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The evolution of the continental intraarc Taupo Rift in the North Island, New Zealand, is rapid, significantly faster than comparative intracontinental rifts such as the African Rifts. Based on our faulting data and published geological, geophysical, and borehole data, we show that activity in the ~2 Ma Taupo Rift has rapidly and asymmetrically narrowed via inward and eastward migration of faulting (at rates of approximately 30 km Myr−1 and 15 km Myr−1, respectively) and has propagated southward along its axis ~70 km in 350 kyr. The loci of voluminous volcanic eruptions and active faulting are correlated in time and space, suggesting that a controlling factor in the rapid rift narrowing is the presence of large shallow heterogeneities in the crust, such as large rhyolitic magma bodies generated by subduction processes, which weaken the crust and localize deformation. Eastward migration of faulting also follows the eastward migration of the volcanic arc which may be related to rollback of the Pacific crust slab at the Hikurangi subduction zone. Southward propagation of the rift is linked with southward migration of the Hikurangi Plateau/Chatham Rise subduction point and occurs episodically aided by stress changes associated with voluminous local volcanism. The large magma supply during early continental intraarc rift stages explains faster evolution (from tectonic to magmatic) than intracontinental rifts. However, the fast changes in magma supply from the subduction zone can also lead to evolution reversals (more evolved magmatic stages reverting to less evolved tectonic stages), rift cessation, and thus failed continental breakup. [ABSTRACT FROM AUTHOR]

At the eastern boundary of the south Taupo Rift, the NE-striking, rift-bounding Rangipo and the ENE-striking Wahianoa active normal faults intersect. We investigate their intersection at the Upper Waikato Stream to understand the kinematics of a rift termination in an active volcanic area. The Upper Waikato Stream Fault is a previously unrecognised seismogenic source also at the eastern boundary, capable of producing aMW6.5 and up toMW7.1 earthquake if it ruptures in conjunction with the Rangipo or Wahianoa faults. We found a minimum of 12 surface-rupturing earthquakes in the last 45.16 ka on the Upper Waikato Stream Fault (mean slip-rate c. 0.5 mm/yr), and a minimum of nine surface-rupturing earthquakes in the last 133 ka on the Wahianoa Fault (mean slip-rate c. 0.2 mm/yr). Periods of highest slip-rate on these faults may coincide in time with Taupo, Ruapehu or Tongariro eruptions, but, despite their intersection, movement was not coincident across all faults. The Upper Waikato Stream Fault responded to a major Taupo Volcano eruption, the Wahianoa to a major eruptive sequence from Mt Tongariro and the Rangipo to major explosive events from Mt Ruapehu. [ABSTRACT FROM PUBLISHER]

OBJECTIVES: To report on oral-health-related characteristics, beliefs, and behaviours among participants in a randomised control trial of an intervention to prevent early childhood caries (ECC) among Maori children, and to determine whether there were any systematic differences between the intervention and control groups at baseline. DESIGN: Baseline measurements from a randomised control trial (involving 222 pregnant Maori women allocated randomly to either Intervention or Delayed groups) which is currently underway. Setting: The rohe (tribal area) of Waikato-Tainui. METHODS: Self-report information collected on sociodemographic characteristics, pregnancy details, self-reported general and oral health and health-related behaviours, and oral health beliefs. RESULTS: Other than those in the Delayed group being slightly older, on average, there were no significant differences between the two groups. Some 37.0% were expecting their first child. Most reported good health; 43.6% were current smokers, and 26.4% had never smoked. Only 8.2% were current users of alcohol. Almost all were dentate, and 57.7% described their oral health as fair or poor. One in six had had toothache in the previous year; 33.8% reported being uncomfortable about the appearance of their teeth, and 27.7% reported difficulty in eating. Dental service-use was relatively low and symptom-related; 78.9% needed to see a dentist. Overall, most of the sample believed that it was important to avoid sweet foods, visit dentists and to brush the teeth, while about half thought that using fluoride toothpaste and using floss were important. Some 38.2% felt that drinking fluoridated water was important. Oral-health-related fatalism was apparent, with 74.2% believing that most people usually get dental problems, 58.6% believing that most people will need extractions at some stage, and that most children eventually get dental caries. CONCLUSIONS: Mothers' important role in nurturing the well-being of the young child includes the protection and maintenance of the growing child's oral health (or ukaipo niho). The findings provide important insights into Maori mothers' oral health knowledge, beliefs and practices. [ABSTRACT FROM AUTHOR]

