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With the advancement of digital technology, the collection of pavement performance data has become commonplace. The improvement of tools to extract useful information from pavement databases has become a priority to justify expenditures. This paper presents a case study of PaveMD, a tool that integrates multi-dimensional data structures with a data-driven fuzzy approach to identify good performing pavement sections. Combining this tool with an innovative paradigm where the focus is on repeating success can bring additional value to existing pavement databases. The case study shows that PaveMD can identify pavement sections that are performing well by comparing performance measures for the New Zealand context. In this paper, PaveMD's development is described, and its implementation is showcased using data from the New Zealand Long-Term Pavement Performance (LTPP) database. It is recommended that this approach be further developed and extended to other infrastructure databases internationally. [ABSTRACT FROM AUTHOR]

The near‐surface electrical properties of faults can change with seasonal climate, depending on the nature of the materials filling the faults, e.g. fault gouge vs fractured rock, and be subject to seasonal weather changes. A period of dry weather, especially in a hot climate, can dry out the near‐surface sections of faults that are filled with porous materials, thus increasing the electrical resistivity, yet may not affect a fault that is filled with fine‐grained material that retains moisture well. Conversely, a sustained period of wet weather can fill porous faults with water, thus decreasing the resistivity. To illustrate the impact of seasonal weather changes on the near‐surface properties of faults, we conducted electrical imaging and ground‐penetrating radar surveys during the late spring, summer, and early autumn on the Glen Lyon and Benmore segments of the Ostler Fault, respectively, in the South Canterbury and Central Otago provinces of the South Island of New Zealand. The changes in the response are clear: seasonal weather changes can affect the near‐surface properties of faults, and the geophysical responses from the near‐surface faults can vary depending on the nature of the material filling the fault. [ABSTRACT FROM AUTHOR]

