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This paper describes the performance of log houses in the 2016 Kaikoura earthquake. Most of these houses are in the Mt Lyford village 45 km south-east of Kaikoura.
Typical log houses at Mt Lyford were built using 200mm diameter machined logs. A smaller number of log houses were built with much larger hand-hewn logs of less regular shapes, in traditional log house construction. Most houses were constructed on a concrete slab incorporating the foundations. A small number, especially those on steep sites, had timber poles supporting a timber ground floor platform.
Most of the log houses suffered some lateral movement and subsequent damage. Very few of the houses were damaged beyond repair, and the overall performance was excellent considering the nature of the quake.
One house close to Waiau suffered extreme near-fault shaking, leading to extensive damage, but this is considered to be the result of exceptional ground movement rather than any deficiencies in the design or construction.
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In-field post-earthquake performance observations of winery facilities in the Marlborough region, New Zealand, were documented following the 14 November 2016 Kaikōura earthquake and subsequent aftershocks. Observations presented and discussed herein include land damage to vineyards and the performance of winery building facilities, legged and flat-bedded storage tanks, barrel racking systems, and catwalks. A range of winery facilities were instrumented with tri-axial accelerometers to capture seismic excitations during aftershocks, with the specific aim to instrument different storage tanks having varying capacities and support systems to better understand the dynamic performance and actual forces experienced up the height of the tanks during an earthquake, with preliminary results reported herein.
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The performance of historic buildings during the 14 November 2016 Mw7.8 Kaikoura, New Zealand earthquake is reported, focusing on early stone and clay brick masonry buildings, vintage concrete structures, cob cottages, and the non-structural masonry chimneys and veneers of buildings located in the upper part of the South Island (Marlborough and North Canterbury regions). To better document structural response, the intensity of horizontal and vertical ground motion from the nearest recording station is graphically placed alongside the assessed level of damage. In response to numerous strong earthquakes that have previously occurred in the area a large number of highly vulnerable buildings or non-structural building components were previously either seismically retrofitted or demolished, thereby reducing the level of damage and loss of life during the 2016 Kaikoura earthquake. Seismically retrofitted stone and clay brick masonry buildings and cob cottages exhibited good performance, while some vintage concrete structures and partially strengthened cob cottages suffered moderate to extensive levels of damage. A large stock of URM chimneys in Picton, Seddon and Rotherham were previously removed while in other locations chimneys presented a variety of responses. Rural masonry veneer dwellings located in Seddon and Waiau experienced high damage levels, typically resulting in out-of-plane collapse of the masonry veneer.
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This paper describes the damage to non-structural elements in buildings following the 14th November 2016 Kaikōura earthquake. As has been observed in recent earthquakes in New Zealand and around the world, damage to non-structural elements is a major contributor to overall building damage. This paper focusses on damage to non-structural elements in multi-storey commercial buildings, in particular damage to the following: suspended ceilings, suspended services, glazing, precast panels, internal linings, seismic gaps and contents. The nature and extent of damage to each of these components is discussed in this paper with the help of typical damage photos taken after the earthquake. The paper also presents observations on the seismic performance of non-structural elements where seismic bracing was present. These observations suggest that seismic bracing is an effective means to improve seismic performance of non-structural elements.
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The 2016 Kaikoura earthquake resulted in shaking in excess of design level demands for buildings with periods of 1-2s at some locations in Wellington. This period range correlated to concrete moment frame buildings of 5-15 storeys, many of which had been built in Wellington since the early 1980s, and often with precast concrete floor units. The critical damage states used to assess buildings during the Wellington City Council Targeted Assessment Programme are described and examples of observed damage correlating to these damage states are presented. Varying degrees of beam hinging were observed, most of which are not expected to reduce the frame capacity significantly. Buildings exhibiting varying degrees of residual beam elongation were observed. Cases of significant beam elongation and associated support beam rotation resulted in damage to precast floor unit supports; in one case leading to loss of support for double-tee units. The deformation demands also resulted in damage to floor diaphragms, especially those with hollowcore floor units. Cracking in floor diaphragms was commonly concentrated in the corners of the building, but hollowcore damage was observed both at the corners and in other locations throughout several buildings. Transverse cracking of hollowcore floor units was identified as a particular concern. In some cases, transverse cracks occurred close to the support, as is consistent with previous research on hollowcore floor unit failure modes. However, transverse cracks were also observed further away from the support, which is more difficult to assess in terms of severity and residual capacity. Following the identification of typical damage, attention has shifted to assessment, repair, and retrofit strategies. Additional research may be required to determine the reduced capacity of cracked hollowcore floor units and verify commonly adopted repair and retrofit strategies.
