GNS Science Research Articles

Conceptual Development of a National Volcanic Hazard Model for New Zealand

We provide a synthesis of a workshop held in February 2016 to define the goals, challenges and next steps for developing a national probabilistic volcanic hazard model for New Zealand. The workshop involved volcanologists, statisticians, and hazards scientists from GNS Science, Massey University, University of Otago, Victoria University of Wellington, University of Auckland, and University of Canterbury. We also outline key activities that will develop the model components, define procedures for periodic update of the model, and effectively articulate the model to end-users and stakeholders. The development of a National Volcanic Hazard Model is a formidable task that will require long-term stability in terms of team effort, collaboration and resources. Development of the model in stages or editions that are modular will make the process a manageable one that progressively incorporates additional volcanic hazards over time, and additional functionalities (e.g. short-term forecasting). The first edition is likely to be limited to updating and incorporating existing ashfall hazard models, with the other hazards associated with lahar, pyroclastic density currents, lava flow, ballistics, debris avalanche, and gases/aerosols being considered in subsequent updates.

New Zealand\u2019s National Landslide Database

A New Zealand Landslide Database has been developed to hold all of New Zealand’s landslide data and provide factual data for use in landslide hazard and risk assessment, including a probabilistic landslide hazard model for New Zealand, which is currently being developed by GNS Science. Design of a national Landslide Database for New Zealand required consideration of existing landslide data stored in a variety of digital formats and future data yet to be collected. Pre-existing landslide datasets were developed and populated with data reflecting the needs of the landslide or hazard project, and the database structures of the time. Bringing these data into a single database required a new structure capable of containing landslide information at a variety of scales and accuracy, with many different attributes. A unified data model was developed to enable the landslide database to be a repository for New Zealand landslides, irrespective of scale and method of capture. Along with landslide locations, the database may contain information on the timing of landslide events, the type of landslide, the triggering event, volume and area data, and impacts (consequences) for each landslide when this information is available. Information from contributing datasets include a variety of sources including aerial photograph interpretation, field reconnaissance and media accounts. There are currently 22,575 landslide records in the database that include point locations, polygons of landslide source and deposit areas, and linear landslide features. Access to all landslide data is provided with a web application accessible via the Internet. This web application has been developed in-house and is based on open-source software such as the underlying relational database (PostGIS) and the map generating Web Map Server (GeoServer). Future work is to develop automated data-upload routines and mobile applications to allow people to report landslides, adopting a consistent framework.

Molecular carbon nitride ion beams for enhanced corrosion resistance of stainless steel

A novel approach is presented for molecular carbon nitride beams to coat stainless surfaces steel using conventional safe feeder gases and electrically conductive sputter targets for surface engineering with ion implantation technology. GNS Science’s Penning type ion sources take advantage of the breaking up of ion species in the plasma to assemble novel combinations of ion species. To test this phenomenon for carbon nitride, mixtures of gases and sputter targets were used to probe for CN+ ions for simultaneous implantation into stainless steel. Results from mass analysed ion beams show that CN+ and a variety of other ion species such as CNH+ can be produced successfully. Preliminary measurements show that the corrosion resistance of stainless steel surfaces increased sharply when implanting CN+ at 30keV compared to reference samples, which is interesting from an application point of view in which improved corrosion resistance, surface engineering and short processing time of stainless steel is required. The results are also interesting for novel research in carbon-based mesoporous materials for energy storage applications and as electrode materials for electrochemical capacitors, because of their high surface area, electrical conductivity, chemical stability and low cost.