Ambiguous landscape histories can arise from equivocal or incomplete geomorphological, sedimentological or geochronological evidence. In this study, we apply quantitative analyses to robustly assess the origin and age of a field of rounded mounds, known as 'The Hillocks'. Using clast analysis, the sediment is shown to be consistent with a landslide origin but inconsistent with other glacial sediments in the region. Cosmogenic 10Be exposure age dating suggests The Hillocks formed ~8 ka. Ground‐penetrating radar reveals that the deposit rests upon deltaic foreset beds; combined with topographical data, we calculate a deposit volume of ~15–27 M m3, consistent with the estimated volume of the proposed source area. Overall, our data support a rock avalanche origin, indicating that by 8 ka the valley was ice‐free at The Hillocks' location, and the level of Lake Wakatipu was lower than 340 m asl by this time. The Dart River delta shoreline was situated somewhere between The Hillocks and the present day shoreline at that time, and has prograded at a maximum average rate of 1 m a−1 since ~8 ka. These findings are significant given the lack of landforms by which to constrain glacial or post‐glacial landscape histories in this region of New Zealand. Copyright © 2019 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Beach ridge stratigraphy can provide an important record of both sustained coastal progradation and responses to events such as extreme storms, as well as evidence of earthquake induced sediment pulses. This study is a stratigraphic investigation of the late Holocene mixed sand gravel (MSG) beach ridge plain on the Canterbury coast, New Zealand. The subsurface was imaged along a 370 m shore‐normal transect using 100 and 200 MHz ground penetrating radar (GPR) antennae, and cored to sample sediment textures. Results show that, seaward of a back‐barrier lagoon, the Pegasus Bay beach ridge plain prograded almost uniformly, under conditions of relatively stable sea level. Nearshore sediment supply appears to have created a sustained sediment surplus, perhaps as a result of post‐seismic sediment pulses, resulting in a flat, morphologically featureless beach ridge plain. Evidence of a high magnitude storm provides an exception, with an estimated event return period in excess of 100 years. Evidence from the GPR sequence combined with modern process observations from MSG beaches indicates that a palaeo‐storm initially created a washover fan into the back‐barrier lagoon, with a large amount of sediment simultaneously moved off the beach face into the nearshore. This erosion event resulted in a topographic depression still evident today. In the subsequent recovery period, sediment was reworked by swash onto the beach as a sequence of berm deposit laminations, creating an elevated beach ridge that also has a modern‐day topographic signature. As sediment supply returned to normal, and under conditions of falling sea level, a beach ridge progradation sequence accumulated seaward of the storm feature out to the modern‐day beach as a large flat, uniform progradation plain. This study highlights the importance of extreme storm events and earthquake pulses on MSG coastlines in triggering high volume beach ridge formation during the subsequent recovery period. © 2019 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Icy debris fans have recently been described as fan shaped depositional landforms associated with (or formed during) deglaciation, however, the subsurface characteristics remain essentially undocumented. We used ground penetrating radar (GPR) to non-invasively investigate the subsurface characteristics of icy debris fans (IDFs) at McCarthy Glacier, Alaska, USA and at La Perouse Glacier, South Island of New Zealand. IDFs are largely unexplored paraglacial landforms in deglaciating alpine regions at the mouths of bedrock catchments between valley glaciers and icecaps. IDFs receive deposits of mainly ice and minor lithic material through different mass-flow processes, chiefly ice avalanche and to a lesser extent debris flow, slushflow, and rockfall. We report here on the GPR signal velocity observed from 15 different wide-angle reflection/refraction (WARR) soundings on the IDFs and on the McCarthy Glacier; the effect of GPR antenna orientation relative to subsurface reflections; the effect of spreading direction of the WARR soundings relative to topographic contour; observed differences between transverse electric (TE) and transverse magnetic (TM) antenna polarization; and a GPR profile extending from the McCarthy Glacier onto an IDF. Evaluation of the WARR soundings indicates that the IDF deposits have a GPR signal velocity that is similar to the underlying glacier, and that the antenna polarization and orientation did not prevent identification of GPR reflections. The GPR profile on the McCarthy Glacier indicates that the shallowest material is layered, decreases in thickness down fan, and has evidence of brittle failure planes (crevasses). The GPR profile and WARR soundings collected in 2013 indicate that the thickness of the McCarthy Glacier is 82 m in the approximate middle of the cirque and that the IDF deposits transition with depth into flowing glacial ice. [ABSTRACT FROM AUTHOR]

Geophysical imaging of coastal dune stratigraphy near Haast, South Westland, provides insight into coseismic dune modification on a seismically active coastline. Complementary ground-penetrating radar and electrical imaging responses reveal low-angle features that apparently truncate and offset dune bedding. Complex attribute analysis of the GPR profiles is consistent with truncated bedding. One feature is near-coastal and separates post-seismic dunes that have been attributed to the 1717 Alpine Fault and 1826 Fiordland earthquakes. Another is inland, coincident with an incised stream channel. Superficially, the truncations might be interpreted as erosional features caused by large storms; however, the truncating features penetrate and appear to disrupt the wave base. We therefore suggest the near-coastal truncation is either a translational feature, such as a slide, or more likely an erosional record of a tsunami generated by the 1826 Fiordland earthquake. The inland feature records a previous event, the cause of which needs further investigation. [ABSTRACT FROM PUBLISHER]

