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We combine previous studies, fieldwork, lidar data, and trenching to examine late Quaternary activity of the SE-dipping ≥23 km long Settlement Fault in the southeastern South Island. Trenching of a scarp crossing a small alluvial fan exposed a > 3 m thick sequence of folded sandy to silty fan alluvium. The uniformity of folding and four Optically Stimulated Luminescence dates indicate that these sediments were deposited relatively rapidly at ∼20 ka and subsequently accommodated 2.5 m of throw following ≥1 ruptures on an underlying buried reverse fault. Other key constraints on late Quaternary Settlement Fault activity are: (1) stranding of a shore platform at ∼3.7 ka, due to 1.5–2 m of fault uplift, and (2) a flat bedrock erosion surface overlain by loess and correlated to the last interglacial maximum (∼125 ka), indicating 0–4 m of fault uplift. From incorporating this information into a stochastic model of fault displacement accumulation we derive a slip rate of ∼0.02 mm/yr since 125 ka, and ∼0.27 mm/yr since 20 ka. We link the Settlement Fault’s current phase of heightened activity to a similarly timed increase in Akatore Fault activity, despite the tips of these faults being separated by between 9 and 25 km. [ABSTRACT FROM AUTHOR]

The New Zealand Community Fault Model (NZ CFM) is a publicly available representation of New Zealand fault zones that have the potential to produce damaging earthquakes. Compiled through collaborative engagement between New Zealand earthquake-science experts, this first edition (version 1.0) of the NZ CFM builds upon previous compilations of earthquake-source active fault models with the addition of new and modified information. Developed primarily to support an update of the New Zealand National Seismic Hazard Model, the NZ CFM comprises two principal components. The first dataset is a two-dimensional map representation of the surface traces of 880 generalised fault zones. Each fault zone is assigned specific geometric and kinematic attributes, including uncertainties, supplemented with a subjective quality ranking focused primarily on the confidence in assigned slip rates. The second component is a three-dimensional representation of the fault zones as triangulated mesh surfaces that are projected down-dip from the two-dimensional mapped traces to a geophysically-defined maximum fault rupture depth. This article summarises the compilation and parameterisation of the NZ CFM, along with background on its relation to predecessor datasets, and forward applications to probabilistic seismic hazard assessment and physics-based earthquake models currently being developed for Aotearoa New Zealand. [ABSTRACT FROM AUTHOR]

The Hundalee Fault forms part of the southeastern margin of the 2016 Kaikōura Earthquake rupture zone. Its late Quaternary activity and structural character may offer insights to fault interrelationships associated with the 2016 rupture. Mapping of the Hundalee Fault revealed several pre-existing fault scarps. Trenching of a scarp across a fluvial terrace together with radiocarbon dating shows the occurrence of at least two, probably three, surface ruptures since 3.5 ka. The scarp records about 2.5 m of reverse-sense vertical deformation, mostly folding, of which ∼0.6 m occurred in 2016, along with subordinate sinistral slip. Fluvial terrace ages inferred from geomorphological relationships, together with the trenching results, indicate a long-term vertical slip rate of 0.2–0.4 mm/yr since at least 30 ka. Geological data indicate a relatively recently surface emergence of the Hundalee Fault from beneath a fault propagation fold. The 2016 Hundalee Fault rupture is interpreted as a break-out from an extensive blind thrust fault, whose motion triggered predominantly contractional rupture of an array of steeper near-surface faults. The thrust is hypothesised as having provided linkage in the 2016 rupture between the predominantly strike-slip ruptures of The Humps Fault to the southwest and the Kekerengu Fault to the northeast. [ABSTRACT FROM AUTHOR]

This paper details the library special collections material held at the library of Highland Theological College, University of the Highlands and Islands. Our three main special collections are the primary focus of this article: the William Temple Collection, the Rutherford House Collection, and the Fort Augustus Collection. We detail here the story behind these collections entering our custody and proceed to highlight a selection of monographs of provenance and personal interest. This paper constitutes original research into the collections, building upon a foundation laid by the late college librarian, Mr. Martin Cameron (1955-2019), who curated the collections over some twenty years. We also discuss our ongoing work in formulating our new Historical Texts Collection, comprising the library's oldest books of academic interest, and a subcollection of liturgical music, isolated from the Fort Augustus Collection. [ABSTRACT FROM AUTHOR]

We present the first paleoseismic investigation of the Hyde Fault, one of a series of north-east striking reverse faults within the Otago range and basin province in southern New Zealand. Surface traces of the fault and associated geomorphology were mapped using a lidar digital elevation model and field investigations. Trenches were excavated at two sites across fault scarps on alluvial fan surfaces. The trenches revealed stratigraphic evidence for four surface-rupturing earthquakes. Optically stimulated luminescence dating constrains the timing of these events to around 47.2 ka (37.5–56.7 ka at 95% confidence), 34.6 ka (24.7–46.4 ka), 23.5 ka (19.7–27.3 ka) and 10.5 ka (7.9–13.1 ka). We obtain a mean inter-event time of 12.4 kyr (2.3–23.9 kyr at 95% confidence) and the slip rate is estimated to be 0.22 mm/yr (0.15–0.3 mm/yr). We do not find evidence to suggest that earthquake recurrence on the Hyde Fault is episodic, in contrast to other well-studied faults within Otago, suggesting diverse recurrence styles may co-exist in the same fault system. This poses challenges for characterising the seismic hazard potential of faults in the region, particularly when paleoearthquake records are limited to the most recent few events. [ABSTRACT FROM AUTHOR]

