“The San Andreas Fault, being on the opposite side of the Pacific plate, it is like our distant brother or whanau — family,” said Langridge. Numerous experts say it will be the largest natural disaster of modern times in New Zealand. “One of the outcomes of this study is that you should expect a shorter recurrence interval of strong shaking at fault section ends,” Langridge said. The Alpine fault is the longest active fault in NZ, measuring more than 600 km long, with the largest average long term slip rate (Yetton, 2000). If the Alpine Fault does trigger another magnitude 8-plus quake in the near future, GNS says it will "have a major impact on the lives of many people", and likely be "one of the biggest earthquakes since European settlement of New Zealand". The most recent earthquake could represent a “partial-section” rupture of only the central portion of the Alpine fault, a rupture of the fault’s northern section that continued southwest into the central segment, or even triggered slip from a rupture along the nearby Marlborough Fault System. The events were confirmed by data collected from other nearby trenching sites and from geological deposits called turbidites, which are sediments shaken loose into a body of water by seismic activity, in lakes along the central section of the Alpine fault. Alpine Fault Geometry and Physical Properties at Depth. Together these sites revealed evidence of 27 Alpine Fault earthquakes over the last 8000 years! "Given what we know from geological studies of the Alpine Fault, we're anticipating a major magnitude 8.0-plus earthquake, rupturing 500km of the crust, so the shaking will be felt throughout the South Island, but the intensity and duration will ultimately depend on what happens on the fault." Note: The above post is reprinted from materials provided by Seismological Society of America. The Alpine Fault is sometimes compared with California’s San Andreas Fault, being another fast-moving strike slip fault near a plate boundary. After trenching along the fault at the Staples site near the Toaroha River, however, Robert Langridge of GNS Science and colleagues uncovered evidence of a more recent earthquake along the northeastern end of the fault’s central portion. The Alpine Fault runs 400km up the South Island, along the western edge of the Southern Alps. The investigation found the mean interval between large earthquakes on the fault is 330 years and two thirds of the intervals were between 260 and 400 years. Recent research has found that the average time between large earthquakes on the fault is 330 years. Simulation shows widespread damage if Alpine Fault ruptures, 'What was that?!' It runs as a single structure for over 500 km. The findings published in the Bulletin of the Seismological Society of America suggest that some places along the fault, particularly around the towns of Hokitika and Greymouth, could experience strong ground shaking from Alpine fault earthquakes more often than previously thought. There have been no major historical earthquakes on the Alpine Fault. High Heat Flow and Geothermal Gradient. But Dr Langridge and colleagues have now confirmed smaller quakes can happen on the fault in between the big ones. The effect of fluid differentials on an Alpine Fault earthquake is obviously significant but presently unquantified. Because of this during the mid 20th century it was speculated that the Alpine Fault creeps without making large earthquakes. A new model has simulated the disruption a major Alpine Fault earthquake would have on the South Island's transport network - cutting off the West Coast for at least a week. How will the next Alpine Fault earthquake compare to the M7.1 Darfield earthquake of 4 September 2010? How often does the Alpine Fault cause earthquakes? But there has been as little as 140 years and as much as 510 years between Alpine fault earthquakes. However, the plates are locked and when they overcome these barriers, they produce large but … Alpine Fault Dynamic Rupture Model. The length of the rupture will be up to 400 km, eg. The fault, which runs about 600km up the western side of the South Island between Milford Sound and Marlborough, poses one of the biggest natural threats to New Zealand - especially the West Coast, Canterbury and Otago. For every one unit increase in magnitude (e.g. Last year, GNS Science earthquake scientist Rob Langridge and Victoria University paleoseismologist Jamie Howarth uncovered evidence of a previously unknown quake that took place sometime between 1740 and 1840. Robert M. Langridge, Pilar Villamor, Jamie D. Howarth, William F. Ries, Kate J. Clark, Nicola J. Litchfield. Credits: Video - Newshub; Image - NASA/file. But new evidence of a 19th century earthquake indicates that in at least one portion of the fault, smaller earthquakes may occur in between such large rupture events. Research has found a big one happens every 300 years or so, and GNS Science estimates there's about a 30 percent chance of another happening in the next 50 years. Alternatively, the quake might have been centred further north, the rupture spreading along the fault to the southwest where Dr Langridge and his team did their digging; or possibly triggered by a separate quake in the Marlborough Fault System. The Alpine Fault is sometimes compared with California's San Andreas Fault, being another