The Manawahe Fault is located at the boundary between the tectonic Whakatane and the magmatic Okataina segments of the Taupō Rift. We investigate prehistoric ground surface fault ruptures and their timing in association with volcanic eruptions of the Okataina Volcanic Centre (OVC), using geomorphic fault mapping, paleoseismic trenching, ground penetrating radar and shallow drillcores. Paleoseismic trench data across the major strand shows that the Manawahe Fault ruptured at least seven times in the last c. 9.5 cal. ka (with a possible rupture 8 just prior to c. 9.5 cal. ka). At least four of these surface fault ruptures occurred during, or immediately prior to, volcanic eruptions. These eruptions, named Whakatane (c. 5.5 cal. ka – 1 fault rupture), Mamaku c.8 cal. ka −1 fault rupture), and the Rotoma (c. 9.5 cal. ka - 2-3 fault ruptures), were all sourced from the nearby Haroharo Volcanic Complex nested within the OVC, one of the two currently active volcanic lineaments within the OVC. Ground penetrating radar and drillcore data show that the Manawahe Fault has a slip rate of c. 3 mm/yr and that it only formed recently (< 26.5 ka ago), much more recently than the last caldera forming eruption, the c. 61 ka Rotoiti eruption. Fault rupture recurrence is 1580–2000 years. We discuss possible modes of ruptures of the Manawahe Fault in association with modes of volcanic unrest and magmatic processes; whether these prehistoric ruptures were seismogenic or not, and what the implications are for volcanic and seismic hazard. • Paleoseismic studies identify large prehistoric fault ruptures occur with volcanic eruptions. • Stress triggering between faults and volcanos is the most likely mode of interaction. • Fault slip rate in volcanic environments vary with evolution of nearby magmatic systems. • Large earthquakes triggered by volcanic eruptions need more consideration in seismic hazard. • Large earthquakes on nearby faults are underappreciated in volcanic hazard assessment. [ABSTRACT FROM AUTHOR]

Ground penetrating radar (GPR) is a new technique in field sciences and is now commonly applied to studies of coastal dunes and beaches. The technique has yet to be applied on hard rocky coasts, and its ability to discern subsurface stratigraphy has great potential for investigating landform evolution on tectonically active shorelines where erosional surfaces are often buried by sediments derived from marine and nonmarine sources. In this study, we test the resolution of a 100- and 250-MHz GPR system on a series of Holocene uplifted shore platforms and gravel beaches in Wellington, New Zealand. The sediment thickness at the sites investigated ranged from a thin veneer to many meters and is composed of a mix of sand and gravel-sized material. It was found that the 100-MHz antenna did not have the resolution of the 250-MHz antenna and could not distinguish the buried platform surface. Using the 250-MHz antenna, bedding features within the unconsolidated sediment and the bedrock-sediment interface could be discerned. The high relief of the bedrock (meter scale), which outcropped on the surface, and the presence of buried boulders caused significant interference to the radar profiles through the creation of multiple and hyperbolic reflections. Despite these reflections, the GPR was able to quantify the morphology of the buried shore platform, thus indicating the utility of this technique for rocky coast research. [ABSTRACT FROM AUTHOR]

Previous research on debris-flow deposit structure typically reports little to no visually discernible stratigraphy. The preliminary findings presented here provide evidence for more complex internal deposit architecture with inverse grading and subunits thought to reflect individual flow surges. Ground-penetrating radar surveys, geospatial data and field observations are used to describe 10 subunits traceable over the 14 lateral radargrams imaging the lower 38 m of the deposit. Additional subunits are depicted further upslope in a longitudinal transect. As well as demonstrating the need for continued investigation of deposit architecture using non-traditional techniques, these results may help improve future interpretations of post-event deposits. [ABSTRACT FROM AUTHOR]

Abstract: Prior to the recent highly damaging M 7.1 earthquake near the city of Christchurch on the South Island of New Zealand, we recorded coincident high-resolution seismic and ground-penetrating radar (GPR) data across parts of the northwest Canterbury Plains. The seismic reflection images reveal a vast network of interconnected faults and folds below a seemingly undisturbed flat surface. To complement the seismic images, which only provide limited information on the very shallow subsurface (i.e., <20m), we have now processed and analysed the GPR data. The migrated GPR images are dominated by complex reflection patterns characteristic of glaciofluvial sediments. Such sediments eroded from the Southern Alps are observed at the surface throughout our study site. Although it is difficult to distinguish between complexities associated with complicated sedimentation processes and disruptions and offsets of GPR reflections associated with recent movements on faults and folds, we identify a number of regions where the GPR data are consistent with tectonic deformation of Holocene sediments. Two of these regions straddle an interpolated connection between active faults mapped at the surface. In a third region, the development of river terraces imaged in the GPR data may have been affected by slip on newly discovered underlying faults. The most significant near-surface deformation, which is apparent on a coincident seismic reflection image, P-wave tomogram and GPR image, is observed on the flank of a major anticline that appears to have been thrust close to the surface along a reverse fault. Some of the faults and folds resolved in our seismic and GPR data may have been reactivated during the recent period of intense seismicity. [Copyright &y& Elsevier]