Reverse faulting in Otago, southern New Zealand, accommodates distributed tectonic convergence on the eastern side of the Australian‐Pacific plate boundary. Paleoearthquake records from some of the faults in the region show highly variable earthquake recurrence times, with long periods of quiescence separated by periods of earthquake activity. Here we develop a longer‐term context for these records, using cosmogenic radionuclide dating of faulted alluvial fan surfaces to characterize the late Quaternary slip rates on two significant faults within the system, the Hyde and Dunstan faults. We determine an average slip rate of 0.24 mm/yr (0.19–0.29 mm/yr at 95% confidence) for the Hyde Fault since about 115 ka, and an average slip rate of 0.16 mm/yr (0.12–0.21 mm/yr) for the Dunstan Fault since about 320 ka. Both faults show increases in slip rate of a factor of three to five times the average long‐term rate over timescales of 10 kyr. Increases in slip rate are out of phase on the two faults, supporting a hypothesis that strain is shared within the fault system over timescales on the order of 10 kyr. Over longer timescales, on the order of 100 kyr, slip rates can be well‐approximated by a linear fit, providing an upper limit on the variability of fault slip rates with time. Key Points: Cosmogenic radionuclide dating of faulted alluvial fans constrains slip rates for two reverse faults in southern New ZealandSlip rates are 0.24 mm/yr (0.19–0.29 mm/yr) for the Hyde Fault and 0.16 mm/yr (0.12–0.21 mm/yr) for the Dunstan FaultStrain sharing is suggested by changes in slip rates on 10 kyr timescales, while over longer timescales this variability averages out [ABSTRACT FROM AUTHOR]

We document the first use of fragile geologic features (FGFs) to set formal design earthquake motions for a major existing engineered structure. The safety evaluation earthquake (SEE) spectrum for the Clyde Dam, New Zealand (the mean 10,000 yr, ka, return period response spectrum) is developed in accordance with official guidelines and utilizes constraints provided by seven precariously balanced rocks (PBRs) located 2 km from the dam site and the local active Dunstan fault. The PBRs are located in the hanging wall of the fault. Deterministic PBR fragilities are estimated from field measurements of rock geometries and are the dynamic peak ground accelerations (PGAs) required for toppling. PBR fragility ages are modeled from 10Be cosmogenic isotope exposure dating techniques and are in the range of 24-66 ka. The fragility ages are consistent with the PBRs having survived at least two large Dunstan fault earthquakes. We develop a PGA-based fragility distribution from all of the PBRs, which represents the cumulative toppling probability of a theoretical random PBR as a function of PGA. The fragility distribution is then used to eliminate logic-tree branches that produce PGA hazard curves that would topple the random PBR with a greater than 95% probability (i.e., less than 5% survival probability) over a time period of 24 ka (youngest PBR fragility age). The mean 10 ka spectrum of the remaining hazard estimates is then recommended as the SEE spectrum for the dam site. This SEE spectrum has a PGA of 0.55g, which is significantly reduced from the 0.96g obtained for a preliminary version of the SEE spectrum. The reduction is due to the combined effects of the PBR constraints and a substantial update of the probabilistic seismic hazard model. The study serves as an important proof-of-concept for future applications of FGFs in engineering design. [ABSTRACT FROM AUTHOR]

Elastic rebound theory forms the basis of the standard earthquake cycle model and predicts large earthquakes to recur regularly through cycles of strain accumulation and release. Yet few individual earthquake records are sufficiently long to test the theory. Here we characterize the distribution of earthquake interevent times from a global compilation of 80 long‐term records. We find that large earthquakes recur more regularly than a random Poisson process on individual fault segments. The majority of Earth's well‐studied faults shows weakly periodic and uncorrelated large earthquake recurrence, consistent with the expectations of elastic rebound theory. However, many low activity‐rate (annual occurrence rates < 2 × 10−4) faults show random or clustered earthquake recurrence, which cannot be explained by elastic rebound theory. Plain Language Summary: To help society prepare for earthquakes, we use the record of previous earthquakes to forecast the chance of future large earthquakes. A key question is whether large earthquakes on a particular fault recur regularly, randomly, or cluster together in time. Here we compile records from 80 different studies of prehistoric earthquakes. We show that large earthquakes on a particular fault recur more regularly than random, except in regions that experience few earthquakes. This means that for regions that experience many earthquakes, we can forecast future large earthquake occurrence with some degree of skill. In contrast, forecasting large earthquake occurrence in places that experience few earthquakes, and where we expect them least, remains exceptionally difficult. Key Points: We characterize the distribution of earthquake interevent times from a global compilation of 80 long‐term recordsMost active faults show weakly periodic recurrence of large earthquakes consistent with elastic rebound theoryFaults in slowly deforming regions have highly variable earthquake interevent times [ABSTRACT FROM AUTHOR]

