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This is the second of a two-part New Zealand Journal of Geology and Geophysics Special Issue on understanding sedimentary systems in Aotearoa-New Zealand's Hikurangi Subduction Margin (HSM). This volume includes six research papers that explore sediment-tectonic interactions operating over a range of spatio-temporal scales. We take a distinctive perspective moving from the subduction deformation front in the Hikurangi Trough, upslope to the subduction wedge, and onshore to the Coastal Ranges. Temporally, papers span the onset of subduction in the Miocene, to disentangling provenance of turbidity currents triggered by the 2016 CE Kaikōura Earthquake. Collectively, the studies in the special issue reveal a complicated and continually evolving margin, where active tectonics and volcanism, coupled with vigorous climatic and oceanographic drivers, modulate erosion, transport, and depositional cycles of vast volumes of terrigenous sediment into ocean basins. Despite decades of significant research advances in our knowledge of the HSM, considerable scope remains for future work. A deeper understanding of fundamental tectonic-sediment interactions operating on active margins, along with the significant geohazards they pose remain outstanding research needs. Collectively, Volumes 1 and 2 highlight enduring interest in the HSM as a globally important natural laboratory for the study of subduction zone geoscience. [ABSTRACT FROM AUTHOR]

The 2016 Mw 7.8 Kaikōura Earthquake triggered simultaneous turbidity currents down ten submarine canyons along a 200 km stretch of the continental slope, east of New Zealand. Some discharged into the Hikurangi Channel which flows >1500 km northwards along the abyssal trench floor. To better understand provenance continuity in deep-sea sedimentary records, foraminiferal samples from the 2016 turbidites from 17 canyon and channel cores were used to investigate the source histories of these submarine gravity flows. Cluster analyses suggest the canyon provenances for most 2016 turbidite faunas should be determinable using a combination of the relative abundance of key benthic genera, planktic foraminiferal index (dissolution), absolute test abundance and planktic % of the foraminiferal faunas. Two ordinations (PCA, PCO) based on these parameters were used to infer provenance and flow history. One hundred kilometres down the Hikurangi Channel, faunas in the 2016 turbidite confirm a Kaikōura Canyon source. Further downstream, 200–500 km north of the confluence with Campbell, Cook and Opouawe canyons, faunas indicate that the 2016 turbidite in the northern Hikurangi Channel is a composite deposit, from an initial Opouawe-Cook canyon-sourced turbidity current over-ridden and partly mixed with, a Kaikōura Canyon-sourced flow that arrived sometime later. [ABSTRACT FROM AUTHOR]

To gain new insights into ground-motion phenomena in New Zealand (NZ), we apply the non-parametric generalized inversion technique (GIT) in the Fourier domain to isolate the systematic source, path, and site effects from 20 813 seismograms, recorded by 693 sensors at 439 unique locations, from 1200 shallow crustal events (M w > 3) during the period 2000–2021. From the inverted source spectra, we derive Brune's stress parameter, ∆σ , which is found to follow a lognormal distribution with a log10 standard deviation of 0.36 or equivalently 0.83 in natural log unit. ∆σ slightly increases with focal depth and is practically independent of earthquake size (i.e. self-similar), but displays a statistically significant spatial clustering. Based on the inverted attenuation, a trilinear geometric-spreading function, and a distance-dependent quality-factor Q (f) model are found to well describe the attenuation in NZ; though a single |$Q(f)$| model is also obtained for the whole distance range: |$Q(f) = 149.1{f}^{0.62}$|⁠. Using the site response decomposed from GIT, we find that the soil classification scheme specified in NZ seismic code, NZS1170.5, has a limited capability in discerning the site-specific frequency-dependent amplification functions in comparison to a non-parametric clustering with the same number of discrete classes. The potential use of the spatial variation in source parameters from this GIT analysis in region-specific physics-based simulations is discussed. [ABSTRACT FROM AUTHOR]

Prehistoric records of subduction earthquakes are often distinguished by evidence of synchronous widespread coastal deformation, the extent of which negates the plausibility of alternative source faults. At the Hi-kurangi subduction margin in New Zealand, untangling the record of subduction interface ruptures is complicated. Large earthquake age uncertainties inhibit unique solutions of along-strike correlations, and complex patterns of coastal deformation caused by upper-plate faulting prevent reliable indication of source faults. In this work, we improved paleoearthquake reconstructions on the central Hikurangi margin with a new, well-constrained 5000 yr earthquake record from Pakuratahi Valley near Napier, North Island, New Zealand. Evidence of laterally extensive paleoenvironmental changes is consistent with coseismic subsidence and coseismic uplift in large earthquakes. Radiocarbon dates on fragile terrestrial macrofossils and tephra isochrons were used to construct robust age models that yielded earthquake ages of 4839-4601 calibrated (cal.) yr B.P., 3630-3564 cal. yr B.P., 2687-2439 cal. yr B.P., and 1228-823 cal. yr B.P. Integration of these ages with refined earthquake chronology from nearby Ahuriri Lagoon indicated that the next large earthquake impacting the Napier area is more likely to cause coastal subsidence than uplift. Drawing on correlations with cotemporal evidence elsewhere on the central margin, we infer that the overall patterns of coseismic deformation could be generated by either rupture of the subduction interface or upper-plate faults, or both. This inability to separate source faults for past earthquakes limits the efficiency of forecasting future earthquakes. Similar problems of intertwined paleoearthquake signatures likely apply to other plate boundaries, where we recommend cautious interpretation of coastal deformation to accurately address the hazard from both types of source faults. [ABSTRACT FROM AUTHOR]

Whakaari/White Island has been the most active New Zealand volcano in the 21st century, producing small phreatic and phreatomagmatic eruptions, which are hard to predict. The most recent eruption occurred in 2019, tragically claiming the lives of 22 individuals and causing numerous injuries. We employed shear‐wave splitting analyses to investigate variations in anisotropy between 2018 and 2020, during quiescence, unrest, and the eruption. We examined spatial and temporal variations in 3,499 shear‐wave splitting and 2,656 Vp/Vs ratio measurements. Comparing shear‐wave splitting parameters from similar earthquake paths across different times indicates that the observed temporal changes are unlikely to result from variations in earthquake paths through media with spatial variability. Instead, these changes may stem from variations in anisotropy over time, likely caused by changes in crack alignment due to stress or varying fluid content. Plain Language Summary: The most active volcano in New Zealand, known as Whakaari/White Island, has recently experienced numerous minor eruptions, which are hard to predict. The most recent eruption occurred in 2019, tragically claiming the lives of 22 individuals and causing multiple injuries. This study examines the stress field and characteristics of cracks within various parts of the volcano, during the period between 2018 and 2020. We used a method called shear‐wave splitting, which examines the alignment of cracks by measuring the speed of seismic waves in different orientations, and another method that measures the ratio of the speed of two different types of waves traveling through the medium (Vp/Vs). Our analysis revealed that both shear‐wave splitting and Vp/Vs changed over time in response to the variations in magmatic activity. This suggests that crack alignment, content, or numbers change in response to the stresses induced by magmatic activity at various depths within the volcano over time. Key Points: Background fast orientations were concentrated parallel to the crater wall at both measurement stationsSeismic waves that follow similar paths to the stations result in different fast orientations pre‐ and post‐eruptionVp/Vs ratio can provide valuable insights into the nature and evolution of seismic anisotropy in the Earth's interior [ABSTRACT FROM AUTHOR]