SUMMARY In places where sedimentation and erosion compete at fast rates, part of the record of past earthquakes on faults may be buried, hence hidden, in the first few metres below the surface. We developed a novel form of palaeoseismology, of geophysical type, based on the use of a dense pseudo-3-D Ground Penetrating Radar (GPR) survey to investigate such possible buried earthquake traces, on a long, fast-slipping strike-slip fault (Hope fault, New Zealand), at a site (Terako) where marked alluvial conditions prevail. We first used LiDAR data to analyse the ground surface morphology of the 2 km2 site at the greatest resolution. Nineteen morphological markers were observed, mainly alluvial terrace risers and small stream channels that are all dextrally offset by the fault by amounts ranging between 3 and 200 m. The measurements document about 10 past earthquake slip events with a mean coseismic slip of 3.3 ± 1 m, with the most recent earthquake event having a slip of 3 ± 0.5 m. We then investigated a detailed area of the site (400 × 600 m2) with pseudo-3-D GPR. We measured 56, ≈ 400 m long, 5-10 m spaced GPR profiles (250 MHz), parallel to the fault and evenly distributed on either side. The analysis revealed the existence of a palaeosurface buried at about 3 m depth, corresponding to the top of alluvial terraces of different ages. That buried surface is incised by a dense network of stream channels that are all dextrally offset by the fault. We measured 48 lateral offsets in the buried channel network, more than twice than at the surface. These offsets range between 6 and 108 m, as observed at the surface, yet provide a more continuous record of the fault slip. The similarity of the successive slip increments suggests a slip per event averaging 4.4 ± 1 m, fairly similar to that estimated from surface data. From the total 'surface and buried' 67 offset collection, we infer that a minimum of 30 large earthquakes have broken the Hope fault at the Terako site in the last about 6-7 kyr, with an average coseismic slip of 3.2 ± 1 m, a minimum average recurrence time of about 200 yr, and a magnitude of at least Mw 7.0-7.4. Our study therefore confirms that part of the record of past earthquakes may indeed reside in the first few metres below the surface, where it may be explored with geophysical, GPR-based palaeoseismology. Developing such a new palaeoseismological tool should provide rich information that may complement surface observations and help to document the past earthquakes on faults. [ABSTRACT FROM AUTHOR]

Abstract: Where they are preserved, landforms that have been truncated and offset by past fault movements provide potentially valuable quantitative data that can be used to estimate slip rates. At such locations, it is important to investigate the fault zone in sufficient detail to understand how displacements are accommodated on individual fault strands. At a site along a northern section of the Alpine fault zone on the South Island of New Zealand, surface mapping of a series of faulted river terraces and channels has revealed a complicated and poorly understood paleoearthquake history. We have acquired high-resolution 2- and 3-D ground-penetrating radar (GPR) data over a large area (~500×500m) of the terraces to map along-strike changes in shallow (<20m) fault zone morphology. By identifying distinct reflection patterns within the topographically migrated 3-D GPR volumes and extrapolating them to the longer and more widely spaced GPR profiles, we determined the subsurface extent of two main structural/depositional facies that were juxtaposed by three left-stepping en-echelon fault strands. Two regions of warped strata are interpreted to result from transpressive folding between the overlapping strands, where displacement is transferred from one fault to the next. We suggest that diffuse deformation between the overlapping fault tips results in anomalously low estimates for horizontal and vertical fault displacements of some geomorphic features. [Copyright &y& Elsevier]