The loss of life and economic consequences caused by several recent earthquakes demonstrate the importance of developing seismically safe building codes. The quantification of seismic hazard, which describes the likelihood of earthquake-induced ground shaking at a site for a specific time period, is a key component of a building code, as it helps ensure that structures are designed to withstand the ground shaking caused by a potential earthquake. Geologic or geomorphic data represent important inputs to the most common seismic hazard model (probabilistic seismic hazard analyses, or PSHAs), as they can characterize the magnitudes, locations, and types of earthquakes that occur over long intervals (thousands of years). However, several recent earthquakes and a growing body of work challenge many of our previous assumptions about the characteristics of active faults and their rupture behavior, and these complexities can be challenging to accurately represent in PSHA. Here, we discuss several of the outstanding challenges surrounding geologic and geomorphic data sets frequently used in PSHA. The topics we discuss include how to utilize paleoseismic records in fault slip rate estimates, understanding and modeling earthquake recurrence and fault complexity, the development and use of fault-scaling relationships, and characterizing enigmatic faults using topography. Making headway in these areas will likely require advancements in our understanding of the fundamental science behind processes such as fault triggering, complex rupture, earthquake clustering, and fault scaling. Progress in these topics will be important if we wish to accurately capture earthquake behavior in a variety of settings using PSHA in the future. Plain Language Summary Growing infrastructure and increasing population have caused significant loss of life due to recent large earthquakes, with the 2008 Mw 7.9Wenchuan and 2005 Mw 7.6 Kashmir earthquakes each causing greater than 50,000 deaths. These earthquakes highlight the need for the development of building codes designed to withstand the strong ground shaking caused by earthquakes, as reinforced infrastructure is one of the most important factors for preventing fatalities due to ground shaking from earthquakes. Identifying the seismic hazard of a region, or the likelihood of ground shaking at a site due to potential earthquakes over time, is a key ingredient for informing a defensible building code. Here, we focus on current and future advances in how data from the fields of geology and geomorphology contribute to the most widely used type of seismic hazard model. These geologic data represent vital components to seismic hazard models, as they can provide information about the location and types of earthquakes that can occur over long, thousands of years, time periods, that cannot be obtained using other methods.We discuss some of the most pressing scientific issues about these data that are important for the development of seismic hazard models and defensible building codes. [ABSTRACT FROM AUTHOR]

We analyse seismic data collected from a short-term array deployment in the low seismicity area of Dunedin city, New Zealand. The addition of this temporary network to the permanent GeoNet national seismic network allows detection of earthquakes not captured by the GeoNet network. Using one of the newly detected earthquakes as a master event, we employ a template match-filter analysis to identify similar events in the area. Specifically, we record a cluster of micro-events at the northern extent of the Akatore Fault (<15 km from the city centre). A recent paleoseismic study has shown the Akatore Fault to have had multiple earthquake ruptures in the late Holocene after over 110 ka of quiescence, so the observed microseismicity is consistent with the fault being in a state of elevated activity. In contrast, other known faults in the area are quiescent with respect to both microseismicity and Holocene ruptures. The establishment of a permanent seismic array in and around Dunedin for the monitoring of microseismicity on the Akatore Fault and other local faults is warranted. [ABSTRACT FROM AUTHOR]

We present the results of a paleoseismic study of the Akatore Fault in the low seismicity region of Otago, New Zealand. Two trenches reveal at least three reverse fault ruptures that are constrained to have occurred between 13,314 B.C. and 680 A.D. (antepenultimate event), 737 and 960 A.D. (penultimate event) and 1047 and 1278 A.D. (most recent event), with a single-event displacements of 1.6–2.5 m. Ground Penetrating Radar (GPR) profiles and sediment analyses show that a 125 ka marine terrace is likely also only displaced by these three events, suggesting these earthquakes have ended a minimum 110,000 year period of quiescence on the fault. The fault therefore appears to exhibit strong aperiodicity of earthquake occurrence, a characteristic previously suggested for the Akatore Fault and other well-studied Otago faults. Slip rate and recurrence interval for the current active period are 0.3–6.0 mm/yr and 450–5110 years respectively. We suggest that for seismic hazard assessments in nearby Dunedin it is prudent to assume that the high rates of recent earthquakes will continue into the immediate future on the Akatore Fault. [ABSTRACT FROM AUTHOR]

Areas that experience permanent ground deformation in earthquakes (e.g., surface fault rupture, slope failure, and/or liquefaction) typically sustain greater damage and loss compared to areas that experience strong ground shaking alone. The 2016 Mw 7.8 Kaikoura earthquake generated ≥220 km of surface fault rupture. The amount and style of surface rupture deformation varied considerably, ranging from centimetre-scale distributed folding to metre-scale discrete rupture. About a dozen buildings - mainly residential (or residential-type) structures comprising single-storey timber-framed houses, barns and wool sheds with lightweight roofing material - were directly impacted by surface fault rupture with the severity of damage correlating with both local discrete fault displacement and local strain. However, none of these buildings collapsed. This included a house built directly atop a discrete rupture that experienced ~10 m of lateral offset. The foundation and flooring system of this structure allowed decoupling of much of the ground deformation from the superstructure thus preventing collapse. Nevertheless, buildings directly impacted by surface faulting suffered greater damage than comparable structures immediately outside the zone of surface rupture deformation. From a life-safety standpoint, all these buildings performed satisfactorily and provide insight into construction styles that could be employed to facilitate non-collapse performance resulting from surface fault rupture and, in certain instances, even post-event functionality. [ABSTRACT FROM AUTHOR]