Large‐scale disturbance events provide ideal opportunities to directly study recolonisation processes in natural environments, via the removal of competitors and the formation of newly vacant habitat. A high magnitude earthquake in central New Zealand in 2016 created major ecological disturbance, with coastal tectonic uplift of up to ~ 6 m extirpating vast swathes of intertidal organisms. One of the affected species was Durvillaea antarctica (rimurapa or southern bull kelp), which is an important habitat‐forming intertidal macroalga capable of long‐distance dispersal. Across the complex fault system with varying amounts of uplift, the species was either locally extirpated or heavily reduced in abundance. We hypothesised that neutral priority effects and chance dispersal from other populations would influence which lineages would establish. We sampled individuals of D. antarctica across the uplift zone immediately after the earthquake in 2016 and then repeatedly sampled new recruits in the same areas between 2017 and 2020, using genotyping‐by‐sequencing to provide 'before' and 'after' genomic comparisons. Our results revealed strong geographic clustering but little evidence of new lineages establishing at disturbed sites, although populations at uplifted sites remain at remarkably low densities. We infer that recolonisation has thus far primarily originated from refugial, remnant patches within the uplift zone. To complement the phylogeographic analysis, we estimated oceanographic connectivity among the uplift zone sample locations. The connectivity modelling estimated that northbound dispersal of D. antarctica was more likely, but we have not yet detected southern genotypes in the recolonised populations. As the ongoing recolonisation process transitions from an ecological to an evolutionary timescale, change remains possible. This study provides the first genomic 'snapshots' of a natural recolonisation process following a large‐scale ecological disturbance event, and ongoing research has the potential to reveal important insight into both micro‐ and macroevolutionary processes. [ABSTRACT FROM AUTHOR]

New mapping of the Barberton Greenstone Belt in South Africa shows that the central part is a pseudo-stratigraphy made of shallow-water and deep-water siliciclastic and volcanic slide blocks, with individual blocks ranging in size from tens of meters to >10 km in length. The outcrop pattern and scale are remarkably similar to those of large-scale Miocene to recent submarine landslides in New Zealand along the active Hikurangi subduction zone that are periodically triggered by earthquakes on the subduction megathrust, providing evidence for megathrust earthquakes in the Paleoarchean. [ABSTRACT FROM AUTHOR]

Several studies suggest that large earthquakes (M > 7.0) can act as external triggers of volcanic unrest, and even eruption. This triggering is attributed to either ground shaking (dynamic stresses) or to permanent ground deformation (associated with static stress changes). However, large earthquakes are rare and testing triggering hypotheses has proven difficult. We use geodetic data to show that the 13 November 2016 Kaikōura earthquake (Mw 7.8) triggered local deformation of up to 11 mm at Taupō volcano, 500 km away, which lasted for approximately twelve days. Using elastic geodetic models, we infer that the observed deformation was caused by either aseismic fault slip or a dike intrusion. We then use strong motion data from the surrounding area to show that the Kaikōura earthquake caused maximum dynamic stress changes in the range of 0.15–0.9 MPa in the vicinity of Taupō volcano and conclude that these dynamic stress changes triggered local faulting or dike activity and the associated deformation at Taupō volcano. Plain Language Summary: It has often been proposed that large earthquakes can trigger volcanic eruptions. However, large earthquakes are rare and testing these triggering hypotheses is therefore difficult. We show that the 13 November 2016 Kaikōura earthquake triggered local ground movement at Taupō volcano, 500 km away, which lasted for approximately two weeks. We show that the observed ground movement was caused by either slow movement on a fault or by the movement of magma at depth. We then use seismology data from the surrounding area to show that the Kaikōura earthquake caused large pressure changes in the vicinity of Taupō volcano. We conclude that the ground shaking from the earthquake caused local faulting or magmatic activity and the associated ground movement at Taupō volcano. Key Points: The Mw7.8 Kaikōura earthquake was followed by local deformation at Taupō volcano, c. 500 km awayThe deformation observed is consistent with either a dike intrusion or aseismic slip on a faultDynamic stress changes in the range of 0.15–0.9 MPa caused by seismic waves from the Kaikōura earthquake triggered this response at Taupō [ABSTRACT FROM AUTHOR]

Ahi Tupua, the central section of the Taupō Volcanic Zone in the central North Island of New Zealand, encompasses Taupō and Ōkataina calderas and has been the most frequently active and productive silicic magma system worldwide during the Quaternary. The entire Taupō Volcanic Zone is underlain by the Hikurangi Subduction Zone where a Large Igneous Province, the Hikurangi Plateau, is being subducted, but Ahi Tupua exhibits much higher rates of magma output than either the northern or the southern sections. Trace element signatures of Ahi Tupua eruptive products suggest that both decompression melting and flux melting play a role in this rifted arc setting, with fluid flux signatures being more prevalent in regions of active caldera volcanism. Intermediate‐depth (50–300 km) earthquakes provide a means of studying faulting and fluid flow processes within and around the subducting slab beneath Ahi Tupua. Using data from the national seismic network and a 13‐station temporary network ("ECLIPSE"), we repick and relocate 397 intermediate‐depth earthquakes of magnitudes M2.5+ that occurred in a 29‐month interval, and compute focal mechanisms for a subset of 47 earthquakes. We observe some seismicity that may be within the mantle wedge but most of the relocated earthquakes occur within the crust and uppermost mantle of the subducted slab and exhibit a weak transition from predominantly normal‐faulting in the slab crust to predominantly reverse‐faulting in the slab mantle. No double seismic zone is observed beneath Ahi Tupua. These observations are consistent with dehydration of the slab and flow of slab‐derived fluids along existing faults into the mantle wedge, that drives flux melting and accounts for the distinctive geochemical signatures and voluminous output of Ahi Tupua calderas. Plain Language Summary: Ahi Tupua is a volcanic region in the North Island of New Zealand that is the most active silicic volcanic system on Earth. It includes the active caldera volcanoes Taupō and Ōkataina. This volcanic region lies above the Hikurangi Subduction Zone, and studies of past eruptions suggest that Ahi Tupua's high rate of activity is driven by fluids released deep in the subduction zone. In this study, we use seismic data from across the entire North Island to investigate earthquakes occurring at depths of 50–300 km within the Hikurangi Subduction Zone. We show that these earthquakes suggest that the subducting oceanic crust is releasing a substantial amount of water into the overlying mantle, causing a large amount of melting and, ultimately, the distinctive volcanism of Ahi Tupua. Key Points: We relocate 397 intermediate‐depth earthquakes beneath Ahi Tupua, central Taupō Volcanic Zone, and compute 47 focal mechanismsMost seismicity occurs within the slab crust and mantle, with subordinate mantle wedge and plate interface faultingHypocenters and focal mechanisms are consistent with slab‐derived fluid fluxing melting of the mantle wedge beneath Ahi Tupua [ABSTRACT FROM AUTHOR]

We report the first catalog of low‐frequency earthquakes in the Hikurangi subduction zone, located beneath the Kaimanawa Range of the North Island at 50 km depth, downdip of regularly recurring (every 4–5 years) deep M7 slow slip events. To systematically detect low‐frequency earthquakes within the regional continuous seismic data, we utilized a matched‐filter approach with template waveforms derived from previous observations of tectonic tremor. We built our catalog of 36 low‐frequency earthquake sources, that produced almost 21,000 events over more than a decade, with two matched‐filter search iterations. In each iteration, the detections were gathered into families and their coherent waveforms processed and stacked to extract high‐quality waveforms, allowing us to pick seismic phase arrivals to locate the low‐frequency earthquakes. We highlight three characteristic features to validate that our detected events are indeed low‐frequency earthquakes: the eponymous deficit of high frequencies in their seismic waveforms, the episodic swarms of activity that define their activity through time, and their location at the plate boundary with a double‐couple source mechanism and geometry consistent with the subduction interface. Considering the observed low‐frequency earthquakes' relationship to neighboring slow slip, we observe the event swarms to occur much more frequently than the M7 slow slip events located just updip. Similar to other deep low‐frequency earthquakes in other subduction zones, we suggest that this characteristic clustering in time is driven by more frequent, smaller slow slip events that are not clearly observable at the surface. Plain Language Summary: Slow slip is episodic fault slip that lasts days, weeks or months, rather than the rapid ruptures of regular earthquakes. Geodetic observations of the surface displacement produced by slow slip suggest that their timing and location influence the seismic cycle of nearby faults and may even trigger large earthquakes. Although slow slip does not produce seismic radiation itself, slow slip is often accompanied by tiny repetitive seismic signals. These tiny seismic events, called low‐frequency earthquakes, can act as a powerful indicator of when and where slow slip is happening. In this study, we develop a new approach to detect low‐frequency earthquakes within continuous seismic waveforms, revealing the first observations of low‐frequency earthquakes in the Hikurangi subduction zone beneath the North Island of New Zealand. Our catalog of low‐frequency earthquakes suggests a complex pattern of slow fault slip at depth, with more frequent activity than geodetic data alone would suggest. The observed low‐frequency earthquake activity in the Hikurangi subduction zone thus represents a unique opportunity to study the slip history at depth beneath the North Island of New Zealand. Key Points: 36 low‐frequency earthquake sources are extracted from continuous waveforms through template matching, deblurring, and unsupervised learningLow‐frequency earthquake sources locate close to the plate boundary with source mechanisms consistent with the subduction interfaceDetected low‐frequency earthquakes are likely triggered by small, frequent, and deep slow slip not geodetically observable at the surface [ABSTRACT FROM AUTHOR]