The age of the Takatika Grit, Chatham Islands, New Zealand

Hollis, C.J, Stickley, C.E., Bijl, P.K., Schiøler, P., Clowes, C.D., Li, X, Campbell, H. March 2017. The age of the Takatika Grit, Chatham Islands, New Zealand. Alcheringa 41, xxx–xxx. ISSN 0311-5518.The oldest Paleogene strata on Chatham Islands, east of New Zealand, are the phosphatized conglomerates and sandstones of the Takatika Grit that crops out on the northeastern coast at Tioriori and unconformably overlies the Chatham Schist. An intact Cretaceous–Paleogene boundary transition is not preserved at this locality. New biostratigraphic analysis of dinoflagellate, diatom and radiolarian microfossil assemblages confirms that the Takatika Grit is of late early–middle Paleocene (New Zealand Teurian stage) age but contains reworked microfossils of early Campanian (Early Haumurian) age. Vertebrate fossils found in this unit are inferred to be a mixture of reworked Cretaceous and in situ Paleocene bones and teeth. The overlying Tutuiri Greensand is of middle–late Paleocene age in its lower part and also contains reworked Cretaceous microfossils.Christopher J. Hollis [c.hollis@gns.cri.nz], Chris Clowes [c.clowes@gns.cri.nz], Xun Li [x.li@gns.cri.nz], Hamish Campbell [h.campbell@gns.cri.nz], GNS Science, PO Box 30-368, Lower Hutt 5040, New Zealand; Catherine Stickley, Evolution Applied Limited, 50 Mitchell Way, Upper Rissington, Cheltenham GL54 2PL, UK [catherine.stickley@gmail.com]; Peter Bijl [p.k.bijl@uu.nl], Marine Palynology and Paleoceanography, Department of Earth Sciences, Utrecht University, 3584 CS Utrecht, the Netherlands; Poul Schiøler [poul.schioler@mgpalaeo.com.au], Morgan Goodall Palaeo, Unit 1/5 Arvida St, Malaga, WA 6090, Australia.

Forecasting volcanic ash deposition using HYSPLIT

A major source of error in forecasting where airborne volcanic ash will travel and land is the wind pattern above and around the volcano. GNS Science, in conjunction with MetService, is seeking to move its routine ash forecasts from using the ASHFALL program, which cannot allow for horizontal variations in the wind pattern, to HYSPLIT, which uses a full 4-D atmospheric model. This has required some extensions to the standard version of the HYSPLIT program, both to get appropriate source terms and to handle the fall velocities of ash particles larger than 100 microns.Application of the modified HYSPLIT to ash from the Te Maari eruption of 6 August 2012 from Tongariro volcano gives results similar to the observed ash distribution. However, it was also apparent that the high precision of these results could be misleading in actual forecasting situations, and there needs to be ways in which the likely errors in atmospheric model winds can be incorporated into ash models, to show all the areas in which there is a significant likelihood of deposited ash with each particular volcanic eruption model.

Offshore Rayleigh group velocity observations of the South Island, New Zealand, from ambient noise data

We thank Captain and Crew of the R/V Thomas G. Thompson (cruise TN229), the R/V Roger Revelle (cruise RR1002), and the SIO OBSIP facility for expert assistance at sea. The OBS instruments used in this field program were provided by the U.S. National Ocean Bottom Seismic Instrumentation Pool (http://www.obsip.org). MOANA seismic data are archived at the IRIS Data Management Center. The collection of ocean bottom seismic data was funded by the National Science Foundation under grants EAR-0409564, EAR-0409609, and EAR-0409835. New Zealand onshore seismic data made available by the GeoNet project, sponsored by EQC, GNS Science, and LINZ. J. Stachnik acknowledges support from the CIRES postdoctoral fellowship program.. F.-C. Lin was supported by NSF grant CyberSEES- 1442665 and the King Abdullah University of Science and Technology (KAUST) under award OCRF-2014-CRG3- 2300. We thank Martha Savage, Dan Zietlow, Justin Ball, Craig Jones, Bill Fry, and Peter Molnar for valuable comments and discussion, and John Collins for leading the MOANA OBS experiment. We thank two anonymous reviewers and Editor Mike Ritzwoller for their constructive comments.