The Hundalee fault is one of at least 20 faults that ruptured during the 2016 Mw 7.8 Kaikōura earthquake in the northeast of the South Island of New Zealand. Here, we document a 12 km onshore section of the Hundalee fault that exhibited surface rupture from this event. To the northeast of our observations, the fault crosses the coast, and independent seabed surveys show that the 2016 rupture continued at least 2 km offshore. No surface rupture was observed across the southwestern section of the Hundalee fault, which crosses hilly vegetated terrain and poorly consolidated valley floor sediment. However, previous Interferometric Synthetic Aperture Radar (InSAR) analyses suggest that a 9 km long section of the fault did rupture. Hence, the minimum length of the 2016 rupture along the Hundalee fault is 23 km. Field measurements indicate oblique dextral reverse slip along northeast trending Hundalee fault sections and reverse sinistral slip along north to north northeast trending sections. This is consistent with the regional principal horizontal shortening direction. Maximum vertical and horizontal offset measurements are 2.5±0.5 and 3.7±0.5 m, respectively. The discontinuous and irregular surface ruptures we observed are characteristic of a structurally immature fault, yet previous geological mapping indicates that the Hundalee fault is a regionally significant fault with >1 km late Cenozoic throw. Furthermore, a 60 m wide sequence of fault rocks exposed by the rupture indicates that slip has localized into <10 cm thick gouge zones, as anticipated for a mature fault. Therefore, a discrepancy exists between geological evidence of the Hundalee fault being a structurally mature fault and the characteristics of the 2016 rupture. We speculate that this signifies that the 2016 rupture was imposed on the Hundalee fault by movement across an inefficient multifault network rather than independent rupture of the Hundalee fault itself. [ABSTRACT FROM AUTHOR]

We compare the magnitudes of the 2016 Mw 7.8 Kaikōura and 2010 Mw 7.1 Darfield, New Zealand, earthquakes with the magnitudes estimated for the respective earthquake sources from recently published scaling relationships that provide estimates of magnitude as a function of slip rate in addition to rupture length (Anderson et al., 2017). In this test using data that were not considered when the model was developed, we find that these new relationships provide a range of magnitude estimates that are within 1.0 standard deviations of the observed magnitudes of the earthquakes (estimated Mw 7.75-8.03 vs. observed Mw 7.8±0.2 for Kaikōura and estimated Mw 7.17-7.28 vs. Mw 7.1±0.2 for Darfield). Although both earthquakes involved a complex rupture process (especially the Kaikōura earthquake) and the Darfield earthquake occurred on a previously unknown fault with a very long recurrence interval, the earthquake magnitudes are consistent with the Anderson et al. (2017) models. Thus, we consider the new scaling relationships for strike-slip earthquakes to be suitable candidates for use in seismic hazard source model developments in New Zealand while acknowledging that the evaluation is based on just two major earthquakes. We expect the scaling relationships to be part of the ensemble of inputs to the next version of the national seismic hazard model for New Zealand, which will be applied to myriads of applications in engineering, planning, and risk analysis. [ABSTRACT FROM AUTHOR]

Multiple (>20) crustal faults ruptured to the ground surface and seafloor in the 14 November 2016 Mw 7.8 Kaikōura earthquake, and many have been documented in detail, providing an opportunity to understand the factors controlling multifault ruptures, including the role of the subduction interface. We present a summary of the surface ruptures, as well as previous knowledge including paleoseismic data, and use these data and a 3D geological model to calculate cumulative geological moment magnitudes (MGw) and seismic moments for comparison with those from geophysical datasets. The earthquake ruptured faults with a wide range of orientations, sense of movement, slip rates, and recurrence intervals, and crossed a tectonic domain boundary, the Hope fault. The maximum net surface displacement was ~12 m on the Kekerengu and the Papatea faults, and average displacements for the major faults were 0.7-1.5 m south of the Hope fault, and 5.5-6.4 m to the north. MGw using two different methods are MGw7.7+0.3-0.2 and the seismic moment is 33%-67% of geophysical datasets. However, these are minimum values and a best estimate MGw incorporating probable larger slip at depth, a 20 km seismogenic depth, and likely listric geometry is MGw7.8±0.2, suggests ≤32% of the moment may be attributed to slip on the subduction interface and/or a midcrustal detachment. Likely factors contributing to multifault rupture in the Kaikōura earthquake include (1) the presence of the subduction interface, (2) physical linkages between faults, (3) rupture of geologically immature faults in the south, and (4) inherited geological structure. The estimated recurrence interval for the Kaikōura earthquake is ≥5,000-10,000 yrs, and so it is a relatively rare event. Nevertheless, these findings support the need for continued advances in seismic hazard modeling to ensure that they incorporate multifault ruptures that cross tectonic domain boundaries. [ABSTRACT FROM AUTHOR]

We construct magnitude-frequency distributions according to the Gutenberg-Richter (GR) relation for four major active fault earthquake sources used in previous seismic hazard assessments of New Zealand, and evaluate if GR-based fault models can be considered for future probabilistic seismic hazard analysis (PSHA). Ultimately, we aim to understand whether GR-based fault models can be used with the characteristic earthquake model, or if they should be removed from consideration. Our GR magnitude-frequency distributions are constructed for the fault sources using constraints from historical earthquakes, paleoseismic data, and assumptions of earthquake clustering. We find that when the resulting distributions are applied to a model that assumes earthquakes are random and independent in time (as in typical PSHA), the model predicts (1) rates of the largest earthquakes that are less than the rates of equivalent earthquakes derived from paleoseismic data, but cannot be ruled out due to the large uncertainties in data and analysis, and (2) rates of Mw≥5 earthquakes that are considerably greater than the observed Mw≥5 rates. We also undertake epidemic-type aftershock sequence (ETAS) simulations to determine the potential range of magnitude and frequency that could be expected due to earthquake clustering. We find that the simulations show compatibility between the GR relation and the available constraints for each fault source, which suggests that the GR relation cannot be ruled out as a source of plausible description of the magnitude-frequency distribution for the fault sources. The mixed results of our analysis suggest that including both GR and characteristic earthquake models in PSHA is an appropriate approach at this stage. Although the simultaneous implementation of both models is commonplace in PSHA, we can now justify doing so on the basis of this analysis. Considerations as to the return period of interest in PSHA and the scale dependency of magnitude-frequency distributions may further guide the use of the two models. [ABSTRACT FROM AUTHOR]