Seismic source locations are fundamental to many fields of Earth and planetary sciences, such as seismology, volcanology and tectonics. However, seismic source detection and location are challenging when events cluster closely in space and time with signals tangling together at observing stations, such as they often do in major aftershock sequences. Though emerging algorithms and artificial intelligence (AI) models have made processing high volumes of seismic data easier, their performance is still limited, especially for complex aftershock sequences. In this study, we propose a novel approach that utilizes three‐dimensional image segmentation—a computer vision technique—to detect and locate seismic sources, and develop this into a complete workflow, Source Untangler Guided by Artificial intelligence image Recognition (SUGAR). In our synthetic and real data tests, SUGAR can handle complex, energetic earthquake sequences in near real time better than skillful analysts and other AI and non‐AI based algorithms. We apply SUGAR to the 2016 Kaikōura, New Zealand sequence and obtain five times more events than the analyst‐based GeoNet catalog. The improved aftershock distribution illuminates a continuous fault system with extensive fracture zones beneath the segmented, discontinuous surface ruptures. Our method has broader applicability to non‐earthquake sources and other time series image data sets. Plain Language Summary: Detecting and locating earthquakes is fundamental to seismology, volcanology, and tectonics. A number of emerging algorithms, including some based upon artificial intelligence (AI), have made processing large volumes of seismic data much easier. However, their performance is still limited, especially in clustered aftershock sequences whose signals overlap at observing seismographs. We propose a new, AI computer vision‐based approach to this problem, and develop it into a complete earthquake detection and location workflow, named SUGAR. Tests on synthetic and real earthquake data sets show that SUGAR characterizes complex earthquake sequences better than other AI and non‐AI algorithms or professional analysts. We apply SUGAR to the complex aftershock sequence of the 2016 Mw 7.8 Kaikōura, New Zealand earthquake, detecting five times more events than the analyst‐based GeoNet catalog. Whereas surface breaks of the Kaikōura earthquake are highly discontinuous, our improved aftershock distribution supports a continuous fault system surrounded by extensive fracture zones at depth. Our method has broader potential for other types of seismic sources and image series. Key Points: We propose a new seismic source detection and location approach based on the source‐scanning algorithm and 3D image segmentationThis approach outperforms human analysts and popular artificial intelligence (AI) and non‐AI based methods in characterizing intense aftershock sequencesThe resulting catalog of the 2016 Kaikōura earthquake sequence suggests a continuous fault system surrounded by extensive fracturing [ABSTRACT FROM AUTHOR]

The statistical analysis of the impact of the top 50 X-class solar flares (1997–2024) on global seismic activity as well as on the earthquake preparation zones located in the illuminated part of the globe and in an area of 5000 km around the subsolar point was carried out. It is shown by a method of epoch superposition that for all cases, an increase in seismicity is observed, especially in the region around the subsolar point (up to 33%) during the 10 days after the solar flare in comparison with the preceding 10 days. The case study of the aftershock sequence of a strong Mw = 9.1 earthquake (Sumatra–Andaman Islands, 26 December 2004) after the solar flare of X10.16 class (20 January 2005) demonstrated that the number of aftershocks with a magnitude of Mw ≥ 2.5 increases more than 17 times after the solar flare with a delay of 7–8 days. For the case of the Darfield earthquake (Mw = 7.1, 3 September 2010, New Zealand), it was shown that X-class solar flares and M probably triggered two strong aftershocks (Mw = 6.1 and Mw = 5.9) with the same delay of 6 days on the Port Hills fault, which is the most sensitive to external electromagnetic impact from the point of view of the fault electrical conductivity and orientation. Based on the obtained results, the possible application of natural electromagnetic triggering of earthquakes is discussed for the earthquake forecast using confidently recorded strong external electromagnetic triggering impacts on the specific earthquake preparation zones, as well as ionospheric perturbations due to aerosol emission from the earthquake sources recorded by satellites. [ABSTRACT FROM AUTHOR]

We construct a thin‐sheet dynamical model of the New Zealand plate boundary that includes faults. Our model fits fault slip rates, style of distributed deformation, and is constrained by relative plate boundary motion. We assume a pseudo‐plastic rheology and achieve a best fit to slip rate observations with a deviatoric stress magnitude of 20 MPa. Modeled local forces are significant at Puysegur and Hikurangi subduction zones, and smaller forces are related to mantle downwelling beneath South Island and Havre Trough mantle upwelling. Modeled tractions on faults are mostly 5–20 MPa, similar to or slightly smaller than stress magnitudes adjacent to faults. Modeled shear tractions are generally 2–10 MPa, comparable to stress drops during earthquakes. Modeled stress orientations and fault dips suggest that many faults are not optimally oriented for their style of faulting. Notably small traction magnitudes of <5 MPa and shear tractions of <0.5 MPa are modeled for faults in the central North Island Dextral Fault Belt (NIDFB), which we infer to be very poorly oriented. Friction coefficients on faults (ratio of shear stress to effective normal stress) are in the range 0.1–0.3 for major crustal faults such as the Alpine Fault and Marlborough faults, but subduction zones and the NIDFB have values <0.1. We propose that low values of long‐term fault strength, shear stress resolved onto the fault, and overall magnitudes of deviatoric stress in the crust are a consequence of dynamic weakening of faults during fault slip. Plain Language Summary: Earthquakes occur when there is movement along faults. However, the strength of friction resisting movement on faults is debated. We construct a model of major faults through New Zealand that fits observed long‐term fault movement rates. We estimate forces driving movement on faults along with the physical properties of those major faults and of the crust between major faults. We find that many faults are not optimally oriented to move in the direction they are observed to move given the modeled forces acting on them. We estimate low levels of friction on faults, indicating that relatively small forces (averaged over thousands of years) are required to cause movement on faults. Key Points: Crustal deviatoric stress magnitudes are ∼20 MPa and fault tractions are 5–20 MPaShear tractions on faults are 0.5–10 MPa, comparable to earthquake stress dropsFriction coefficients are 0.05–0.3 for most crustal faults and are <0.1 for most subduction‐related faults [ABSTRACT FROM AUTHOR]