Te Tarata and Te Otukapuarangi: Reverse engineering Hochstetter’s Lake Rotomahana Survey to map the Pink and White Terrace locations

The Pink and White Terraces were New Zealand’s eighth wonder of the world, until the Tarawera eruption on 10 June 1886 engulfed them. Without pre-eruption survey data, scientific and government teams failed to relocate the terraces, which were assumed lost. Over 2011-2012 GNS Science announced the rediscovery of parts of both terraces in Lake Rotomahana: however, by 2016 they resiled these claims, concluding the majority of both terraces destroyed.This paper maps their original locations based on reverse engineering unpublished 1859 survey data from Ferdinand von Hochstetter. Evidence suggests the locations may have survived the eruption, with the terraces buried in ash, crossing the shoreline on land not subject to local volcanic cratering. Excavation is conceivable. The Pink and White Terraces may again delight visitors in Rotorua via the Terraces Track, complementing the world-class New Zealand walking tracks.

Molluscan death assemblages from uplifted Holocene terraces, Mahia Peninsula, New Zealand, interpreted from present-day intertidal ecology

Beu, A.G., August 2016. Molluscan death assemblages from uplifted Holocene terraces, Mahia Peninsula, New Zealand, interpreted from present-day intertidal ecology. Alcheringa 41, xxx–xxx. ISSN 0311-5518.Macrofossils from cover beds of marine terraces at Table Cape, Mahia Peninsula, uplifted coseismically ca 250, 1400, 1850 and 3500 years ago are compared with the fauna living on the nearby 200-m-wide intertidal rock platform. The inner platform is dry at low tide, apart from shallow pools containing Diloma aethiops and abundant but unexpected specimens of Zeacumantus subcarinatus and Cominella glandiformis exposed to the sun; all are common fossils in the terrace cover beds. The outer platform is carpeted densely with the alga Hormosira and shelters a diverse fauna, again all common fossils in the terrace cover beds. Sand and gravel containing shell fragments and supporting Zostera sea-grass turf unexpectedly covers ca 5% of the platform in low areas along the east coast. The fossil fauna is listed from 47 samples from two trenches excavated east–west and north–south through the terrace cover beds. Death assemblages of 158 molluscs, including 24 new records as fossils, and 11 taxa in other phyla delimit sediment derived from four shell accumulation sites identified around the present cape: storm beach, high-tidal strand line, hollows in the rock platform and Zostera flats. Up to 32 of the 47 samples (68%) possibly were deposited in Zostera flats; the rest were sand beach accumulations deposited at and near the high-tidal strand line. All fossils common in the cover beds lived on the rock platform. Differences between the deposits in the two trenches result from two factors. Protection along the east coast by protruding tephra beds and an outer rampart armoured with the macroalga Durvillaea prevented erosion of Zostera-supporting sediment which, therefore, was retained after each uplift event. The exposed eastern position of Table Cape also caused sediment to be transported predominantly westwards, onshore on the east coast but away from Table Cape along the north coast.A.G. Beu [a.beu@gns.cri.nz], Paleontology Department, GNS Science, PO Box 30368, Lower Hutt 5040, New Zealand.

Revisiting the Canterbury earthquake sequence after the 14 February 2016 Mw 5.7 event

AbstractOn 14 February 2016, an Mw 5.7 (GNS Science moment magnitude) earthquake ruptured offshore east of Christchurch, New Zealand. This earthquake occurred in an area that had previously experienced significant seismicity from 2010 to 2012 during the Canterbury earthquake sequence, starting with the 2010 Mw 7.0 Darfield earthquake and including four Mw ~6.0 earthquakes near Christchurch. We determine source parameters for the February 2016 event and its aftershocks, relocate the recent events along with the Canterbury earthquakes, and compute Coulomb stress changes resolved onto the recent events and throughout the greater Christchurch region. Because the February 2016 earthquake occurred close to previous seismicity, the Coulomb stress changes resolved onto its nodal planes are uncertain. However, in the greater Christchurch region, there are areas that remain positively loaded, including beneath the city of Christchurch. The recent earthquake and regional stress changes suggest that faults in these regions may pose a continuing seismic hazard.

