequent erosion rates. Analysis of multilevel models suggests that initial erosion rates and initial surface topography have a significant, but decreasing influence upon subsequent erosion rates. Surface topography and erosion rates immediately prior to each measurement period have a consistent positive and negative relationship respectively to erosion rates in the subsequent measurement periods. These data suggest that there is a short-term memory influencing erosion rates at any specific measurement period. Use of traversing microerosion meter data may, however, not be the most appropriate means of analysing the causes of the variance of erosion at the intra-site scale.

Sediment on rocky intertidal reefs: Effects on early post-settlement stages of habitat-forming seaweeds

Modification of the coastal environment by human activities often leads to an increase in sedimentation of nearshore waters, with potential impacts on benthic marine assemblages. Here we assess the relationships between the levels of sedimentation, wave exposure and benthic organisms on rocky intertidal platforms around the Kaikoura Peninsula in southern New Zealand. We designed and tested five sediment traps to provide a tool for measuring the relative abundance of sediment across sites. Using field- and laboratory-based experiments, we tested hypotheses concerning whether different levels of sedimentation affected algal germling survival and algal zygote attachment, and whether the interactions of grazers and sediments affected germling survival. Levels of sediment and exposure were inversely related across seven sites. The fucoid alga Hormosira banksii characterized the more sedimented wave-sheltered and intermediately wave-exposed sites, with up to 80% cover in the lower mid-tidal zone, while the bull kelp Durvillaea antarctica characterized the three most wave-exposed sites. Grazing molluscs were found across all sites but species abundances varied by sediment and exposure levels. We did two 11-day trials testing the effects of different levels of sediment and different species of molluscan grazers on the survival of 1-week-old Hormosira germlings. Generally, there was no significant treatment effect of grazers, but mortality varied considerably among sites. In particular, one site had very high levels of sediment, which resulted in 100% mortality of germlings across all grazer treatments. Removing sediment at 1-week, 2-week and 4-week intervals made no difference to the survival of Hormosira germlings. In laboratory-based experiments, a light dusting of sediment reduced the percentage of zygotes of Hormosira by 34% and Durvillaea by 71% that attached to primary substratum, and a complete cover of sediment prevented attachment altogether. Overall, the effects of sediments and its interaction with molluscan grazing were highly variable but often large, particularly on the attachment of zygotes to primary substratum.

Short‐term microscale topographic changes of coastal bedrock on shore platforms

AbstractWe report a series of short‐term (diurnal) rock surface monitoring studies on inter‐ and supra‐tidal shore platforms using a traversing micro‐erosion meter at two sites, Kaikoura Peninsula, New Zealand, and Apollo Bay, Victoria, Australia. Statistically significant day‐to‐day changes were measured. Surface rise and lowering occurred at rates above instrument error, with a maximum range of 3·378 mm between 1·697 mm (lowering) and ‐1·681 mm (rise). Individual measurements showed rises greater than 2 mm. These daily variations reveal that surface lowering and rise occur at a much shorter time scale than previously reported from other studies. The patterns observed suggest wetting and drying is the most likely process causing surface changes at these temporal scales. We argue that traversing micro‐erosion meter studies operating at a short‐term time scale of day‐to‐day provide meaningful results that open new opportunities for studying rock weathering and erosion in a coastal environment. Copyright © 2004 John Wiley &amp; Sons, Ltd.

Echolocation signals of dusky dolphins (Lagenorhynchus obscurus) in Kaikoura, New Zealand.

An array of four hydrophones arranged in a symmetrical star configuration was used to measure the echolocation signals of the dusky dolphin (Lagenorhynchus obscurus) near the Kaikoura Peninsula, New Zealand. Most of the echolocation signals had bi-modal frequency spectra with a low-frequency peak between 40 and 50 kHz and a high-frequency peak between 80 and 110 kHz. The low-frequency peak was dominant when the source level was low and the high frequency peak dominated when the source level was high. The center frequencies in the dusky broadband echolocation signals are among the highest of dolphins measured in the field. Peak-to-peak source levels as high as 210 dB re 1 microPa were measured, although the average was much lower in value. The levels of the echolocation signals are about 9-12 dB lower than for the larger white-beaked dolphin (Lagenorhynchus albirostris) which belongs to the same genus but is over twice as heavy as the dusky dolphins. The source level varied in amplitude approximately as a function of the one-way transmission loss for signals traveling from the animals to the array. The wave form and spectrum of the echolocation signals were similar to those of other dolphins measured in the field.