Current earthquake forecasting approaches are mainly based on probabilistic assumptions, as earthquakes seem to occur randomly. Such apparent randomness can however be caused by deterministic chaos, rendering deterministic short‐term forecasts possible. Due to the short historical and instrumental record of earthquakes, chaos detection has proven challenging, but more frequently occurring slow slip events (SSE) are promising candidates to probe for determinism. Here, we characterize the SSE signatures obtained from GNSS position time series in the Hikurangi Subduction Zone (New Zealand) to investigate whether the seemingly random SSE occurrence is governed by chaotic determinism. We find evidence for deterministic chaos for stations recording shallow SSEs, suggesting that short‐term deterministic forecasting of SSEs, similar to weather forecasts, might indeed be possible over timescales of a few weeks. We anticipate that our findings could open the door for next‐generation SSE forecasting, adding new tools to existing probabilistic approaches. Plain Language Summary: Since earthquakes appear to occur randomly, the currently available probabilistic predictions are based on past earthquake records. These predictions estimate the likelihood of an earthquake of a given magnitude occurring within a defined time period. In contrast to such probabilistic approaches, deterministic systems are fully predictable, albeit often confined to short time scales due to their potential chaotic behavior. Probing for deterministic predictability in the earthquake cycle is intractable due to the limited historical instrumental record. However, frequently occurring slow slip events ‐ captured by transient GNSS displacements that can last several weeks ‐ provide a unique opportunity to explore deterministic predictability in these types of slow earthquakes. By studying GNSS time series from various stations on New Zealand's North Island, we have discovered evidence suggesting that these irregularly occurring slow slip events might be governed by chaotic determinism. This implies the potential to forecast both timing and magnitude of slow slip events a few weeks in advance using deterministic methods, much like we predict weather patterns. Consequently, our theoretical findings could therefore pave the way for innovative approaches to short‐term slow slip forecasting. Key Points: Nonlinear analysis of GNSS displacement time series unveils evidence for deterministic chaos in slow slip events in New ZealandOur theoretical findings imply that irregularly occurring slow slip events could potentially be forecasted a few weeks in advance [ABSTRACT FROM AUTHOR]

Mt. Ruapehu is an active andesitic stratovolcano, consisting of several peaks with the summit plateau at 2,797 m, making it the tallest active volcano in New Zealand. The extent of the volcano spreads 40 km across with a series of complex faults encompassing almost the entire base of the volcano. A series of earthquakes occurring 20 km west of the summit of Mt. Ruapehu, near the small town of Erua, which preceded the 1995/1996 major volcanic eruption sequence has been proposed as a medium-term precursor for eruptions at Mt. Ruapehu. We use unsupervised machine learning clustering algorithms HDBSCAN and DBSCAN to define anomalous earthquake swarms in the region and determine whether the Erua swarm was unique by identifying key characteristics in space, time and magnitude distribution. HDBSCAN found six spatial cluster zones to the west of Mt. Ruapehu, which have temporal seismic bursts of activity between 1994 and 2023. DBSCAN identified the seismic swarm that preceded the 1995/1996 major eruption, along with one other similar cluster in the same region, which did not coincide with any documented magmatic unrest, suggesting distal seismic swarms at Mt. Ruapehu may not serve as a reliable eruption precursor when observed in isolation. We instead found that earthquake swarms are relatively common at Mt. Ruapehu and the temporal evolution of the earthquake clusters west of Mt. Ruapehu share similar characteristics to seismic swarms identified in other settings related to fluid migration, typical of fault-valve models. [ABSTRACT FROM AUTHOR]

Host‐associated microbial communities are shaped by myriad factors ranging from host conditions, environmental conditions and other microbes. Disentangling the ecological impact of each of these factors can be particularly difficult as many variables are correlated. Here, we leveraged earthquake‐induced changes in host population structure to assess the influence of population crashes on marine microbial ecosystems. A large (7.8 magnitude) earthquake in New Zealand in 2016 led to widespread coastal uplift of up to ~6 m, sufficient to locally extirpate some intertidal southern bull kelp populations. These uplifted populations are slowly recovering, but remain at much lower densities than at nearby, less‐uplifted sites. By comparing the microbial communities of the hosts from disturbed and relatively undisturbed populations using 16S rRNA gene amplicon sequencing, we observed that disturbed host populations supported higher functional, taxonomic and phylogenetic microbial beta diversity than non‐disturbed host populations. Our findings shed light on microbiome ecological assembly processes, particularly highlighting that large‐scale disturbances that affect host populations can dramatically influence microbiome structure. We suggest that disturbance‐induced changes in host density limit the dispersal opportunities of microbes, with host community connectivity declining with the density of host populations. [ABSTRACT FROM AUTHOR]

Tectonic deformation within fault damage zones can influence slope stability and landslide failure mechanisms due to rock mass strength effects and the presence of tectonic structures. Here, we used detailed site investigations to evaluate controls on deformation within the Half Moon Bay landslide complex, located ~1 km from the surface trace of the Hope fault in the South Island of New Zealand. During the 2016 Mw 7.8 Kaikōura earthquake, the slope experienced up to ~13 m of displacement and partially transitioned into a rock avalanche (with a volume of ~350,000 m³). Deep-seated deformation of the entire slope predated the 2016 earthquake. Results of geomorphological analysis, field mapping, geophysical surveys, slope displacement, and a 60-mdeep borehole in the incipient portion of the landslide indicated the presence of a subvertical tectonic fabric and intense fracturing and weathering of the rock mass, which gradually decrease with depth. Based on these results, we established a conceptual model wherein the landslide failure mechanism is a combination of flexural toppling along the subvertical structures coupled with joint-step-path sliding along preexisting, closely spaced discontinuities within the graywacke rock mass. Coseismic slope displacements revealed a large area of incipient failure behind the headscarp of the 2016 rock avalanche, which will likely result in further avalanching at the site. This case study demonstrates that inherited tectonic structures (combined with seismicity and weathering in an oversteepened coastal slope) play an important role in the evolution of hillslopes near active faults. [ABSTRACT FROM AUTHOR]

The evaluation of the b value of the Gutenberg–Richter (GR) law, for a sample composed of n earthquakes, presents a systematic positive bias δ b which is proportional to 1/ n. In this study, we show how to incorporate in δ b the bias introduced by deviations from the GR law. More precisely we show that δ b is proportional to the square of the variability coefficient CV , defined as the ratio between the standard deviation of the magnitude distribution and its mean value. When the magnitude distribution follows the GR law CV = 1 and this allows us to introduce a new graphical procedure, based on the dependence of b on n , which allows us to identify the incompleteness magnitude m c as the threshold magnitude leading to CV = 1. The method is tested on synthetic catalogues and it is applied to estimate m c in Southern California, Japan and New Zealand. [ABSTRACT FROM AUTHOR]

Earthquakes are catastrophic natural disasters, and the built environment requires a quick recovery after such events. Estimating the loss from an earthquake can be complex as unique factors, in addition to conventional repair work, that need to be considered during the postperiod stage. Previous research has been able to identify 11 factors that impact the postearthquake cost estimation for the earthquake damage repair work (CEEDRW) process. Current loss estimation methods such as PACT, SLAT, and SP3 do not incorporate the impact of all these factors. This paper identifies the factors that impact different stages of traditional CEEDRW: precontract estimates, estimates during repair work, and cost calculations after construction. Discussion around methods to adopt these modeling factors into CEEDRW is also presented. A two-stage data collection method was adopted for this paper. Data were collected through semistructured interviews using 19 participants and a questionnaire survey using 92 participants who have experience in the CEEDRW process. The interview data analysis emphasized the usage of 11 factors at the three stages of estimation. Furthermore, survey results identified the most suitable methods of incorporating each factor in CEEDRW. Existing estimation tools used for CEEDRW do not consider a number of factors. This paper suggests the most suitable methods of considering these into an estimation tool that aims to enhance the accuracy and reliability of the CEEDRW process. The methods identified in this paper can be used in developing more reliable future cost estimation models used to determine postearthquake damage repair work. The data were collected from professionals who are experienced in housing repair work in New Zealand. The results vary for other types of geographic regions and construction methods. Currently used postearthquake cost estimation processes for earthquake damage repair work have a lot of drawbacks. To achieve the final aim of developing a standard postearthquake cost estimation model for earthquake damage repair work that is more accurate and faster than current ones, this research achieved one of the objectives of identifying methods that can be used to mitigate problems of the current cost estimation process. The research identifies methods that can be used to include factors that were not fully considered in current postearthquake cost estimation processes. The results of the research will help with increasing the accuracy of the upgraded model. The next step in this process is the develop the upgraded standard postearthquake cost estimation model for earthquake damage repair work. Even with the current findings, cost estimators, builders, and insurance agencies can improve their cost estimation process by including the impact of the factors through the suggested methods. Governments can implement changes to standard construction contracts and policies so that the construction industry can positively manage the cost-varying dynamics of earthquake damage repair work. [ABSTRACT FROM AUTHOR]