Petlab: New Zealand’s national rock catalogue and geoanalytical database

ABSTRACTThe Petlab database is New Zealand’s online national rock and analytical database, and provides an accessible, structured and permanent data repository for the local and global geoscience communities. The database contains locations, descriptions and analyses of rock and mineral samples from onland New Zealand, the offshore New Zealand region, Antarctica and worldwide. It is operated by GNS Science and, as a nationally significant database, currently receives core funding from central government. The major data contributors are GNS Science and Auckland, Massey, Waikato, Victoria, Canterbury and Otago universities, all of whom use the database as a digital catalogue for their rock and mineral collections. Petlab sample information and geoanalytical data can be uploaded, queried, viewed and downloaded at http://pet.gns.cri.nz. Petlab is a valuable tool for geoscientists in research and industry.

Book review: <i>James Hector. Explorer, Scientist, Leader</i>

This book is by a prominent New Zealand geologist and science historian about one of the leading 19th century scientists, James Hector (1834–1907). His influence on New Zealand’s science in the second half of the century was so dominant that one science historian called this period “Hector hegemony”. But contrary to his contemporary, the German-born scientist Julius Haast, the full story of Hector’s achievements for New Zealand’s science had never been told and his name survived mainly in connection with the Hector dolphin, an endangered endemic species that he was the first to describe. But as of now, Nathan’s book will fill this gap. This is a well written, aptly designed and richly illustrated chronological biography of Hector’s life and work. It is remarkable how many details were unearthed from a large number of archives and libraries and especially from the letters Hector exchanged with friends and colleagues, mostly with Julius Haast, director of the Canterbury Museum at Christchurch, and Joseph Hooker, director of the Royal Botanic Gardens at Kew, UK; Nathan had previously edited the correspondence of Hector and Haast and a bibliography of Hector’s publications prior to the book under review (Nathan et al., 2012, 2015). James Hector was born in Edinburgh; he graduated from his home university in 1856 as a doctor of medicine and developed a strong interest in geology, biology and tramping. Consequently, his first involvement in a major scientific exploration led him to Western Canada, where he joined an expedition into the Canadian Rockies with the aim of finding a suitable pass for the railway to connect the western Prairies with the Pacific. The pass discovered by this expedition is still in use; its name “Kicking Horse Pass” recalls an incident which almost cost Hector his life. His reputation as a keen and successful explorer reached the distant colony of New Zealand. In the 1860s, the Otago Provincial Council at Dunedin initiated a geological survey of the province with the aim of detecting new mineral and coal deposits and a suitable route linking the province of Otago to the remote west coast. Hector was appointed as government scientist and arrived in Dunedin in 1862. After an effective exploration on land and sea he served as one of the curators for the New Zealand Exhibition in Dunedin in 1865. In the same year, he arrived in Wellington as a government employee. Nathan’s book marks the 150th anniversary of Hector’s appointment as New Zealand’s first government scientist, the year when the seat of government was moved from Auckland to Wellington. From this year on, Hector was the great organiser of New Zealand’s science. At first he was involved in the foundation of a colonial museum, the forerunner of Te Papa, which is now New Zealand’s National Museum; he organised the central New Zealand Institute, which included the publication of the annual and influential Transactions and Proceedings. He masterminded the first comprehensive New Zealand Geological Survey (now GNS Science), which resulted in the publication of the first Geological Map of New Zealand. Hector also became the conductor and supervisor of the Colonial Botanical Gardens, the Colonial Observatory and was director of the meteorological stations. He used the expanding telegraph network to establish a nationwide recording system for the location and intensity of earthquakes. Hector was a foundation member of the Council and Chancellor of the University of New Zealand, and he was knighted in 1887. All these and a number of various other achievements are the topic of separate chapters in Nathan’s book, and they underline the outstanding importance of a scientist whom a newspaper once called “a man who knows everything” (p. 12).