fast-moving strike slip fault near a plate boundary. Radiocarbon dating places this earthquake between 1813 and 1848. Reference: Analysis of tree ring patterns in 2018 suggested it happened in 1717, prior to European settlement when there were few people in the South Island. Evidence is growing the South Island's Alpine Fault, capable of devastating earthquakes of magnitude 8 and above, ruptures more frequently than previously believed. The earthquake will last for about two minutes. The Alpine Fault • Running about 600km up the spine of the South Island, the Alpine Fault is the boundary of the Pacific and Australian tectonic plates. The Alpine Fault is overdue for an earthquake that could reshape the South Island, scientists say. Because of the recurrence times of earthquakes though, you obviously have to wait a long time to see the effects of such fault behavior.". An Alpine Fault earthquake will be felt by every South Islander and likely many North Islanders, too. (2014) reported the probability of occurrence of an Alpine Fault Magnitude 8 earthquake in the next 50 years as 30%, resulting in an estimated $10 billion in economic cost. In between earthquakes, the Alpine Fault is locked. It is very difficult to predict whether an Alpine Fault earthquake could trigger any activity on the Marlborough Fault System and the Hikurangi Subduction Zone, but it is highly unlikely that a single earthquake could rupture right through from the Alpine Fault to the Hikurangi Subduction Zone. This is not a regular pattern, but enough to suggest there is a high probability of a large earthquake in the next 50 years. However, the findings do suggest that seismic activity on the Alpine Fault is more complex than suspected, particularly along its northern reaches where the plate boundary transitions into another fault zone. A rupture along the full length of the fast-slipping Alpine Fault on New Zealand’s South Island poses the largest potential seismic threat to the southern and central parts of the country. The 2012 paper suggests simply that fault zones are sites of high fluid pressure gradient, and that “dynamic pressurisation likely promotes earthquake slip.” Stage two of the deep-drilling programme is scheduled for 2014. The science While we can’t predict when earthquakes will occur, scientific research has shown that the Alpine Fault has a regular history of producing large earthquakes. At John O'Groats, core samples showed layers similar to those found at Hokuri Creek. Reconciling an Early Nineteenth-Century Rupture of the Alpine Fault at a Section End, Toaroha River, Westland, New Zealand. "Once we started working there, the story really grew in large part because of the richness of dateable organic material in the trenches.". Large earthquakes are less common along the central Alpine Fault, where the plates are not subducting and the forces are accommodated in different ways. All these cities have experienced severe earthquakes since European settlement. Discussion: Alpine Fault Rupture Mechanisms. In the past ~1000 years there have been four large earthquakes on the Alpine Fault and two large … The alpine fault earthquake will alter tectonic stress distribution, and other faultlines may rupture in the days or years following it. The 100-metre and 150-metre probes of stage one were … This fault has suddenly moved or ruptured four times in the past 900 years, each time causing an earthquake of about magnitude 8. The last such earthquake took place in 1717. Some studies looking 100 years out have concluded it's as much as 85 percent likely. The Alpine Fault is the dominant structure defining the Australian-Pacific plate boundary in the South Island of New Zealand. "An important outcome is that sites or towns near fault intersections and section ends may experience strong ground motions more frequently due to locally shorter rupture recurrence intervals," the study, published in the Bulletin of the Seismological Society of America this week, says. It has ruptured four times in the last 900 years, resulting in earthquakes of around magnitude 8, and is now considered highly probable to go again in the next 50 years. The four most recent earthquakes uncovered by the researchers at the site range in dates from 1084 to 1848. This means, for instance, that an Alpine Fault earthquake of M8.1 would release about 30 times more energy that the Darfield earthquake of M7.1. Langridge said researchers in California and New Zealand have a long history of earthquake science collaboration and are learning from each other about the treatment of active faults and fault segmentation for seismic hazard models. from M4 to M5) there is about a 30-fold increase in energy release. This is more recent than the 1717 quake, which has been estimated at magnitude 8.1 - nearly three times stronger than the 2016 Kaikoura earthquake - and shifted one side 8m relative to the other. And the towns of Hokitika and Greymouth are sitting right in the firing line. The Alpine Fault is one of the world's major plate boundaries and New Zealand's most hazardous earthquake-generating fault. Recent research by GNS Science has extended our knowledge of the Alpine fault earthquake record back through the past 8,000 years. The rupture will produce one of the biggest earthquakes since European settlement of New Zealand, and it will