This article is concerned with the problem of choosing between competing models for directional data. In particular, we consider the question of whether or not two independent samples of axial data come from the same Bingham distribution. This is not a straightforward question to answer, due to the intractable nature of the parameter-dependent normalizing constant of the Bingham distribution. We propose three different methods to perform this task within a Bayesian framework, and apply the methodology to a real dataset on earthquakes in New Zealand. R code to run our methods is available in online . [ABSTRACT FROM AUTHOR]

Purpose: This paper examines what facilitates the swift reconfiguration of freight movements across transport modes in the wake of a major disaster. Design/methodology/approach: A qualitative research approach focussing on the New Zealand (NZ) domestic freight transport operations in the wake of the 2016 Kaikōura earthquake is used with data collected through 19 interviews with 27 informants. The interviews are thematically analysed by using the framework method. Findings: The paper provides rich and detailed descriptions of the ability of a freight transport system to recover from a disaster through rapid modal shifts. This paper identifies nine factors enabling modular transport operations and highlights the critical role of physical, digital, operational and inter-organisational interconnectivity in the aftermath of a disaster. Originality/value: Although the management of freight disruptions has become a prevalent topic not only in industry and policy-making circles, but also in the academic literature, qualitative research focussing on the ability of commercial freight systems to adapt and recover from a disaster through rapid modal shifts is limited. This qualitative study sheds light on the mechanisms underlying the continuity of freight operations in the wake of a disaster and provides a comprehensive understanding of modular transport operations and the ability of freight systems to keep goods moving. [ABSTRACT FROM AUTHOR]

The impacts of natural disasters on marine mammals are poorly understood and difficult to study, which can hamper management responses following such events.This study provides the first distribution and abundance assessment of New Zealand fur seal (NZFS: Arctocephalus forsteri) colonies around Kaikōura, New Zealand, since a 7.8 magnitude earthquake in November 2016 caused substantial changes to both the local marine and terrestrial environments, and led to the reconstruction of a major highway that runs adjacent to NZFS colonies.Mark–recapture and direct counts in the 2022–2023 breeding season estimated pup production for NZFS breeding colonies along the Kaikōura coast. Using established multipliers, pup estimates were used to provide the first comprehensive population estimate for Kaikōura's NZFS population since the earthquake.Three new colonies and three new subcolonies were assessed and recorded, additional to reassessments of two established colonies. Overall, Kaikōura's NZFS population has grown and spread post‐earthquake, with an upper total population estimate of between 21,560 and 28,327 animals in the 2022–2023 breeding season. Some sites, such as Lynch's Reef, appear to have benefited from earthquake‐induced coastal uplift, with pup production increasing. Contrastingly, the estimated 2,401 (±99) pups produced at Ōhau Point in 2023 is similar to pre‐earthquake estimates. This indicates that the earthquake has disrupted previously documented growth at this site. The distribution of NZFS breeding at Ōhau Point has also changed substantially since the last pre‐earthquake assessment.From these findings, alterations to the Ōhau Point New Zealand Fur Seal Sanctuary and similar protections at other locations on the Kaikōura coast are suggested, as greater numbers of NZFSs are now accessible to human interaction and disturbance. The results demonstrate both how natural disasters and subsequent infrastructure modifications can impact coastal species and how conservation measures may need to be amended accordingly. [ABSTRACT FROM AUTHOR]

'Planning Emergency Levels of Service' (PELOS) are goals for the delivery of infrastructure services following a major hazard event, such as an earthquake or flood. This paper presents an operationalised PELOS framework for the Wellington region based on interviews with emergency and critical infrastructure managers and discusses important changes from the preliminary to the operationalised framework. A shared understanding of these PELOS will help Wellington region infrastructure providers, emergency management professionals and the potentially impacted communities plan for major events. PELOS for the energy, telecommunications, transport, and water sectors have been developed, and high-level interdependencies considered. The PELOS framework can be updated for other regions, by the critical infrastructure entities and emergency managers, using locally relevant hazard scenarios. In turn, this approach can inform the endusers (communities) of the goals of the critical infrastructure providers following a major hazard event. [ABSTRACT FROM AUTHOR]

Tsunamis can have devastating consequences for coastal communities. Yet hazards from future tsunamis are difficult to quantify due to their rarity in the instrumental record. Statistical earthquake catalogs have previously been used to quantify tsunami hazards. For the first time, we use a physics‐based synthetic earthquake catalog to assess probabilistic tsunami hazard in a local region. We analyze a 30,000‐year catalog to capture a wide range of the source complexity evident in tsunamigenic earthquakes. We produce models of land‐surface displacements and subsequent tsunamis from 2,585 earthquakes with magnitude > MW 7.0. Modeled slip of the Hikurangi and Tonga‐Kermadec subduction thrusts generated maximum wave heights at the coast of up to 28 m and these earthquakes pose the greatest tsunami hazard along New Zealand's coastline. The results provide a "proof of concept" for using earthquake simulators for probabilistic tsunami hazard models. They further present a platform upon which next‐generation probabilistic tsunami inundation models may be constructed. Plain Language Summary: Tsunamis with devastating, wide‐reaching consequences are significant hazards to nearly all of the world's coastlines that needs to be analyzed and quantified. Previous tsunami hazard studies have relied on sparse data retrieved from geological and/or probabilistic earthquake models to examine this infrequent but potentially deadly hazard. Consequently, they lack crucial information about the broad range of tsunami hazards resulting from local tsunamis. Our study represents the first time that a physics‐based synthetic earthquake catalog has been used to assess probabilistic tsunami hazard. It overcomes many of the challenges of previous tsunami hazard assessments. We model the tsunamis generated from 2,585 earthquakes which have magnitudes greater than 7.0 from 30,000 years of a synthetic catalog of earthquakes nucleating on both the subduction zones and crustal faults through New Zealand. Tsunami wave heights at the coast of up to 28 m were recorded. Additional analysis indicates that modeled earthquakes on the Hikurangi and Tonga‐Kermadec subduction thrusts pose the greatest hazard along many parts of New Zealand's coastline. Key Points: First use of a physics‐based synthetic earthquake catalog in tsunami hazard assessmentOur assessment demonstrates that near‐field seismic tsunamis can generate maximum wave heights at the coast of up to 28 m around New ZealandOur results provide a pathway toward next‐generation probabilistic tsunami risk modeling [ABSTRACT FROM AUTHOR]

Here we update a catalogue of 2001–2011 New Zealand earthquakes relocated with a 3-D seismic velocity model, which has recent improvements. We use P- and S-wave arrival times from earthquakes during 2001–2011 as these were manually picked with assigned quality. We demonstrate the usefulness of the catalogue by considering results from the southern South Island where GeoNet seismograph spacing is large. Later phase data used automatic picking and processing of arrival times. We relocate the 2019–2020 data from National Geohazards Monitoring Centre (NGMC) and compare seismicity patterns to consider its usefulness. We find that the auto-detected crustal earthquakes are more sparse in most of the southern South Island compared to the earlier analyst-picked data period, including Fiordland, which is one of the most seismically active areas in New Zealand. The auto-detected seismicity pattern is also problematic at greater depth and does not show a seismicity band in the lower crust across Southland evident in 2001–2011 data. The detection capability could be improved with a much denser permanent network. We recommend that the 2001–2011 relocated catalogues be used in studies of tectonics and seismic hazard across the South Island, and in studies that consider New Zealand wide seismicity patterns. [ABSTRACT FROM AUTHOR]