Improved Rapid Magnitude Estimation for a Community‐Based, Low‐Cost MEMS Accelerometer Network

Immediately following the M w 7.2 Darfield, New Zealand, earthquake, over 180 Quake‐Catcher Network (QCN) low‐cost micro‐electro‐mechanical systems accelerometers were deployed in the Canterbury region. Using data recorded by this dense network from 2010 to 2013, we significantly improved the QCN rapid magnitude estimation relationship. The previous scaling relationship (Lawrence et al. , 2014) did not accurately estimate the magnitudes of nearby (<35 km) events. The new scaling relationship estimates earthquake magnitudes within 1 magnitude unit of the GNS Science GeoNet earthquake catalog magnitudes for 99% of the events tested, within 0.5 magnitude units for 90% of the events, and within 0.25 magnitude units for 57% of the events. These magnitudes are reliably estimated within 3 s of the initial trigger recorded on at least seven stations. In this report, we present the methods used to calculate a new scaling relationship and demonstrate the accuracy of the revised magnitude estimates using a program that is able to retrospectively estimate event magnitudes using archived data. Online Material: Table of magnitude estimates for Quake‐Catcher Network‐detected events, and figures clarifying the linear fitting technique used to calculate the Chung et al. revised scaling relationship.

XCAMS: The compact 14C accelerator mass spectrometer extended for 10Be and 26Al at GNS Science, New Zealand

A detailed description is given of the 0.5MV tandem accelerator mass spectrometry (AMS) system for 10Be, 14C, 26Al, installed in early 2010 at GNS Science, New Zealand. Its design follows that of previously commissioned Compact 14C-only AMS (CAMS) systems based on the Pelletron tandem accelerator. The only basic departure from that design is an extension of the rare-isotope achromat with a 45° magnet and a two-anode gas-ionisation detector, to provide additional filtering for 10Be. Realised performance of the three AMS modes is discussed in terms of acceptance-test scores, 14C Poisson and non-Poisson errors, and 10Be detection limit and sensitivity. Operational details and hardware improvements, such as 10Be beam transport and particle detector setup, are highlighted. Statistics of repeat measurements of all graphitised 14C calibration cathodes since start-up show that 91% of their total uncertainty values are less than 0.3%, indicating that the rare-isotope beamline extension has not affected precision of 14C measurement. For 10Be, the limit of detection in terms of the isotopic abundance ratio 10Be/9Be is 6×10−15atat−1 and the total efficiency of counting atoms in the sample cathode is 1/8500 (0.012%).

High-Precision Atmospheric 14 CO 2 Measurement at the Rafter Radiocarbon Laboratory

This article describes a new capability for high-precision 14 C measurement of CO2 from air at the Rafter Radiocarbon Laboratory, GNS Science, New Zealand. We evaluate the short-term within-wheel repeatability and long-term between-wheel repeatability from measurements of multiple aliquots of control materials sourced from whole air. Samples are typically measured to 650,000 14C counts, providing a nominal accelerator mass spectrometry (AMS) statistical uncer- tainty of 1.3‰. No additional uncertainty is required to explain the within-wheel variability. An additional uncertainty factor is needed to explain the long-term repeatability spanning multiple measurement wheels, bringing the overall repeatability to 1.8‰, comparable to other laboratories measuring air materials to high precision. This additional uncertainty factor appears to be due to variability in the measured 14 C content of OxI primary standard targets, likely from the combustion process. We observe an offset of 1.4‰ in our samples relative to those measured by the University of Colorado INSTAAR, comparable to interlaboratory offsets observed in recent intercomparison exercises. This article describes the high-precision atmospheric 14 CO 2 measurement capability at the Rafter Radiocarbon Laboratory at GNS Science, New Zealand. We discuss the two different methods we commonly use for CO 2 collection and subsequent extraction. We describe our recently upgraded graphitization system and detail our measurement protocols for samples requiring high precision. We use replicate measurements of CO 2 from a number of different control materials, all derived from whole air, to examine mean values and offsets between different standardization methods within our laboratory, as well as interlaboratory offsets based on an ongoing intercomparison with the University of Colorado INSTAAR. We then examine short-term within-wheel and long-term repeatability of our measurements, and the sources of uncertainty that contribute to these. METHODS CO 2 from air is collected either by in situ absorption of CO 2 into sodium hydroxide (NaOH) solution or by collection of whole air into flasks or pressurized cylinders. In addition, control materials, pri - mary standards, and process blanks are routinely analyzed. In this section, we describe the collection methods and protocols for extracting and purifying the CO 2 in the laboratory.