Active fault traces are a surface expression of permanent deformation that accommodates the motion within and between adjacent tectonic plates. We present an updated national-scale model for active faulting in New Zealand, summarize the current understanding of fault kinematics in 15 tectonic domains, and undertake some brief kinematic analysis including comparison of fault slip rates with GPS velocities. The model contains 635 simplified faults with tabulated parameters of their attitude (dip and dip-direction) and kinematics (sense of movement and rake of slip vector), net slip rate and a quality code. Fault density and slip rates are, as expected, highest along the central plate boundary zone, but the model is undoubtedly incomplete, particularly in rapidly eroding mountainous areas and submarine areas with limited data. The active fault data presented are of value to a range of kinematic, active fault and seismic hazard studies. [ABSTRACT FROM AUTHOR]

The Canterbury earthquake sequence of 2010–2011 is the most significantly impacting event in New Zealand since World War II, consuming >15% of New Zealand's GDP. In Canterbury, geoscience information has contributed significantly to civil defence response management and more recently to the recovery effort coordinated through the Canterbury Earthquake Recovery Authority (CERA) and local authorities in Canterbury. The earthquakes have resulted in major social, community, education and economic disruption, and created considerable uncertainty in relation to the feasibility of land remediation in liquefaction-damaged areas. Analysis of voluminous geoscience, engineering and social science data has and will continue to underpin decisions on the appropriate time to begin infrastructure, residential and commercial rebuild and on whether building codes are appropriate to protect society from rare but potentially catastrophic events. [ABSTRACT FROM PUBLISHER]

The article discusses a study on the temporal associations between single volcanic eruptions from Okataina volcanic center (OVC) and normal fault ruptures in the northern sector of the Taupo rift in New Zealand. The researchers examined evidence for volcano-tectonic interactions. They reviewed the eruptive history of the OVC. They found associations between the timing of fall tephra on the fault scarp. They also observed that ruptures have no relationship with tephra deposition.

Coastlines that trend both parallel and normal to the Hikurangi subduction margin along the Raukumara Peninsula, New Zealand, provide a globally unique situation that enables study of the coastal deformation and its spatial variance across and along the forearc. The data suggest there is margin-parallel zoning of the forearc deformation processes across the Raukumara segment of the Hikurangi margin. On forearc promontories closest to the Hikurangi trench (within 80 km), Holocene marine and fluvial terraces record localised zones of intermittent uplift driven by large coseismic events on landward-dipping nearshore reverse faults. At greater distances from the trench (>100 km), Holocene and Pleistocene coastal stratigraphy and geomorphology suggest that surface uplift occurs by a gradual mechanism: either by frequent small earthquakes or by an aseismic process. In concurrence with geophysical models, we suggest the gradual uplift of this area is most likely driven by the buoyancy of underplated sediment with a contribution from subduction of the over-thickened crust of the Hikurangi Plateau. There is an intermediate zone at c. 80-100 km from the trench that is uplifted at low to moderate rates, probably by the effects of Hikurangi Plateau subduction with some contributions from outboard upper plate faulting and inboard sediment underplating. [ABSTRACT FROM AUTHOR]

Six trenches and additional exposures have been investigated along a 23 km length of the Pahiatua section of the Wellington Fault. The sites show a consistent fault rupture record for the last four surface-faulting events along the Pahiatua section. This multi-site record of events, supported by 28 radiocarbon ages that span the last c. 4500 yr, is the most complete paleoseismic record for the Wellington Fault. From southwest to northeast, the trenches are called death-1 and -2, Hughes-2 and -1, and ebbett-2 and -1, named after local farmers. Additional data come from an exposure at the Army Depot northeast of Ebbett-1 and a stream cutting near the Death-1 trench. Earthquake events are recognised on the basis of upward terminations of faults and stratigraphic evidence (unconformities; scarp-derived colluvial deposits; "co-seismically" generated, organic, poorly sorted units; and subsequent scarp-ponded units). On this basis, evidence for the most recent surface-faulting event is recognised at all sites (i.e., between death-1 and the army depot site) and has a timing of ad 1670-1800 (150-280 cal. yr BP). The penultimate faulting event has been recognised at all six trenches and occurred between ad 690 and 1170 (780-1260 cal. yr BP). Clear evidence, and datable material associated with events III and IV, is observed only in the older records of the Ebbett-1 and Hughes trenches. Event iii is bracketed by faulting and two ages on co-seismic deposits to the interval ad 65 to 400 BC (1885-2350 cal. yr BP). Event IV is bracketed by three key ages in the Hughes-1 trench to the interval 1600-2140 BC (3550-4090 cal. yr BP). The trench-derived recurrence interval based on these four events is c. 1200 ± 110 yr, which is consistent with, though longer than, an estimate of the recurrence interval based on slip rate (5.1-6.2 mm/yr) and single-event displacement (4.5 ± 1 m), which gave a range of 820 ± 260 yr. When the current paleoseismic data for the Wellington Fault are considered together, they suggest that: (1) the last four large earthquakes along the Pahiatua section have involved rupture of the entire section; (2) these events broadly correlate with other dated paleoearthquake events along the Wellington-Hutt Valley segment and Tararua section of the fault, and the southern end of the Mohaka Fault; (3) the most recent faulting event along the Pahiatua section is somewhat younger than for the Wellington-Hutt Valley segment or Tararua section; and (4) either single or dual segment/section rupture scenarios existed along these four fault sections. [ABSTRACT FROM AUTHOR]