Informed by Māori oral histories that refer to past catastrophic marine inundations, multi-proxy analysis of stratigraphic records from Swamp Bay, Rangitoto ki te Tonga (D'Urville Island) shows evidence of an anomalous deposit extending some 160 m inland. The deposit includes two distinct lithofacies. The lower sand unit is inferred to have been transported from the marine environment, with corresponding increases in the percentages of benthic marine and brackish–marine diatoms, and geochemical properties indicative of sudden changes in environmental conditions. Radiocarbon dating indicates the deposit formation is less than 402 yrs BP, and pollen indicates it is unlikely to be younger than 1870 CE. Core stratigraphy age models and co-seismic chronologies point to the marine unit most likely being emplaced by tsunami transport associated with rupture of the Wairarapa Fault in 1855 CE. The overlying unit of gravel and silt is inferred to be fluvial deposit and slope-wash from the surrounding hills, loosened by ground-shaking following the earthquake. These findings indicate the 1855 CE earthquake may have been more complex than previously thought and, or, available tsunami modelling does not fully capture the local complexities in bathymetry and topography that can cause hazardous and localized tsunami amplification in embayments like Swamp Bay. [ABSTRACT FROM AUTHOR]

Marine radiocarbon (14C) ages are an important geochronology tool for the understanding of past earthquakes and tsunamis that have impacted the coastline of New Zealand. To advance this field of research, we need an improved understanding of the radiocarbon marine reservoir correction for coastal waters of New Zealand. Here we report 170 new ΔR20 (1900–1950) measurements from around New Zealand made on pre-1950 marine shells and mollusks killed by the 1931 Napier earthquake. The influence of feeding method, living depth and environmental preference on ΔR is evaluated and we find no influence from these factors except for samples living at or around the high tide mark on rocky open coastlines, which tend to have anomalously low ΔR values. We examine how ΔR varies spatially around the New Zealand coastline and identify continuous stretches of coastline with statistically similar ΔR values. We recommend subdividing the New Zealand coast into four regions with different marine reservoir corrections: A: south and western South Island, ΔR20 –113 ± 33 yr, B: Cook Strait and western North Island, ΔR20 –171 ± 29 yr, C: northeastern North Island, ΔR20 –143 ± 18 yr, D: eastern North Island and eastern South Island, ΔR20 –70 ± 39 yr. [ABSTRACT FROM AUTHOR]

Characterizing gravelly soil using in situ penetration testing procedures is a significant challenge for geotechnical engineers. The interaction between the penetrometer and large gravel particles can obscure the penetration resistance of the soil matrix, which is the target of the investigation, and lead to significant uncertainty regarding the properties of the soil. Hence, the size of the probe relative to the maximum particle size of the soil matrix is an important factor to consider when performing interpreting and penetration tests. In this respect, the standard penetration test (SPT) and cone penetration test (CPT) can have potential issues in measuring the penetration resistance in certain cases depending on the size and percentage of gravel particles. Recently, the Chinese dynamic cone penetration test (DPT) consisting of a larger-diameter probe with higher hammer energy has been used to develop probabilistic liquefaction triggering curves for gravelly soil. In the present study, an instructive comparison is presented between the performance of the DPT and CPT in evaluating the liquefaction potential of gravelly soils based on in situ testing at the port of Wellington in New Zealand. Gravelly reclamation fill at the port liquefied during the 2016 Mw7.8 Kaikōura earthquake, but only limited parts of the same fill deposits manifested liquefaction during the Mw6.6 Cook Strait and Lake Grassmere earthquakes that occurred in 2013. Triggering analyses have been performed using both DPT- and CPT-based triggering procedures to estimate the potential for liquefaction in these gravelly deposits for these three earthquake events. The CPT-based cyclic resistance ratio (CRR) profiles showed several intermittent spikes with depth due to the interaction of the small-diameter cone with large gravel particles. However, the lower range of values excluding the spikes in the CPT-based CRR profiles primarily governed the liquefaction potential of the reclamation fill, and they are in good agreement with the DPT-based CRR profiles. Both the CPT and DPT-based triggering analyses successfully estimated liquefaction manifestation during the Kaikōura event, some liquefaction manifestation during the Cook Strait event and very limited manifestation during the Lake Grassmere event, which is largely consistent with observations. This case history clearly shows that sandy gravel can liquefy. In this case, the sand content was high enough (>30%) to fill the pore space and reduce the permeability so that it could liquefy. For sandy gravel at Centerport, New Zealand, with D50 (50% finer particle size) between 3 and 10 mm, the ratio of D50 to penetrometer diameter (Dp) would occasionally exceed 33% to 50% for the CPT, and some artificial increase in penetration resistance would be expected. In contrast, the D50 to Dp ratio for the DPT would not exceed 15%, and gravel particles would not affect the DPT blow count. This assessment is borne out in the comparison between the CRR from the CPT and DPT. For example, the CRRs from the DPT were relatively constant in the sandy gravel, whereas the CRRs from the CPT showed several spikes with depth, but were otherwise consistent with those from the DPT. In some cases, the CPT cannot penetrate layers with larger or denser gravel particles. The DPT cannot identify nonliquefiable cohesive layers; therefore, samples from a companion borehole are needed to identify them. The good agreement between the CRRs from the CPT and DPT for three earthquakes confirmed the reliability of these two independently developed methods. [ABSTRACT FROM AUTHOR]

With critical lessons drawn from past major earthquakes, the engineering community is appealing for a fundamental shift in the existing design philosophy for structures in seismic zones. One strategy is to endow structures with self-centering (SC) capability. While the concept of SC structures is not new, many novel technologies have been recently emerging that are more efficient, compact, and cost-effective; on the other hand, growing controversy and dispute have also been appearing with deepening investigations. This paper presents a critical review of the evolution of SC technologies and systems for both researchers and practitioners, with an emphasis on post-tension (PT), high-performance spring, and shape memory alloy (SMA) strategies. These SC technologies, together with various energy dissipation options, form the basis of a large part of the newly proposed SC philosophies. This review also includes typical SC structural members such as beam-to-column connections, braces, dampers, shear walls, bridge piers, and isolation bearings, followed by a discussion on the dynamic behavior from a system-level point of view. Available design approaches for SC structures are also touched upon, and practical applications that have emerged over the past decades in several countries including Canada, China, New Zealand, and the US are presented. This paper concludes with an executive summary that covers technological advances, knowledge gaps, and future research directions. [ABSTRACT FROM AUTHOR]

Artefacts in museums, galleries, and private collections have great cultural value. In regions with high seismicity, earthquake shaking can pose significant risk of irreversible damage to such pieces. Various seismic protection methods have been proposed in the past for different types of artefacts. This study investigates one of the commonly used methods in New Zealand which consists in applying adhesives to anchor relatively small artefacts. Guidance is provided to determine the size and number of adhesives required for an artefact to survive design-level earthquake shaking. In addition, for large objects where adhesives alone are insufficient, a simple cost-effective base-isolation platform is proposed to reduce the seismic vulnerability of the artefacts. This platform is designed such that it can be assembled and positioned by museum conservators or private collectors. The adhesive material properties are determined through direct tension and shear experimental tests. The friction properties of the base-isolated substrate are determined through unidirectional quasi-static and cyclic load tests. Performance of the proposed methodology is gauged by subjecting the artefacts to shake table testing using a recorded earthquake motion. Results suggest that the recommended seismic protection solution performs as expected. [ABSTRACT FROM AUTHOR]

