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).

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.

At 12.51 pm (NZST) on 22 February 2011 a shallow, magnitude MW 6.2 earthquake with an epicentre located just south of Christchurch, New Zealand, caused widespread devastation including building collapse, liquefaction and landslides. Throughout the Port Hills of Banks Peninsula on the southern fringes of Christchurch landslide and ground damage caused by the earthquake included rock-fall (both cliff collapse and boulder roll), incipient loess landslides, and retaining wall and fill failures. Four deaths from rock-fall occurred during the mainshock and one during an aftershock later in the afternoon of the 22nd. Hundreds of houses were damaged by rock-falls and landslide-induced ground cracking.Four distinct landslide or ground failure types have been recognised. Firstly, rocks fell from lava outcrops on the Port Hills and rolled and bounced over hundreds of metres damaging houses located on lower slopes and on valley floors. Secondly, over-steepened present-day and former sea-cliffs collapsed catastrophically. Houses were damaged by tension cracks on the slopes above the cliff faces and by debris inundation at the toe of the slopes. Thirdly, incipient movement of landslides in loess, ranging from a few millimetres up to 0.35 metres, occurred at several locations. Again houses were damaged by extension fissuring at the head of these features and compressional movement at the toe. The fourth mode of failure observed was retaining wall and fill failures, including shaking-induced settlement and fill displacement. These failures commonly affected both houses and roads.In the days and weeks immediately following the earthquake a major concern was how to manage the risks from another large aftershock or a long return period rainstorm, in the areas worst affected by landslides, should one occur. Each of the four identified landslide types required a different risk management strategy. The rock-fall and boulder roll hazard was managed by identifying buildings at risk and enforcing mandatory evacuation. In the days immediately following the earthquake this process was based on expert opinion. In the weeks after the earthquake this process was rapidly enhanced with empirical data to confirm the risk. The rock-falls associated with cliff collapse were managed by evacuating properties damaged by extensional ground cracking at the top of the cliffs, adjacent properties, and properties damaged by debris inundation at the toe of the cliffs. The incipient landslide hazard was managed by rapidly deploying movement monitoring technologies to determine if these features were still moving and to monitor their response to on-going aftershock activity. The fill and retaining wall failures were managed by encouraging public reporting of areas of concern for rapid assessment by a geotechnical professional.The success of the landslide risk management strategy was demonstrated by the magnitude MW 6.0 earthquake of 13 June when rock-falls and boulder roll damaged evacuated buildings and ground cracking and debris inundation further damaged evacuated areas. Some incipient landslides reactivated, producing similar movement patterns to the 22 February 2011 earthquake. Several retaining walls identified as dangerous and cordoned off also collapsed. No lives were lost and no serious injuries were reported from landslides in the 13 June 2011 earthquake.

On 12 May 2008 at 2.28 pm Beijing Time, an Ms 8.0 earthquake occurred in the Wenchuan County of Sichuan province, China. The associated fault ruptured over 240 km on the ground surface. The resulting damage was very severe and widespread, with casualties of almost 70,000, another 18,000 missing and 370,000 injured. The New Zealand Society for Earthquake Engineering reconnaissance team observed the effects and the recovery from this massive earthquake. The team studied the damages caused to the natural and the built environment due to fault rupture, seismic shaking, huge landslides and rockfalls. Maximum shaking intensity of MM XI significantly exceeded design intensity of MM VII for the area. Earthquake induced landslides had a major and catastrophic impact on development and infrastructure in this earthquake. Site selection was demonstrated to be critical. Brittle or non-ductile and irregular buildings performed very poorly especially in a seismic overload situation. Well engineered structures and dams performed well. Lifeline facilities were severely damaged, which resulted in interruptions to key transportation routes, inhibited rescue and recovery operations.