High-Precision Atmospheric 14CO2 Measurement at the Rafter Radiocarbon Laboratory

This article describes a new capability for high-precision 14C measurement of CO2 from air at the Rafter Radiocarbon Laboratory, GNS Science, New Zealand. We evaluate the short-term within-wheel repeatability and long-term between-wheel repeatability from measurements of multiple aliquots of control materials sourced from whole air. Samples are typically measured to 650,000 14C counts, providing a nominal accelerator mass spectrometry (AMS) statistical uncertainty of 1.3‰. No additional uncertainty is required to explain the within-wheel variability. An additional uncertainty factor is needed to explain the long-term repeatability spanning multiple measurement wheels, bringing the overall repeatability to 1.8‰, comparable to other laboratories measuring air materials to high precision. This additional uncertainty factor appears to be due to variability in the measured 14C content of OxI primary standard targets, likely from the combustion process. We observe an offset of 1.4‰ in our samples relative to those measured by the University of Colorado INSTAAR, comparable to interlaboratory offsets observed in recent intercomparison exercises.

Report of the 2nd G-EVER International Symposium and the 1st IUGS and SCJ International Workshop on Natural Hazards and the “Sendai Agreement”

The 2nd G-EVER International Symposium and the 1st IUGS & SCJ International Workshop on Natural Hazards aimed to encourage extensive discussions on the present situation of natural disaster mitigation of earthquake, tsunami, volcanic eruption and landslide in the Asia and Pacific regions. The discussions included (1) prioritization of important researches to make society strong and resilient, (2) development of suitable hazard maps which are essential to society and Asia-Pacific scale hazard assessment activities, and (3) the importance of contributions to solid earth science. There were also discussions on the mitigation processes needed in the next-decade to reduce the risks of natural hazards. The 2nd G-EVER International Symposium and the 1st IUGS & SCJ International Workshop on Natural Hazards was held in Sendai, Tohoku, Japan on Oct. 19-20, 2013 (Fig. 1). The symposium was organized by the G-EVER Consortium, Geological Survey of Japan, AIST, the International Union of Geological Sciences (IUGS) and Science Council of Japan (SCJ). It was co-organized by the Geological Society of Japan and the Coordinating Committee for Geoscience Programmes in East and Southeast Asia (CCOP). Tohoku University, Disaster Prevention Research Institutes (DPRI) of Kyoto University, National Research Institute for Earth Science and Disaster Prevention (NIED), GNS Science, Philippine Institute of Volcanology & Seismology (PHIVOLCS), the Seismological Society of Japan, the Volcanological Society of Japan, Japan Association for Quaternary Research, Japanese Society for Active Fault Studies, Japan Society of Engineering Geology, and Tokyo Geographical Society supported the symposium (Fig. 2). The Asia-Pacific Region is an area with a high risk of catastrophic natural disasters such as earthquakes, tsunamis and volcanic eruptions. In today’s highly globalized economy, when a major disaster occurs, it can create unpredictable turmoil not just in the affected area but also the rest of the world. Countermeasures against these natural disasters are crucial for the sustainable development. We believe that continuous efforts to develop an effective international framework to reduce the risk of natural disasters are very important. It is expected that geological institutions will collaborate and create a system to gather and process information to formulate disaster mitigation measures in the Asia-Pacific Region. This system must be easy to use and freely accessible to the public to meet societal needs. The Sumatra earthquake of December 26, 2004 and Tohoku earthquake of March 11, 2011 clearly show the urgency of developing an information and knowledge system for infrequent natural hazards. We also have to recognize that smaller events could have adverse effect to society. For example, the magnitude of the February 2011 Christchurch earthquake was just 6.3 (ML), but caused major damage to the second largest city of New Zealand and 185 casualties. Volcanic ash ejected from the Eyjafjallajokull eruptions in Iceland on April 2000 caused more than 20,000 airline flight cancellations a day in Europe, resulting to the largest air-traffic shut-down since World War II. The IATA estimated that airline companies lost US$200 million a day during the shut-down. After the 2011 Tohoku earthquake, more efforts for the prevention and reduction of the risks of natural disasters have been made all over the world. The G-EVER Consortium promotes natural disaster risk reduction activities through the collaboration different research institutes worldwide. The consortium’s major activities are the following: 1. Establish a framework for cooperation of research institutes and organizations working on volcanic disaster prevention in the AsiaPacific region.