Landslide deposits preserved in the geological record afford opportunities to better inform hillslope and seismic hazard and risk models, particularly in regions where observational records are short. In the Southern Alps of New Zealand, small coseismic landslides are frequent, but the geological record preserves several instances of more substantial (> 1 km3) but infrequent mass failures. With an estimated volume of 27 km3, the giant Green Lake Landslide represents one of the largest subaerial landslides on Earth. Previous work has suggested this deep-seated mass movement was most likely triggered by high-intensity seismic shaking, but that local structural weakness and/or glacial debuttressing may help to explain the anomalously large failure volume. Resolving the potential contribution of the latter is important given predictions concerning alpine deglaciation in the coming decades to centuries. Key to resolution are secure chronologies of landslide emplacement and past glacier change. Here we present in situ cosmogenic 10Be exposure ages from the Green Lake Landslide that suggest an emplacement age of 15.5 ± 0.7 ka. Recent work shows that glacial retreat in the region was underway by 19 ka, indicating that the Green Lake Landslide was emplaced 3–4 kyr after the onset of glacier retreat. Given the geometry of the former confining valley glacier, we expect that the deglaciation-landslide age gap is closer to the upper end of this estimate. If correct, this conclusion places greater weight on the roles of local geological structure and/or a great earthquake as factors contributing to the exceptionally large volume of this event. [ABSTRACT FROM AUTHOR]

Aim: Both macroecology and disturbance ecology have long been used to characterize population‐ and community‐level patterns across scales, but the integration of both approaches in characterizing disturbed ecosystems is rare. Here, we use the maximum entropy theory of ecology (METE) to model the individual size distribution (ISD) of trees in pre‐ and post‐disturbance tree populations and estimate the corresponding metabolic scaling exponents. Location: New Zealand. Time Period: 1987–1999. Major Taxa Studied: Mountain beech (Fuscospora cliffortioides Nothofagaceae). Methods: METE uses information entropy and empirical macro‐state variables to constrain predictions of ecological distributions related to biodiversity. METE has successfully predicted a range of biodiversity metrics in static or relatively undisturbed conditions. However, METE can fail to accurately model ecological patterns in disturbed ecosystems. We extend existing theoretical predictions to a highly disturbed ecosystem by treating the metabolic scaling exponent and Lagrange multipliers as free parameters in METE. Results: We showed that the fully parameterized METE (FP‐METE) model reasonably predicted the ISD of mountain beech populations in a monodominant forest after a strong earthquake, which restructured the forest. Furthermore, the FP‐METE model revealed that decreasing metabolic scaling exponent drove the substantial decline of total metabolic rate energy and the redistribution of energy towards smaller trees after the earthquake. Increased number of small trees was not sufficient to capture the full impact of disturbance on forest energy use. Main Conclusions: Our FP‐METE model applies an informatics approach to estimate the metabolic scaling relationship. We find that instead of maintaining a fixed value, the metabolic scaling exponent is variable among populations, and declines significantly after an earthquake disturbance. This leads to major shifts in the total population metabolic energy and energy distribution. With this approach, we now have the opportunity to advance beyond categorizing forms of mathematical distributions that describe biodiversity patterns and move into a predictive framework where the true constraints on ecosystems and their dynamics emerge. [ABSTRACT FROM AUTHOR]

This paper investigates the impact of an earthquake on households' perception of the seismic risks associated with residential locations—and, consequently, the impact of this change in perceptions on real estate prices—by performing revealed preference analysis on a unique data set of house prices and damage claims after the 2010/2011 Canterbury earthquake in New Zealand. We show that both informational and heuristic obstacles could have caused households to underestimate location earthquake risk before the quake and overreact to it after the quake. Our findings highlight the importance of quake-related information for seismic risk management and are robust to households' risk preferences in neighborhood propensity score matching. [ABSTRACT FROM AUTHOR]

Coastal hillslopes often host higher concentrations of earthquake-induced landslides than those further inland, but few studies have investigated the reasons for this occurrence. As a result, it is unclear if regional earthquake-induced landslide susceptibility models trained primarily on inland hillslopes are effective predictors of coastal susceptibility. The 2016 Mw 7.8 Kaikōura earthquake on the northeastern South Island of New Zealand resulted in ca. 1600 landslides > 50 m 2 on slopes > 15 ∘ within 1 km of the coast, contributing to an order of magnitude greater landslide source area density than inland hillslopes within 1 to 3 km of the coast. In this study, logistic regression modelling is used to investigate how landslide susceptibility differs between coastal and inland hillslopes and to determine the factors that drive the distribution of coastal landslides initiated by the 2016 Kaikōura earthquake. Strong model performance (area under the receiver operator characteristic curve or AUC of ca. 0.80 to 0.92) was observed across eight models, which adopt four simplified geology types. The same landslide susceptibility factors, primarily geology, steep slopes, and ground motion, are strong model predictors for both inland and coastal landslide susceptibility in the Kaikōura region. In three geology types (which account for more than 90 % of landslide source areas), a 0.03 or less drop in model AUC is observed when predicting coastal landslides using inland-trained models. This suggests little difference between the features driving inland and coastal landslide susceptibility in the Kaikōura region. Geology is similarly distributed between inland and coastal hillslopes, and peak ground acceleration (PGA) is generally lower in coastal hillslopes. Slope angle, however, is significantly higher in coastal hillslopes and provides the best explanation for the high density of coastal landslides during the 2016 Kaikōura earthquake. Existing regional earthquake-induced landslide susceptibility models trained on inland hillslopes using common predictive features are likely to capture this signal without additional predictive variables. Interestingly, in the Kaikōura region, most coastal hillslopes are isolated from the ocean by uplifted shore platforms. Enhanced coastal landslide susceptibility from this event appears to be a legacy effect of past erosion from wave action, which preferentially steepened these coastal hillslopes. [ABSTRACT FROM AUTHOR]

The 2016 Kaikoura earthquake, New Zealand, ruptured more than a dozen faults, making it difficult to prescribe a model fault for analyzing the event by inversion. To model this earthquake from teleseismic records, we used a potency density tensor inversion, which projects multiple fault slips onto a single model fault plane, reducing the non-uniqueness due to the uncertainty in selecting the faults' orientations. The resulting distribution of potency-rate density tensors is consistent with observed surface ruptures. In its initial stage, the rupture propagated northeastward primarily at shallow depths. Later, the rupture propagated northeastward at greater depths beneath a gap in reported surface ruptures. The main rupture phase started in the northeastern part of the Kekerengu fault after 50 s and propagated bilaterally to the northeast and southwest. The non-double-couple component grew to a large fraction of the source elements as the rupture went through the junction of the Jordan Thrust and the Papatea fault, which suggests that the rupture branched into both faults as it back-propagated toward the southwest. The potency density tensor inversion sheds new light on the irregular evolution of this earthquake, which produced a fault rupture pattern of unprecedented complexity. Our source model of the 2016 Kaikoura earthquake (e.g., back-rupture propagation) could prompt research to determine a more realistic model with segmented faults using near-field data. [ABSTRACT FROM AUTHOR]

Objective: To report on post-traumatic growth and post-traumatic stress following the Canterbury earthquakes and to quantify the relationships between exposure to the earthquakes, post-traumatic growth and post-traumatic stress. Method: The Christchurch Health and Development Study is a longitudinal birth cohort study of New Zealanders aged 40 years at the time of latest assessment in 2017. A total of 455 participants were exposed to the Canterbury earthquakes and assessed in 2012 and 2017. Post-traumatic growth was measured in 2017 using the Post-traumatic Growth Inventory. Earthquake-related post-traumatic stress was measured in 2012 using post-traumatic stress disorder items from the Diagnostic Interview Schedule. Post-traumatic growth and post-traumatic stress were modelled using measures of earthquake impact and subjective measures of earthquake consequences (peri-traumatic stress and disruption distress). Results: There was an indirect relationship between earthquake impact and post-traumatic growth. This was mediated via disruption distress. There was also an indirect relationship between earthquake impact and post-traumatic stress. This was mediated via peri-traumatic stress and disruption distress. Post-traumatic growth and post-traumatic stress were not significantly related. Conclusions: Measurement of post-traumatic growth and post-traumatic stress is required for a holistic understanding of disaster consequences. Subjective assessment of distress following disasters is required to predict their psychological effects. [ABSTRACT FROM AUTHOR]