Because surface processes can frequently remove, mask or suppress the surface expression of faults, geophysical imaging is needed to provide information on the geometric expression of the fault in the subsurface, including dips, the presence or absence of splays and folds and the nature of the material in the fault plane. Subsurface data become especially important where a step-over occurs, however the mechanism of the step-over is not clear. The Ostler Fault is a major thrust fault in the Mackenzie Basin of the South Island of New Zealand. The geometry of the fault changes along its length, with a number of growing anticlines and step-overs forming the Ostler Fault Zone (OFZ). One of these anticlines occurs along the Benmore segment of the OFZ. A three-dimensional (3-D) ground penetrating radar (GPR) survey was carried out to supplement detailed surface topographic mapping and help characterize the nature of the OFZ at Benmore. To cover the 1 km length of the step-over, the 3-D survey was done with a coarse yet regular 50 m line spacing. The individual fault splays were continuous and could be traced from line to line. Not all splays had surface expression, whereas almost all surface features had corresponding subsurface expression. As the fault approaches the anticline and multiple splays become apparent, the main fault simply develops into one of a set of splays as the deformation becomes distributed across the wider zone. Eventually, one of the other splays becomes the primary fault strand, and the others are abandoned. [ABSTRACT FROM AUTHOR]

Mixed sand and gravel beaches form a wedge of protective sediment at the base of eroding cliffs. In profile these beaches are typically steep with a prominent storm berm. If the volume of beach sediment is insufficient, storms strip beach sediments seaward, exposing the cliff toe to wave attack. The beach volume is thus crucial to the protection of sea cliffs. In this article we describe a method of calculating alongshore variation in the volume of mixed sand and gravel beaches using ground penetrating radar (GPR). Eighteen sites were studied along 50 km of the east coast of South Island, New Zealand. The method was underpinned by an ability to map the boundary between beach sediments and underlying Pleistocene alluvial-fan sediments. This was achieved by studying the radar facies, particularly landward- dipping overwash deposits and seaward-dipping beach erosion surfaces. The method was ground-truthed in three ways: (1) a stream provided a clean section through one site that was imaged by radar; (2) a storm stripped beach sediment from three sites exposing the substrate, which was then surveyed and compared with radar profiles; (3) excavations in a previous study at nine sites were used to combine the stratigraphy with the radar images. GPR proved highly effective in this environment, revealing thin beaches in the south of the study area that thicken northward in the direction of alongshore sediment transport. Cliff height decreases northward such that there is a transition from beaches in front of cliffs, to beaches that overtop low cliffs, to barriers in front of a coastal lagoon. [ABSTRACT FROM AUTHOR]

Three-dimensional ground-penetrating radar (GPR) data are routinely acquired for diverse geologic, hydrogeologic, archeological, and civil engineering purposes. Interpretations of these data are invariably based on subjective analyses of reflection patterns. Such analyses are heavily dependent on interpreter expertise and experience. Using data acquired across gravel units overlying the Alpine Fault Zone in New Zealand, we demonstrate the utility of various geometric attributes in reducing the subjectivity of 3D GPR data analysis. We use a coherence-based technique to compute the coherency, azimuth, and dip attributes and a gray-level co-occurrence matrix (GLCM) method to compute the texture- based energy, entropy, homogeneity, and contrast attributes. A selection of the GPR attribute volumes allows us to highlight key aspects of the fault zone and observe important features not apparent in the standard images. This selection also provides information that improves our understanding of gravel deposition and tectonic structures at the study site. A new depositional/structural model largely based on the results of our analysis of GPR attributes includes four distinct gravel units deposited in three phases and a well-defined fault trace. This fault trace coincides with a zone of stratal disruption and shearing bound on one side by upward-tilted to synclinally folded stratified gravels and On the other side by moderately dipping stratified alluvial-fan gravels that could have been affected by lateral fault drag. When used in tandem, the coherence- and texture-based attribute volumes can significantly improve the efficiency and quality of 3D GPR interpretation, especially for complex data collected across active fault zones. [ABSTRACT FROM AUTHOR]