We provide a summary of the surface fault ruptures produced by the Mw7.8 14 November 2016 Kaikōura earthquake, including examples of damage to engineered structures, transportation networks and farming infrastructure produced by direct fault surface rupture displacement. We also provide an overview of the earthquake in the context of the earthquake source model and estimated ground motions from the current (2010) version of the National Seismic Hazard Model (NSHM) for New Zealand. A total of 21 faults ruptured along a c.180 km long zone during the earthquake, including some that were unknown prior to the event. The 2010 version of the NSHM had considered multi-fault ruptures in the Kaikōura area, but not to the degree observed in the earthquake. The number of faults involved a combination of known and unknown faults, a mix of complete and partial ruptures of the known faults, and the non-involvement of a major fault within the rupture zone (i.e. the Hope Fault) makes this rupture an unusually complex event by world standards. However, the strong ground motions of the earthquake are consistent with the high hazard of the Kaikōura area shown in maps produced from the NSHM. [ABSTRACT FROM AUTHOR]

We combine geological and seismological data to describe the shape of the magnitude-frequency distribution for the Canterbury earthquake sequence. In doing so, we take the opportunity of the new datasets to address a long-standing debate in the literature as to whether the seismicity of individual faults or fault zones is best described by the Gutenberg-Richter (GR) relationship or the characteristic earthquake (CE) model. We find that the magnitude-frequency distribution for the entire composite fault zone of the Canterbury earthquake sequence is adequately described by the GR relationship when uncertainties in the GR curve (fitted to the instrumental catalog data) and the range of paleoseismically derived recurrence intervals for large (mainshock) earthquakes on the Greendale fault are collectively considered. In contrast, the magnitude-frequency distribution for the smaller area of the Greendale fault is better described by the CE model. The difference is one of scale, in that the composite fault zone represented by the Canterbury earthquake sequence shows a GR distribution, whereas individual faults within the zone show CE distributions. Definition of magnitude-frequency distributions for seismic-hazard modeling must therefore take scaling considerations into account, rather than simply assuming that a single magnitude-frequency distribution shape is applicable to all fault definitions. [ABSTRACT FROM AUTHOR]

We use new paleoseismic data and lidar to reassess late Quaternary activity of the NW (northwest) Cardrona Fault, a ∼60 km long range-bounding fault in Otago. Paleoseismic investigations of the NW Cardrona Fault were conducted in the 1980s, but findings were limited by a paucity of materials suitable for dating. Here, re-exposure and re-assessment of a 1980s trench at Macdonalds Creek provide stratigraphic evidence for two surface rupturing earthquakes on the NW Cardrona Fault. Through Optically Stimulated Luminescence dating and OxCal modelling, we estimate these earthquakes occurred at (mean ± 2 standard deviations, σ) 20.5 ± 7.8 ka and 8.7 ± 6.6 ka. The timings of these earthquakes are consistent with those proposed from re-interpretation of another 1980s trench on the NW Cardrona Fault in the Kawarau River valley, ∼25 km farther south. The slip rate and recurrence interval derived from the Macdonalds Creek trench data are 0.13 ± 0.05 mm/yr and 11,800 ± 5100 years (2σ error) respectively. These estimates imply lower slip rates and longer earthquake recurrence intervals on the NW Cardrona Fault than previously assessed. [ABSTRACT FROM AUTHOR]

We provide estimates of the rates of natural modification of badlands pinnacles formed in soft sediments at two sites in New Zealand and assess the utility of pinnacles for constraining seismic-hazard models. One of the sites is in a humid temperate environment, and the other is in a semiarid environment. Rates of pinnacle modification of 30-270 mm/yr (equivalent to 3-27 m/century) are estimated by comparison of images acquired one-to-two decades apart. The primary mode of modification is the progressive narrowing of the pinnacle column by precipitationinduced erosion, along with consequent loss of height as the columns become thin and unstable. Additional damage may have been produced by earthquake shaking for specific pinnacles, but in general this is likely to be trivial, given that (1) estimates of the levels of peak ground acceleration (PGA) required to shake down the pinnacles at the two sites are at least a factor of 5-13 greater than the PGAs predicted or measured from regional earthquakes during the time periods of observation (in other words they would only be significantly damaged by major local earthquakes) and (2) a fragile pinnacle has actually formed in the time periods of observation. The pinnacle modification rates are rapid enough that they would not have existed oneto- two centuries ago or would have been of substantially different geometries. As such, pinnacles are unlikely to be useful for constraining seismic-hazard models for return periods greater than a few decades, at least in the context of the New Zealand environment. [ABSTRACT FROM AUTHOR]