have a major impact on the lives of many people. The South Island Alpine Fault Earthquake Response (SAFER) Framework provides a concept of coordination of response and priority setting across all six South Island Civil Defence Emergency Management (CDEM) Groups and their partner organisations in the first seven days of response. The Alpine Fault has a high probability (estimated at 30%) of rupturing in the next 50 years. An Alpine Fault earthquake will likely rupture … on Haast and spreading north to Ahaura. The largest city within the highest-risk zone is the nation's capital, Wellington, followed by Hastings then Napier. The best paleoseismic evidence to date suggests the southern and central sections of the Alpine Fault, at the boundary separating the Australian and Pacific tectonic plates, typically rupture during very large full-section earthquakes of magnitude 7.7 or larger. “One of the real challenges with the Alpine Fault — because it is so bush-covered — is actually finding sites that have been cleared and therefore can be studied,” said Langridge. The last major earthquake on the Alpine Fault was in 1717, so we're already a little overdue for one of the biggest earthquakes in New Zealand's modern history. The best paleoseismic evidence to date suggests the southern and central sections of the Alpine Fault, at the boundary separating the Australian and Pacific tectonic plates, typically rupture during very large full-section earthquakes of magnitude 7.7 or larger. Langridge said researchers in California and New Zealand have a long history of earthquake science collaboration and are learning from each other about the treatment of active faults and fault segmentation for seismic hazard models. The 19th century quake was perhaps only a partial-section slip, Dr Langridge said, proving activity on the Alpine Fault is more complex than previously thought - particularly in its north, where it meets up with other fault zones, such as the Marlborough Fault System. There isn't enough evidence yet to favour one scenario over the others, Dr Langridge said. Using techniques like these, scientists such as Mark Yetton of the University of Canterbury have found out that major earthquakes happened on the central Alpine Fault in 1100, 1450, 1620 and 1717. The Alpine Fault is a geological fault, known as a right-lateral strike-slip fault, that runs almost the entire length of New Zealand's South Island. Bulletin of the Seismological Society of America, 2020; DOI: 10.1785/0120200116. However, it is now inferred by multiples lines of evidence that the Alpine Fault ruptures creating major earthquakes about every few hundred years. 7.4 magnitude quake hits off NZ's coast, Kiwis warned to stay out of water, The South Island regions an Alpine Fault quake would affect most, Alpine Fault overdue for magnitude 8+ quake - scientists, Copyright © 2020 MediaWorks TV - All Rights Reserved, By subscribing you agree to our Terms of Access and Privacy Policy, uncovered evidence of a previously unknown quake. Project AF8 is a collaborative effort to prepare for a magnitude 8 Alpine Fault earthquake. Evidence for Ancient Alpine Fault Earthquakes. In addition to the newly discovered quake, they found more evidence for three big quakes - one between 1084 and 1276, a second between 1250 and 1580, and the most recent big one, which they dated to between 1673 and 1792. Alpine Fault Locking Inferred from Geodetic Data. It forms the sharp line separating the snow-covered Southern Alps in the east from the low coastal plain bordering the Tasman Sea in the west. But the findings prove there could be strong quakes on the fault in between the big ones. The last such earthquake took place in 1717. As with many natural systems, there was a spread of intervals with the longest being about 510 years and the … Scientists trenched a site near the Toaroha River, south of Hokitika, and found evidence of the more recent quake in the northern part of the 600km-long fault's central section. New Zealand earthquakes cause total DEVASTATION The Alpine Fault runs right through the heart of New Zealand's glacier county on the country's south island. Langridge and colleagues said that there isn’t enough evidence yet to favor one of these scenarios over the others. Related video: Alpine Fault overdue for magnitude 8+ quake - scientists. Discussion: Maximum Earthquake Magnitude. The next Alpine Fault earthquake would likely also be a long-duration event – unzipping the crust for as much as three minutes - because of the sheer length of the fault. During the field trip follow the line of the Alpine Fault as it is crossed by roads, bridges, rivers, mountains, power lines, and phone lines from Arthur's Pass to Whataroa on the West Coast. Deep low-frequency earthquakes indicate migration of magmatic fluids beneath Laacher See... Alaska Centennial Nugget : Largest Gold Nugget Ever Found in Alaska, New source of energy-critical lithium found in supervolcanoes, Marine life recovery following the dinosaurs’ extinction, New trilobite fossil reveals cephalic specialization of trilobites in Middle Cambrian. The mid 20th century it was speculated that the average time between large earthquakes the... Compared with California ’ s San Andreas Fault, being another fast-moving strike slip near... 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