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Widespread liquefaction occurred in the end-dumped gravelly fills and hydraulically-placed dredged sandy fill at the CentrePort of Wellington as a result of the 14 November 2016 Mw7.8 Kaikoura earthquake. This liquefaction resulted in substantial global (mass) settlement and lateral movement (spreading) of the fills towards the sea, which adversely affected wharf structures and buildings constructed on shallow and deep foundations. This paper presents key observations from the QuakeCoRE-GEER post-earthquake reconnaissance efforts at the CentrePort Wellington. The different materials and methods used to construct the reclaimed land at CentrePort influenced the patterns of observed liquefaction and its effects. Areas of gravel liquefaction at the port are especially important due to the limited number of these case histories in the literature. Liquefaction-induced ground deformations caused the wharves to displace laterally and damage their piles and offloading equipment. Lateral ground extension and differential settlement damaged buildings, whereas buildings in areas of uniform ground settlement without lateral extension performed significantly better.
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Although located about 200 km away from the epicentre of the 2016 Kaikōura Earthquake, the waterfront areas of Wellington City suffered varying degrees of damage as a result of soil liquefaction and associated ground deformations. This paper presents a summary of the major observations made following reconnaissance inspections of the geotechnical effects caused by the earthquake, with emphasis on the ground performance in the affected areas near the waterfront. Except for CentrePort, summarised elsewhere in this Special Issue, the inspections concentrated mostly on the waterfront areas and the impact to buildings built on reclaimed lands. Cracks and minor ground subsidence were observed in many parts of the waterfront, but the damage was less than that in CentrePort where significant liquefaction-induced damage was evident. The age of reclamation appears to have significant effect on the distribution of liquefaction-induced damage, while reclaimed areas where improvement techniques have been implemented performed well.
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The magnitude Mw7.8 ‘Kaikōura’ earthquake occurred shortly after midnight on 14 November 2016. This paper presents an overview of the geotechnical impacts on the South Island of New Zealand recorded during the post-event reconnaissance.
Despite the large moment magnitude of this earthquake, relatively little liquefaction was observed across the South Island, with the only severe manifestation occurring in the young, loose alluvial deposits in the floodplains of the Wairau and Opaoa Rivers near Blenheim. The spatial extent and volume of liquefaction ejecta across South Island is significantly less than that observed in Christchurch during the 2010-2011 Canterbury Earthquake Sequence, and the impact of its occurrence to the built environment was largely negligible on account of the severe manifestations occurring away from the areas of major development.
Large localised lateral displacements occurred in Kaikōura around Lyell Creek. The soft fine-grained material in the upper portions of the soil profile and the free face at the creek channel were responsible for the accumulation of displacement during the ground shaking. These movements had severely impacted the houses which were built close (within the zone of large displacement) to Lyell Creek. The wastewater treatment facility located just north of Kaikōura also suffered tears in the liners of the oxidation ponds and distortions in the aeration system due to ground movements.
Ground failures on the Amuri and Emu Plains (within the Waiau Valley) were small considering the large peak accelerations (in excess of 1g) experienced in the area. Minor to moderate lateral spreading and ejecta was observed at some bridge crossings in the area. However, most of the structural damage sustained by the bridges was a result of the inertial loading, and the damage resulting from geotechnical issues were secondary.