Geometric characterisation and out-of-plane seismic stability of low-rise unreinforced brick masonry buildings in Auckland, New Zealand

The 2010-2011 Canterbury earthquakes and corresponding Royal Commission reports have resulted in changes to the legislative environment and led to increased public awareness in New Zealand of the earthquake performance of unreinforced masonry (URM) buildings. As a result, building regulators, owners, tenants, users and heritage stakeholders will be facing a unique challenge in the near future where assessments, improvements and demolitions of URM buildings are expected to occur at an unusually high rate. Auckland is the largest city in New Zealand and because of the relative prosperity of Auckland during the period 1880-1935 when most URM buildings were being constructed in New Zealand, the city has the largest number of URM buildings in the country. Identifying those buildings most at seismic risk in Auckland’s large and varied building stock has warranted a rapid field assessment program supplemented by strategically chosen detailed assessments. Information that can be procured through rapid field inspections includes the building geometric typologies (e.g., heights, building footprint geometry and isolated versus row configuration), elevation type (e.g., perforated frame versus solid wall), wall construction (e.g., solid versus cavity, number of leaves) and basic construction material type (e.g., clay brick versus stone). Furthermore, investigation into the architectural history, heritage status and functional usage of Auckland’s URM buildings will affect the direction of retrofit strategies and priorities. As the owner of a large and varied portfolio of URM buildings as well as the local organisation responsible for assessing building safety, Auckland Council is developing exemplar inspection, assessment, prioritisation and retrofit strategies that will target the seismic risks associated with URM buildings, in particular, so as to preserve and enhance safety and the economic and community value of these special buildings. Collaboration amongst Auckland Council, The University of Auckland and GNS Science has resulted in a state-of-the-art rapid quantitative assessment program applied to a sampling of typologically representative URM buildings in Auckland.

Using regional moment tensors to constrain the kinematics and stress evolution of the 2010–2013 Canterbury earthquake sequence, South Island, New Zealand