New time-dependent seismicity models for the Christchurch region reflect the greatly enhanced seismicity in the region at present, and the gradual decrease of the seismicity over the next few decades. These seismicity models, along with modified ground-motion prediction equations and revised hazard calculation procedures have been used to derive new seismic hazard estimates for timeframes from months to 50 years. The hazard estimates have been used for a variety of applications crucial to planning and implementing the recovery of Christchurch. The new model includes higher amplitude spectra for designing new structures and assessing existing ones, magnitude-weighted peak ground acceleration hazard curves that account for duration effects for liquefaction assessment and remediation, and peak ground acceleration curves for evaluating the probabilities of rock falls. Particularly challenging has been the incorporation of time-varying hazard components into the redesign levels. [ABSTRACT FROM AUTHOR]

A fundamentally important but typically abbreviated component of seismic-hazard analysis is the selection of earthquake scaling relationships. These are typically regressions of historical earthquake datasets, in which magnitude is estimated from parameters such as fault rupture length and area. The mix of historical data from different tectonic environments and the different forms of the regression equations can result in large differences in magnitude estimates for a given fault rupture length or area. We compile a worldwide set of regressions and make a first-order shortlisting of regressions according to their relevance to a range of tectonic regimes (plate tectonic setting and fault slip type) in existence around the world. Regression relevance is based largely on the geographical distribution, age, and quantity/quality of earthquake data used to develop them. Our compilation is limited to regressions of magnitude (or seismic moment) on fault rupture area or length, and our shortlisted regressions show a large magnitude range (up to a full magnitude unit) for a given rupture length or area across the various tectonic regimes. These large differences in magnitude estimates underline the importance of choosing regressions carefully for seismic-hazard application in different tectonic environments. [ABSTRACT FROM AUTHOR]

Known earthquake sources include mapped active faults and locations where historical earthquakes have occurred. We propose a long-term earthquake likelihood model that makes use of both types of sources but does not invoke the concepts of fault segmentation or characteristic earthquakes. The model has two components, one based on proximity to the locations of past earthquakes, taking into account their magnitudes, and another based on proximity to mapped faults, taking into account their slip rates. The Gutenberg-Richter law is invoked for earthquake magnitudes and an inverse power law for the diminution of earthquake rate density with distance from past earthquakes and mapped faults. The model is applied to the New Zealand region using the National Seismic Hazard Model fault-source model and the earthquake catalog since 1951. The parameters of each component are optimized for the period 1987-1996, and the rate density of the combined model is estimated as an optimal linear combination of the two components. In a test on the independent period from 1997-2006, the combined model has an information gain (log-likelihood increase) per earthquake of about 0.1 over each of the component models. The model is also optimized over the longer period 1987-2006 for comparison with other long-term models in the New Zealand Earthquake Forecast Testing Centre. [ABSTRACT FROM AUTHOR]

This article presents results from the consideration of epistemic uncertainties in New Zealand (NZ) probabilistic seismic-hazard analysis. Uncertainties in ground-motion prediction are accounted for via multiple ground-motion prediction equations within the logic-tree framework. Uncertainties in the fault-based seismicity of the earthquake rupture forecast due to uncertainties in fault geometry, slip parameters, and magnitude-scaling relationships are considered in a Monte Carlo simulation framework. Because of the present lack of fault-specific data quantifying uncertainties for many faults in NZ, representative values based on judgement and available data for NZ and foreign faults were utilized. Uncertainties in the modelling of background seismicity were not considered. The implications of the considered epistemic uncertainties in terms of earthquake magnitude-frequency distributions and probabilistic seismic-hazard analyses for two spectral acceleration ordinates, two soil classes, and two locations (Wellington and Christchurch) are examined. The results illustrate that, for the uncertainties considered, the variation in seismic hazard due to the adopted ground-motion prediction model is larger than that due to the uncertainties in the earthquake rupture forecast. Of the earthquake rupture forecast uncertainties considered, the magnitude-geometry scaling relationships was the most significant, followed by fault rupture length. Hence, the obtained results provide useful guidance on which modelling issues are the most critical in the reliability of seismic-hazard analyses for locations in NZ. [ABSTRACT FROM AUTHOR]

A team of earthquake geologists, seismologists, and engineering seismologists has collectively produced an update of the national probabilistic seismic hazard (PSH) model for New Zealand (National Seismic Hazard Model, or NSHM). The new NSHM supersedes the earlier NSHM published in 2002 and used as the hazard basis for the New Zealand Loadings Standard and numerous other end-user applications. The new NSHM incorporates a fault source model that has been updated with over 200 new onshore and offshore fault sources and utilizes new New Zealand-based and international scaling relationships for the parameterization of the faults. The distributed seismicity model has also been updated to include post-1997 seismicity data, a new seismicity regionalization, and improved methodology for calculation of the seismicity parameters. Probabilistic seismic hazard maps produced from the new NSHM show a similar pattern of hazard to the earlier model at the national scale, but there are some significant reductions and increases in hazard at the regional scale. The national-scale differences between the new and earlier NSHM appear less than those seen between much earlier national models, indicating that some degree of consistency has been achieved in the national-scale pattern of hazard estimates, at least for return periods of 475 years and greater. [ABSTRACT FROM AUTHOR]