The use of multilevel modeling in evaluating controls on erosion rates on inter-tidal shore platforms, Kaikoura Peninsula, South Island, New Zealand

Repeated measurements of erosion rates on seashore platforms on Kaikoura Peninsula, South Island, New Zealand were gathered over a 28-month period using a micro-erosion meter (MEM). The resultant hierarchical dataset was analysed using multilevel regression modeling. Results indicate that there is persistent variation of rates across measurement occasions within individual points and significant variation is also found across sites (or local ‘contexts’). There is little evidence for significant variation across individual points. The explanatory variables of platform/rock type, distance along platform and seasonality all have a significant effect on the erosion rates and aid the explanation of some of the variation in erosion rates across sites.

Surface swelling of coastal bedrock on inter-tidal shore platforms, Kaikoura Peninsula, South Island, New Zealand

This paper reports the occurrence of swelling of coastal bedrock measured with a traversing micro-erosion meter (TMEM) on inter-tidal mudstone and limestone shore platforms. While numerous micro-erosion meter (MEM) studies have been made, only a small number have reported surface swelling. During this study, 24,055 measurements were made with a TMEM, of those 4047 indicated swelling or 17% of the total number of measurements. Vertical swelling of up to 8.9 mm was measured and values of 3 and 4 mm were common. Swelling displayed a complex pattern with minor swelling being superimposed on longer period episodes. Duration of swelling events in excess of 697 days were recorded, while other events were commonly in the order of 3 to 4 months. There is a distinct seasonal variation with greater and more frequent swelling occurring during summer months compared with winter. Explanation for swelling includes the growth of salt crystals in rock lattices and expansion from wetting and drying. Warm summer temperatures provide the best conditions for both processes. Swelling appears to be an important precursor to erosion of material from shore platform surfaces. The conclusion drawn is that subaerial weathering makes an important contribution to the lowering of the shore platforms on the Kaikoura Peninsula.

Influence of along‐shore advection and upwelling on coastal temperature at Kaikoura Peninsula, New Zealand

Thermistor data from around Kaikoura Peninsula, New Zealand, show that in the synoptic band, temperature fluctuations at 1 m are coherent with the along‐shore wind with a 90° phase difference. At 5 m, however, the coherence is not as high, and the phase relationship is in the opposite sense. Along this coast, wind‐driven advection of the coastal current and upwelling have opposite effects on temperature. A simple model is developed which has along‐shore advection and upwelling terms parameterised in terms of the wind and two unknown coefficients. Solving for the coefficients shows that at 1 m, temperature variability is determined by along‐shore advection, whereas at 5 m, temperature variability is determined principally by upwelling.

Development of shore platforms on Kaikoura Peninsula, South Island, New Zealand: Part One: The role of waves

The role of waves in shore platform development has been investigated on Kaikoura Peninsula by direct measurement of waves in deep water and on platforms at high tide. This showed that the deepwater wave environment off the Kaikoura Peninsula is very energetic, but the amount of energy delivered to platforms is very low. In deep water, wave power ranged from 5900 to 106 700 N m s −1 per m of crest when calculated from mean significant wave height and when calculated from maximum wave height it ranged from 31 400 to 5 370 000 N m s −1 per m of crest. A comparison of deep water wave energy flux with wave energy flux at the high tide cliff of platforms showed that there was a reduction by as much as five orders of magnitude during storm conditions. An analysis of the role of breaking waves revealed that these are ineffective as an erosional agent because the depth of water offshore causes breaking before waves arrive on platform surfaces. Depth of water controlling wave breaking causes larger storm waves to break further from shore, preventing direct attack at the cliff base. Shear stresses and dynamic forces under waves were calculated from waves measured on shore platforms. This showed that these forces never exceeded the compressive strength of the platform rocks at Kaikoura. It is concluded that wave forces are not directly capable of causing erosion on shore platforms at Kaikoura.