On September 3, 2010, a MW 7.0 (U.S. Geological Survey moment magnitude) earthquake ruptured across the Canterbury Plains in South Island, New Zealand. Since then, New Zealand GNS Science has recorded over 10,000 aftershocks ML 2.0 and larger, including three destructive ~MW 6.0 earthquakes near Christchurch. We treat the Canterbury earthquake sequence as an intraplate earthquake sequence, and compare its kinematics to an Andersonian model for fault slip in a uniform stress field. We determined moment magnitudes and double couple solutions for 150 earthquakes having MW 3.7 and larger through the use of a waveform inversion technique using data from broadband seismic stations on South Island, New Zealand. The majority (126) of these double couple solutions have strike-slip focal mechanisms, with right-lateral slip on ENE fault planes or equivalently left-lateral slip on SSE fault planes. The remaining focal mechanisms indicate reverse faulting, except for two normal faulting events. The strike-slip segments have compatible orientations for slip in a stress field with a horizontal σ1 oriented ~N115°E, and horizontal σ3. The preference for right lateral strike-slip earthquakes suggests that these structures are inherited from previous stages of deformation. Reverse slip is interpreted to have occurred on previously existing structures in regions with an absence of existing structures optimally oriented for strike-slip deformation. Despite the variations in slip direction and faulting style, most aftershocks had nearly the same P-axis orientation, consistent with the regional σ1. There is no evidence for significant changes in these stress orientations throughout the Canterbury earthquake sequence.

Precursory characteristics of the seismicity before the 6 August 2012 eruption of Tongariro volcano, North Island, New Zealand

The 6 August 2012 eruption from the Upper Te Maari crater of Tongariro volcano followed approximately three weeks of precursory seismic activity. Earthquake relocations including data from extra temporary stations indicated that nearly all events were in a small area very close to Upper Te Maari. Most of these relocated events were very shallow, with nearly all events being between 1000 and 1500m below the ground surface.The pre-eruption seismicity occurred in three main swarms. During the first swarm on 12–13 July 2012, all the earthquakes had consistent inter-event times of 71±8min, while in the later swarms (17–20 and 29–30 July) many events had a similar pattern of consistent inter-event times. The stationary quasi-periodic (“clockwork”) earthquake process suggests that a single fracture point was excited by a nearly constant rate flux process.The dominant type of earthquake observed in these swarms had a sharp onset and a broad spectrum, with strong energy from 2 to 10Hz. Most events seen had a local magnitude of 1.5 to 2.5, with virtually no smaller events. Most of these earthquakes appeared to belong to a main earthquake family whose characteristics included a strong spectral component at about 2Hz and three bursts of energy spaced at intervals of about 1.5s. Of the 116 located earthquakes, 75 had a correlation coefficient greater than 0.70 with a master event. The spectra of these events did not change with size, with matching frequency peaks for all the events with a high correlation. The last event of this type was the day before the 6 August 2012 eruption, none have been seen since and there has been very little seismicity under Tongariro.This seismicity alerted GNS Science and other organisations to the unrest of Tongariro, and the Volcanic Alert Level and Aviation Colour Code were raised to publicise this. GNS Science also increased its monitoring of Tongariro, and discovered that the magmatic gas concentrations had increased compared to previous measurements in May 2012. However, the seismicity did not show any accelerating trend that suggested an immediate eruption threat, indicating the difficulty of predicting small eruptions in Tongariro and similar volcanoes.

Rapid Earthquake Characterization Using MEMS Accelerometers and Volunteer Hosts Following the M 7.2 Darfield, New Zealand, Earthquake

We test the feasibility of rapidly detecting and characterizing earthquakes with the Quake-Catcher Network (QCN) that connects low-cost microelectromechan- ical systems accelerometers to a network of volunteer-owned, Internet-connected com- puters. Following the 3 September 2010 M 7.2 Darfield, New Zealand, earthquake we installed over 180 QCN sensors in the Christchurch region to record the aftershock se- quence. The sensors are monitored continuously by the host computer and send trigger reports to the central server. The central server correlates incoming triggers to detect when an earthquake has occurred. The location and magnitude are then rapidly esti- mated from a minimal set of received ground-motion parameters. Full seismic time series are typically not retrieved for tens of minutes or even hours after an event. We benchmark the QCN real-time detection performance against the GNS Science GeoNet earthquake catalog. Under normal network operations, QCN detects and characterizes earthquakeswithin9.1softheearthquakeruptureanddeterminesthemagnitudewithin 1 magnitude unit of that reported in the GNS catalog for 90% of the detections.