Potentially active faults are exposed in the steep glaciated topography of the central Southern Alps, New Zealand, immediately adjacent to the Alpine Fault plate boundary. Four major faults exposed along the flanks of three of the highest mountain ranges strike 10-23 km (potentially 40 km) NNE oblique to the Alpine Fault, dipping 57° ± 12° NW in the opposite direction. Youngest discernable motions were reverse dip-slip, accommodating both margin-perpendicular shortening and dextral margin-parallel components of plate motion. Kinematic analysis yields a compression axis (295/10° ± 9° trend or plunge) equivalent to the contemporary shortening determined from seismological and geodetic studies, suggesting the faults may be active, although definitive evidence for recent movement or single event displacements is lacking. There are 106 other potentially active faults mapped in central Southern Alps with strike lengths 4-73 km. Earthquake parameters were assigned from fault trace lengths and historical earthquake statistics, indicating potential for MW 5.5-7.4 earthquakes at recurrence intervals of 1000-10,000 years. Such long recurrence intervals are consistent with the faults having little surface expression, with rapid erosion of these seismically agitated mountains erasing any evidence of surface rupture during periods between earthquakes. The central Southern Alps faults exemplify the difficulty in fully deciphering long-term (e.g., Holocene or Quaternary) records of seismicity in tectonically active regions with rapidly evolving landscapes. Although there may be little evidence of surface ruptures remaining in the landscape, the faults are still an important potential source of earthquakes and seismic hazard. [ABSTRACT FROM AUTHOR]

Wepresentapreliminary probabilistic seismic hazard analysis (PSHA)of a site in the Otway basin, Victoria, Australia, as part of the CO2CRC Otway Project for CO2 storage risk. The study involves estimating the likelihood of future strong earthquake shaking at the site and utilizes three datasets: (1) active faults, (2) historical seismicity, and (3) geodetic surface velocities. Our analysis of geodetic data reveals strain rates at the limit of detectability and not significantly different from zero. Consequently, we do not develop a geodetic-based source model for this Otway model. We construct logic trees to capture epistemic uncertainty in both the fault and seismicity source parameters and in the ground-motion prediction. A new feature for seismic hazard modeling in Australia, and rarely dealt with in low-seismicity regions elsewhere, is the treatment of fault episodicity (long-term activity versus inactivity) in our Otway model. Seismic hazard curves for the combined (fault and distributed seismicity) source model show that hazard is generally low, with peak ground acceleration estimates of less than 0.1 g at annual probabilities of 10-3 10-4/yr. Our preliminary analysis therefore indicates that the site is exposed to a low seismic hazard that is consistent with the intraplate tectonic setting of the region and unlikely to pose a significant hazard for CO2 containment and infrastructure. [ABSTRACT FROM AUTHOR]

We develop a testing methodology for the New Zealand national probabilistic seismic hazard (PSH) model that builds on the groundwork of previous studies. Our fundamental approach is to test the full model, or in other words, the final output of the model (ground-motion exceedance for a given return period). Our results show that the PSH model is rejected as underpredicting the historical number of exceedances for specific peak ground acceleration (PGA) levels obtained directly from instrumental strong-motion data over the last 1-4 decades. However, when aftershock ground motions are removed from the strong-motion data, the model is not inconsistent with the observations. The implications for the PSH model are that the lack of aftershocks in the model led to initial model rejection and that the model may perform better for short (decadal) time periods if aftershocks are included in the PSH model. The results are different from those of earlier Modified Mercalli Intensity (MMl)-based studies that suggested the PSH model was predicting hazard slightly higher than that of the historical record. Our new test dataset has the advantage of using observed PGA rather than PGA inferred from MMI. Establishment of a protocol for formally testing future versions of the New Zealand PSH model within a testing center such as those using the Collaboratory for the Study of Earthquake Predictability protocol will require consideration of the fact that the tests are limited by the available datasets of strong earthquake shaking. [ABSTRACT FROM AUTHOR]

We determine minimum exposure ages for unstable outcrops at three sites in Amargosa Desert, southwestern Nevada, including a site at the southern end of Yucca Mountain. Varnish microlamination dating techniques provide minimum exposure ages of 12.5-36 k.y. for the unstable outcrops of welded tuff, including a 24 k.y. age for the south Yucca Mountain site. The youngest exposure age (12.5 k.y.) is found at the site located only 10 km from the Death Valley-Furnace Creek fault, suggesting outcrops may be more frequently modified when close to major active earthquake sources. A simplistic stability assessment of the south Yucca Mountain outcrops suggests peak ground accelerations (PGAs) may not have exceeded about 1g (uncertainty bounds 0.5-2g) in at least 24 k.y. A PGA of 1g is consistent with the predicted 24 k.y. return period PGAs from the near decade-old Yucca Mountain probabilistic seismic hazard (PSH) model, except for the ninety-fifth percentile and above. We gain confidence in our interpretations by additionally observing: (1) minimal damage to the south Yucca Mountain outcrops from a recent moderate earthquake that is estimated to have produced a PGA of less than 0.1g there (i.e., motions less than 0.5g do not significantly damage the outcrops); and (2) severe damage to similar volcanic outcrops associated with PGAs of the order 0.5-1g near a nuclear blast site from the 1960s. These observations support our suggestion that PGAs greater than 0.5-1g have not occurred at the south Yucca Mountain site for a time period of at least 24 k.y. Significant seismic events that substantially modify the outcrops and produce associated rubble fields may therefore occur on longer time scales. [ABSTRACT FROM AUTHOR]