To understand the tectonic evolution of the southern termination of the Taupo Volcanic Zone (TVZ), New Zealand, we compare the late Quaternary structure and kinematics of the southern part of the Taupo Rift or Taupo Fault Belt (Mt Ruapehu Graben) with central parts of the rift (Ngakuru Graben), and with the South Wanganui Basin. We also investigate the differences between displacements of Pliocene and late Quaternary markers within the southern Taupo Rift. Comparison of fault displacement rates derived from displacements of late Quaternary and Pliocene markers yields a preliminary estimate of <400 000 yr for fault initiation of the majority of faults in the southern Taupo Rift. The timing of the onset of faulting in the southern TVZ appears to be younger than central parts of the TVZ and may indicate a step-wise southward propagation of the rift. Faulting also appears to be less evolved in the south than in the central parts of the Taupo Rift (thicker seismogenic crust and hence wider fault spacing), reinforcing the impression of a recent incremental propagation of the Taupo Rift to the south. The onset of faulting coincides with independent observations of the initiation of volcanism in the southern TVZ. We propose that the termination of the TVZ, geographically short of the limit of the Hikurangi margin, may only be temporary, and it is most likely to propagate southward in association with future major perturbations in the subduction margin, such as the occurrence of large ignimbrite volcanism. [ABSTRACT FROM AUTHOR]

Late Quaternary structure and kinematics at the southern termination of the Taupo Rift are investigated by means of active fault mapping and estimates of fault displacement and extension rates. Active faults in the southern Taupo Rift are normal in sense and include three major structures: the NNE-trending Mt Ruapehu Graben; the E-W to ESE-WNW-trending Ohakune-Raetihi fault set; and the NE-trending Karioi fault set. Displacements of young geomorphic features, fault plane exposures in roadcuts, and trenches across faults show that all faults are active contemporaneously. The Mt Ruapehu Graben is the southern extension of the modern (i.e., <26 ka) Taupo Rift (or Taupo Fault Belt, TFB), and has developed as a result of backarc extension related to the Hikurangi subduction margin. Geologic extension rate for the Mt Ruapehu Graben is estimated here at 2.3 ± 1.2 mm/yr. The other two structures strike almost perpendicular to the Taupo Rift terminating the Mt Ruapehu Graben to the south. The co-existence of three normal fault sets in mutual crosscutting relations and with no significant strike-slip on any of them may be related to local reorientation of the minimum principal stress axis (σ3) or to a stress tensor where |σ3| ≈ |σ2|. Complicated strains at the southern termination of the Taupo Rift are related to block rotations in the Hikurangi subduction margin. [ABSTRACT FROM AUTHOR]

A sedimentary sequence that was highly sensitive to fault rupture-driven changes in water level and sediment supply has been used to extract a continuous record of 22 large earthquakes on the Alpine fault, the fastest-slipping fault in New Zealand. At Hokuri Creek, in South Westland, an 18 m thickness of Holocene sediments accumulated against the Alpine fault scarp from ca. A.D. 800 to 6000 B.C. We used geomorphological mapping, sedimentology, and paleoenvironmental reconstruction to investigate the relationship between these sediments and Alpine fault rupture. We found that repeated fault rupture is the most convincing mechanism for explaining all the features of the alternating peat and silt sedimentary sequence. Climate has contributed to sedimentation but is unlikely to be the driver of these cyclical changes in sediment type and paleoenvironment. Other nontectonic causes for the sedimentary alternations do not produce the incremental increase in basin accommodation space necessary to maintain the shallow-water environment for 6800 yr. Our detailed documentation of this near-fault sedimentary basin sequence highlights the advantages of extracting paleoearthquake records from such sites--the continuity of sedimentation, abundance of dateable material, and pristine preservation of older events. [ABSTRACT FROM AUTHOR]