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Tens of thousands of landslides were generated over 10,000 km2 of North Canterbury and Marlborough as a consequence of the 14 November 2016, Mw7.8 Kaikōura Earthquake. The most intense landslide damage was concentrated in 3500 km2 around the areas of fault rupture. Given the sparsely populated area affected by landslides, only a few homes were impacted and there were no recorded deaths due to landslides. Landslides caused major disruption with all road and rail links with Kaikōura being severed. The landslides affecting State Highway 1 (the main road link in the South Island of New Zealand) and the South Island main trunk railway extended from Ward in Marlborough all the way to the south of Oaro in North Canterbury.
The majority of landslides occurred in two geological and geotechnically distinct materials reflective of the dominant rock types in the affected area. In the Neogene sedimentary rocks (sandstones, limestones and siltstones) of the Hurunui District, North Canterbury and around Cape Campbell in Marlborough, first-time and reactivated rock-slides and rock-block slides were the dominant landslide type. These rocks also tend to have rock material strength values in the range of 5-20 MPa. In the Torlesse ‘basement’ rocks (greywacke sandstones and argillite) of the Kaikōura Ranges, first-time rock and debris avalanches were the dominant landslide type. These rocks tend to have material strength values in the range of 20-50 MPa.
A feature of this earthquake is the large number (more than 200) of valley blocking landslides it generated. This was partly due to the steep and confined slopes in the area and the widely distributed strong ground shaking. The largest landslide dam has an approximate volume of 12(±2) M m3 and the debris from this travelled about 2.7 km2 downslope where it formed a dam blocking the Hapuku River. The long-term stability of cracked slopes and landslide dams from future strong earthquakes and large rainstorms are an ongoing concern to central and local government agencies responsible for rebuilding homes and infrastructure. A particular concern is the potential for debris floods to affect downstream assets and infrastructure should some of the landslide dams breach catastrophically.
At least twenty-one faults ruptured to the ground surface or sea floor, with these surface ruptures extending from the Emu Plain in North Canterbury to offshore of Cape Campbell in Marlborough. The mapped landslide distribution reflects the complexity of the earthquake rupture. Landslides are distributed across a broad area of intense ground shaking reflective of the elongate area affected by fault rupture, and are not clustered around the earthquake epicentre. The largest landslides triggered by the earthquake are located either on or adjacent to faults that ruptured to the ground surface. Surface faults may provide a plane of weakness or hydrological discontinuity and adversely oriented surface faults may be indicative of the location of future large landslides. Their location appears to have a strong structural geological control. Initial results from our landslide investigations suggest predictive models relying only on ground-shaking estimates underestimate the number and size of the largest landslides that occurred.
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This paper presents ground motion and site effect observations in the greater Wellington region from the 14 November 2016 Mw7.8 Kaikōura earthquake. The region was the principal urban area to be affected by the earthquake-induced ground motions from this event. Despite being approximately 60km from the northern extent of the causative earthquake rupture, the ground motions in Wellington exhibited long period (specifically T = 1 - 3s) ground motion amplitudes that were similar to, and in some locations exceeded, the current 500 year return period design ground motion levels. Several ground motion observations on rock provide significant constraint to understand the role of surficial site effects in the recorded ground motions. The largest long period ground motions were observed in the Thorndon and Te Aro basins in Wellington City, inferred as a result of 1D impedance contrasts and also basin-edge-generated waves. Observed site amplifications, based on response spectral ratios with reference rock sites, are seen to significantly exceed the site class factors in NZS1170.5:2004 for site class C, D, and E sites at approximately T=0.3-3.0s. The 5-95% Significant Duration, Ds595, of ground motions was on the order of 30 seconds, consistent with empirical models for this earthquake magnitude and source-to-site distance. Such durations are slightly longer than the corresponding Ds595 = 10s and 25s in central Christchurch during the 22 February 2011 Mw6.2 and 4 September 2010 Mw7.1 earthquakes, but significantly shorter than what might be expected for large subduction zone earthquakes that pose a hazard to the region. In summary, the observations highlight the need to better understand and quantify basin and near-surface site response effects through more comprehensive models, and better account for such effects through site amplification factors in design standards.