The possibility that a moderate earthquake may be followed by an equal or larger one (foreshock probability) increases the hazard in its immediate vicinity for a short time by an order of magnitude or more. Thus, foreshock probabilities are of interest for time-dependent seismic hazard forecasts. We calculate the probability of an initial earthquake (a foreshock) being followed by a mainshock in New Zealand, considering the parameters of elapsed time and distance and magnitude differences between foreshock and mainshock. We use nonaftershock events between 1964 and 2007, with magnitude =4:0 and shallower than 40 km, separating the catalog into events within and outside the Taupo volcanic zone (TVZ). We provide a model for the probability P(t, r, δM) that at time t after a potential foreshock (FS) of magnitude MFS and at distance r, a mainshock with magnitude MFS + δM will occur: P(t, r, δM) = P0 x 10(-BδM)(t + ct)-pt(r + cr)-pr , where P0, B, pt, ct, pr, and cr are constants to be determined. We find that (1) binning data using fixed intervals of time or space before fitting the parameters returns different values than a more robust approach of fitting directly the entire range, (2) foreshock probabilities decrease with increasing interevent time as described by a modified Omori law with an exponent pt close to 1 (0.9 7plusmn; 0.2 [TVZ] and 0.8 ± 0.1 elsewhere--uncertainty estimates are 95% confidence intervals throughout this study), (3) foreshock probabilities decrease with increasing epicentral distance also following a modified Omori type decay with exponent pr of 0.9 7plusmn; 0.2 (non-TVZ) and 1.7 ± 0.6 (TVZ), and (4) the mainshock magnitude distribution follows the Gutenberg--Richter relationship (B = 1.0 ± 0.17 [non-TVZ] and 1.5 ± 0.5 [TVZ]). The differences between the TVZ and the rest of New Zealand are consistent with higher attenuation in the region, deduced from previous studies. [ABSTRACT FROM AUTHOR]

We compare the historical record of earthquake hazard experienced at 78 towns and cities (sites) distributed across New Zealand and the continental United States with the hazard estimated from the national probabilistic seismic-hazard (PSH) models for the two countries. The two PSH models are constructed with similar methodologies and data. Our comparisons show a tendency for the PSH models to slightly exceed the historical hazard in New Zealand and westernmost continental United States interplate regions, but show lower hazard than that of the historical record in the continental United States intraplate region. Factors such as non-Poissonian behavior, parameterization of active fault data in the PSH calculations, and uncertainties in estimation of ground-motion levels from historical felt intensity data for the interplate regions may have led to the higher-than-historical levels of hazard at the interplate sites. In contrast, the less-than-historical hazard for the remaining continental United States (intraplate) sites may be largely due to site conditions not having been considered at the intraplate sites, and uncertainties in correlating ground-motion levels to historical felt intensities. The study also highlights the importance of evaluating PSH models at more than one region, because the conclusions reached on the basis of a solely interplate or intraplate study would be very different. [ABSTRACT FROM AUTHOR]

We undertake the first New Zealand-based pilot study to investigate the use of ancient precariously balanced rocks (rocks that are unstably balanced on top of a pedestal) as a criteria for testing estimates of earthquake shaking from probabilistic seismic hazard models for long-return periods. To date, research to test seismic-hazard models in New Zealand has been restricted to the short historical record of earthquakes. Our survey of five sites in the South Island of New Zealand has yielded a total of 28 precariously balanced rocks which, on the basis of established methodology, are used to provide estimates of the maximum ground motions that could have occurred at the sites since the rocks became precarious. Age estimates for the precariously balanced rocks (40,400 to 55.300 years for central Otago schist rocks, and 77,300 years for northwest Nelson granitic rocks) are made from a limited number of cosmogenic dates obtained from bedrock removed from the pedestals of the rocks. Comparisons of the maximum peak ground accelerations and ages of the precariously balanced rocks with seismic-hazard curves derived from the New Zealand national seismic-hazard model show that the rocks indicate considerably lower hazard than the seismic-hazard model at sites located within 5 km of active faults, whereas the agreement is favorable for sites located away from active faults. The variability about the median estimates of peak ground acceleration for the fault sources and/or the median accelerations for the fault sources assumed in the seismic-hazard model may therefore be overestimated for the sites near active faults. [ABSTRACT FROM AUTHOR]

Three trenches excavated across the central portion of the right-lateral strike-slip Wairau Fault in South Island, New Zealand, exposed a complex set of fault strands that have displaced a sequence of late Holocene alluvial and colluvial deposits. Abundant charcoal fragments provide age control for various stratigraphic horizons dating back to c. 5610 yr ago. Faulting relations from the Wadsworth trench show that the most recent surface rupture event occurred at least 1290 yr and at most 2740 yr ago. Drowned trees in landslide-dammed Lake Chalice, in combination with charcoal from the base of an unfaulted colluvial wedge at Wadsworth trench, suggest a narrower time bracket for this event of 1811-2301 cal. yr BP. The penultimate faulting event occurred between c. 2370 and 3380 yr, and possibly near 2680 ± 60 cal. yr BP, when data from both the Wadsworth and Dillon trenches are combined. Two older events have been recognised from Dillon trench but remain poorly dated. A probable elapsed time of at least 1811 yr since the last surface rupture, and an average slip rate estimate for the Wairau Fault of 3-5 mm/yr, suggests that at least 5.4 m and up to 11.5 m of elastic shear strain has accumulated since the last rupture. This is near to or greater than the single-event displacement estimates of 5-7 m. The average recurrence interval for surface rupture of the fault determined from the trench data is 1150-1400 yr. Although the uncertainties in the timing of faulting events and variability in inter-event times remain high, the time elapsed since the last event is in the order of 1-2 times the average recurrence interval, implying that the Wairau Fault is near the end of its interseismic period. [ABSTRACT FROM AUTHOR]