Vast sand deposits have accumulated within headland-bound littoral cells along the west coast of Auckland, New Zealand. Integration of different geomorphological data has been used to quantify and interpret the spatial and temporal variability of interannual to interdecadal and longer-term sand storage within the Piha Beach littoral cell. Survey data indicate highly variable and fluctuating deposits of sand moving on and off the active beach face. However, net changes across the cell inferred from aerial photos show shore line advancement of 0.4 to 1.0 m/year since 1940. This represents some 697,400 m3 of sand (121,350 m2 of beach area) added to the onshore beach system in 60 years. Some 12.7 x 106 m3 of sand is estimated to be stored onshore within the Piha cell. Interpretation of stratigraphy and depositional sequences at Piha using ground penetrating radar indicate fluctuating phases of progradation and episodic-transgressive dune activity in the late Holocene. These general patterns at Piha are analogous to those found at other littoral cells along the west coast. [ABSTRACT FROM AUTHOR]

The authors reflect on a coastal monitoring program at Parengarena, a unique site in the extreme north-east of the North Island, New Zealand that began in 1982. Topics discussed include background on the initiation of the program, description of the Parengarena sandspit, and some of the processes and landforms found on the spit.

Dougherty, A.J. and Nichol, S.L., 2007. 3-D Stratigraphic models of a composite barrier system, northern New Zealand. Journal of Coastal Research, SI 50 (Proceedings of the 9th International Coastal Symposium), 922 – 926. Gold Coast, Australia, ISSN 0749-0208 This paper presents for the first time, detailed three-dimensional stratigraphic models of both the Holocene and Pleistocene components of a double barrier using ground-penetrating radar. The study focuses on a composite Quaternary barrier system located in Bream Bay, north-east North Island, New Zealand. This coastal compartment maintains a mesotidal environment with low to moderate wave energy. The Holocene barrier has prograded over the last 6500 years during a relative sea-level still stand, or at most 2 metre fall, resulting in a hummocky dune morphology. In contrast, the Pleistocene barrier was formed during rapid sea-level fall towards the end of the Last Interglacial (oxygen isotope 5e to 5a), which resulted in a forced regression producing linear beach ridges. The sublithified nature of these barrier sediments is conducive to utilising both coring and ground-penetrating radar techniques. This study uses standard sedimentological analysis to ground-truth multiple GPR transects collected over the width of both barriers. This method was employed in order to reconstruct the subsurface stratigraphy in detail and to compare barrier structure over the timescale of successive sea-level highstands. The resulting two- and three-dimensional GPR records all show detailed stratigraphy of a regressive facies succession with similar architecture. However, slight differences in spacing and geometry between beach facies were detected in association with the different dune morphologies from each timeframe. While both beach facies are laterally continuous and dipping in a seaward direction, the Holocene stratigraphy exhibits a more closely-spaced, curvilinear cross-sectional geometry consisting of medium sand and shells; whereas the Pleistocene barrier beachface is highlighted by heavy mineral-rich, fine-grained sands showing a similar concave shape in the large scale, but at a more regularly-spaced interval associated with individual beach ridges. The replication of this stratigraphic form at successive sea-level highstands within the beachface indicates that present-day intermediate nearshore conditions are similar to those of the last interglacial highstand. The overall evolutionary sequence for each barrier differs in width, morphology and stratigraphy due to a combination of factors, including variations in sediment supply, accommodation space, and relative sea level within successive highstands. [ABSTRACT FROM AUTHOR]