Objective: Long-term studies following disasters are rare. It is important to quantify long-term effects of disasters to determine impacts on populations over time. We therefore aim to report the long-term associations between exposure to the Canterbury earthquakes and common mental disorders, taking into account potential confounding factors. Methods: The Christchurch Health and Development Study is a 40-year longitudinal study of a birth cohort of New Zealand children (635 males and 630 females). The Christchurch Health and Development Study includes 884 participants with data on earthquake exposure and mental health outcomes at ages 34 and 40 years. Rates of Diagnostic and Statistical Manual of Mental Disorders (4th ed.) disorders were measured categorically and using an expanded definition that included sub-syndromal symptoms. The current impact of the earthquakes is reported using 12-month prevalence data 7 years after the earthquakes. The cumulative impact of the earthquakes over the 7 years since onset is also reported. Results: There was a linear trend towards increasing rates of disorder with increasing exposure to the earthquakes. After adjusting for covariates, the 12-month prevalence of anxiety disorder symptoms was significantly increased (p = 0.003). The earthquakes were also associated with cumulative increases in symptoms of post-traumatic stress disorder (p < 0.001), anxiety disorder (p = 0.016), nicotine dependence (p = 0.012), and the total number of disorders (p = 0.039). Conclusion: The Canterbury earthquakes were associated with persistent increases in Anxiety Disorder symptoms 7 years after their onset. The earthquakes were also associated with cumulative increases in symptoms of common psychiatric disorders. The magnitude of these effects is small, may no longer be clinically significant and has decreased over time. [ABSTRACT FROM AUTHOR]

In mountainous areas, landslides induced by destructive earthquakes are one of the main causes of human casualties, which is an important link in the chain of earthquake hazards. Earthquake-triggered landslides are mainly controlled by three factors, namely seismic property, topography, and geology. Many studies have been conducted on these controlling factors of earthquake-triggered landslides. However, little is known about the effect of coseismic displacement on the distribution of landslides under different slope aspects and slope angles, hindering our understanding of the mechanism of inducing landslides by the combination of surface displacement and slope geometry at the local scale and leading to controversial opinions about the abnormal number of earthquake-triggered landslides in several cases. Here, we took the 2008 Wenchuan Mw7.9 earthquake in China, the 2015 Gorkha Mw7.8 earthquake in Nepal, and the 2016 Kaikōura Mw7.8 earthquake in New Zealand as examples to investigate the relationship between the distribution of large earthquake-triggered landslides and the three-dimensional (3D) coseismic displacement field. We divided the landslide-prone area around the epicenter into regular grids and calculated the 3D coseismic displacement in each grid according to the radar satellite images and slip distribution model. Then, the 3D coseismic displacement was projected to two coordinate systems related to the slope where the landslides were located for statistical analysis. We determined that the surface uplift perpendicular to the slope is more likely to induce landslides, particularly when combined with large slope angles. Meanwhile, the number of landslides will be significantly reduced where the subsidence occurs. Regardless of uplift or subsidence, landslides are more likely to occur when the direction of coseismic horizontal displacement is far from the slope. The larger the slope angles are, the greater the effects of horizontal displacement and slope aspect. A dominant slope aspect also exists for earthquake-triggered landslides, which is different from the mean slope aspect calculated from the background topography. This dominant aspect angle is related to the focal mechanism and striking angle of surface rupture. These results indicate that we can simulate the 3D coseismic displacement field from known fault location and earthquake mechanism and combine the topographic data for landslide risk assessment in earthquake-prone mountainous areas to minimize the damage caused by possible earthquake-triggered landslides. [ABSTRACT FROM AUTHOR]

We examined the stratigraphy of alluvial fans formed at the steep range front of the Southern Alps at Te Taho, on the north bank of the Whataroa River in central West Coast, South Island, New Zealand. The range front coincides with the Alpine Fault, an Australian‐Pacific plate boundary fault, which produces regular earthquakes. Our study of range front fans revealed aggradation at 100‐ to 300‐year intervals. Radiocarbon ages and soil residence times (SRTs) estimated by a quantitative profile development index allowed us to elucidate the characteristics of four episodes of aggradation since 1000 CE. We postulate a repeating mode of fan behaviour (fan response cycle [FRC]) linked to earthquake cycles via earthquake‐triggered landslides. FRCs are characterised by short response time (aggradation followed by incision) and a long phase when channels are entrenched and fan surfaces are stable (persistence time). Currently, the Te Taho and Whataroa River fans are in the latter phase. The four episodes of fan building we determined from an OxCal sequence model correlate to Alpine Fault earthquakes (or other subsidiary events) and support prior landscape evolution studies indicating ≥M7.5 earthquakes as the main driver of episodic sedimentation. Our findings are consistent with other historic non‐earthquake events on the West Coast but indicate faster responses than other earthquake sites in New Zealand and elsewhere where rainfall and stream gradients (the basis for stream power) are lower. Judging from the thickness of fan deposits and the short response times, we conclude that pastoral farming (current land‐use) on the fans and probably across much of the Whataroa River fan would be impossible for several decades after a major earthquake. The sustainability of regional tourism and agriculture is at risk, more so because of the vulnerability of the single through road in the region (State Highway 6). [ABSTRACT FROM AUTHOR]

The 14 November 2016, Mw 7.8 Kaikoura, New Zealand earthquake offers an unprecedented opportunity to observe the heterogeneity in stress field over a very complex fault system where the subduction zone converges with the strike-slip faults system. Here, we report the pre- and post-seismic stress field asperity for the first time in terms of the b value variations associated to the Kaikoura earthquake. Pre-seismic disparity of b values indicates the existence of two prominent low b value clusters, one in the neighborhood of the epicenter and the other just to the northeast of the earthquake rupture zone. Owing to the co-seismic stress release near the epicentral area, the pattern of low b value has become negligible in the post-seismic period. However, the pattern of low b value in the northeast of the rupture zone remains unchanged in the post-seismic period and indicates the unreleased strain energy in the province. The stress fields inferred from the inversion of the focal mechanism during pre- and post-seismic periods of the event suggest a strike-slip mechanism with a horizontal maximum stress axis (σ1) in the WNW-ESE direction. Nevertheless, before and after the earthquake, the stress field direction did not change significantly, indicating that the energy released during the Kaikoura event was insufficient to alter the stress orientations in the complex fault system. [ABSTRACT FROM AUTHOR]

The magnitude 7.8 earthquake that struck North Canterbury, on the east coast of New Zealand's South Island on 14 November 2016 had significant impacts and implications for the community of Kaikōura and surrounding settlements. The magnitude and scope of this event has resulted in extensive and ongoing geological and geophysical research into the event. The current paper complements this research by providing a review of existing social science research and offering new analysis of the impact of the earthquake and its aftermath on community resilience in Kaikōura over the past five years. Results demonstrate the significant economic implications for tourism, and primary industries. Recovery has been slow, and largely dependent on restoring transportation networks, which helped catalyse cooperation among local hospitality providers. Challenges remain, however, and not all sectors or households have benefited equally from post-quake opportunities, and long-term recovery trajectories continue to be hampered by COVID-19 pandemic. The multiple ongoing and future stressors faced by Kaikōura require integrated and equitable approaches in order to build capability and capacity for locally based development pathways to ensure long-term community resilience. [ABSTRACT FROM AUTHOR]