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59-589: The Otago fault system (also known as Otago reverse fault province ) contains multiple faults with the potential to have rupture events greater than M w 7 in magnitude. These are parallel to, and to the east of the Alpine Fault in the south eastern part of the South Island of New Zealand . It accommodates about 2 mm (0.079 in)/year of contraction. East of the Southern Alps , Central Otago has

118-494: A complex form of the Love wave which, although a surface wave, he found provided a result more closely related to the mb  scale than the M s   scale. Lg waves attenuate quickly along any oceanic path, but propagate well through the granitic continental crust, and Mb Lg is often used in areas of stable continental crust; it is especially useful for detecting underground nuclear explosions. Surface waves propagate along

177-401: A different scaling and zero point. K values in the range of 12 to 15 correspond approximately to M 4.5 to 6. M(K), M (K) , or possibly M K indicates a magnitude M calculated from an energy class K. Earthquakes that generate tsunamis generally rupture relatively slowly, delivering more energy at longer periods (lower frequencies) than generally used for measuring magnitudes. Any skew in

236-612: A few thousand years before moving on to another fault system. Such episodic earthquake activity is thought to be the result of strain sharing between faults within the system. There is now good evidence for this. The most recent active faults moving from the north east towards the south are the Ostler Fault Zone and Lewis Pass faults, although these are mainly in Canterbury, the NW Cardrona Fault (and its northern continuation of

295-680: A fifth of the currently 10 mm (0.39 in) /year compression element is taken up by the Otago fault system in mainly the Permian Ophiolite Belt and Otago schists in the Otago range and basin province. This Otago peneplain lies between the Southland Syncline and the Canterbury Plains . The consequence appears to be long periods of inactivity on individual reverse faults, perhaps 100,000 years and then multiple release events over

354-684: A lowercase " l ", either M l , or M l . (Not to be confused with the Russian surface-wave MLH scale. ) Whether the values are comparable depends on whether the local conditions have been adequately determined and the formula suitably adjusted. In Japan, for shallow (depth < 60 km) earthquakes within 600 km, the Japanese Meteorological Agency calculates a magnitude labeled MJMA , M JMA , or M J . (These should not be confused with moment magnitudes JMA calculates, which are labeled M w (JMA) or M , nor with

413-675: A number of parallel, northeast trending ranges separating broad, flat-bottomed valleys which extend to the coast of Otago . These ranges are associated with the main reverse faults of the system. Near the Southern Alps the faults with this north-east trend continue through Lindis Pass into South Canterbury and so the Dalrachney/Lindis Pass Fault and the Ostler Fault Zone in South Canterbury are geologically related to

472-408: A small settlement on the site in 1843 and Maori were still living here in 1850. An early European settler was a former whaler, 'The Hermit of Taieri Mouth' (also known as John Bull) whose real name was John Edward O'Neil. He is remembered for his boisterous ways and prodigious strength. On 4 July 2024 the area saw the finding of a deceased intact 5 metres (16 ft) male blackish-silver specimen of

531-432: A wave, such as its timing, orientation, amplitude, frequency, or duration. Additional adjustments are made for distance, kind of crust, and the characteristics of the seismograph that recorded the seismogram. The various magnitude scales represent different ways of deriving magnitude from such information as is available. All magnitude scales retain the logarithmic scale as devised by Charles Richter , and are adjusted so

590-399: Is "approximately related to the released seismic energy." Intensity refers to the strength or force of shaking at a given location, and can be related to the peak ground velocity. With an isoseismal map of the observed intensities (see illustration) an earthquake's magnitude can be estimated from both the maximum intensity observed (usually but not always near the epicenter ), and from

649-401: Is actually a surface-wave magnitude. Other magnitude scales are based on aspects of seismic waves that only indirectly and incompletely reflect the force of an earthquake, involve other factors, and are generally limited in some respect of magnitude, focal depth, or distance. The moment magnitude scale – Mw or M w – developed by seismologists Thomas C. Hanks and Hiroo Kanamori ,

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708-500: Is based on an earthquake's seismic moment , M 0 , a measure of how much work an earthquake does in sliding one patch of rock past another patch of rock. Seismic moment is measured in Newton-meters (Nm or N·m ) in the SI system of measurement, or dyne-centimeters (dyn-cm; 1 dyn-cm = 10 Nm ) in the older CGS system. In the simplest case the moment can be calculated knowing only

767-594: Is close to the small towns of Hyde and Middlemarch . The last four surface-rupturing earthquakes occurred about 47,000 years ago, 39,000 years ago, 23,000 years ago and 10,300 years ago. Movement along it has built up the Rock and Pillar Range to 1,200 m (3,900 ft) above the valley floor. Its current slip rate has been recently updated to be 0.24 mm (0.0094 in)/year. 45°24′S 169°36′E  /  45.4°S 169.6°E  / -45.4; 169.6 Seismic magnitude scales#Mw The Earth's crust

826-504: Is dissipated as friction (resulting in heating of the crust). An earthquake's potential to cause strong ground shaking depends on the comparatively small fraction of energy radiated as seismic waves, and is better measured on the energy magnitude scale, M e . The proportion of total energy radiated as seismic waves varies greatly depending on focal mechanism and tectonic environment; M e   and M w   for very similar earthquakes can differ by as much as 1.4 units. Despite

885-505: Is measured at periods of up to 30 seconds. The regional mb Lg scale – also denoted mb_Lg , mbLg , MLg (USGS), Mn , and m N – was developed by Nuttli (1973) for a problem the original M L scale could not handle: all of North America east of the Rocky Mountains . The M L scale was developed in southern California, which lies on blocks of oceanic crust, typically basalt or sedimentary rock, which have been accreted to

944-436: Is stressed by tectonic forces. When this stress becomes great enough to rupture the crust, or to overcome the friction that prevents one block of crust from slipping past another, energy is released, some of it in the form of various kinds of seismic waves that cause ground-shaking, or quaking. Magnitude is an estimate of the relative "size" or strength of an earthquake , and thus its potential for causing ground-shaking. It

1003-523: Is the mantle magnitude scale, M m . This is based on Rayleigh waves that penetrate into the Earth's mantle, and can be determined quickly, and without complete knowledge of other parameters such as the earthquake's depth. M d designates various scales that estimate magnitude from the duration or length of some part of the seismic wave-train. This is especially useful for measuring local or regional earthquakes, both powerful earthquakes that might drive

1062-655: The 2018 New Zealand census , an increase of 57 people (29.2%) since the 2013 census , and an increase of 63 people (33.3%) since the 2006 census . There were 108 households, comprising 132 males and 123 females, giving a sex ratio of 1.07 males per female. The median age was 52.8 years (compared with 37.4 years nationally), with 39 people (15.5%) aged under 15 years, 18 (7.1%) aged 15 to 29, 123 (48.8%) aged 30 to 64, and 72 (28.6%) aged 65 or older. Ethnicities were 95.2% European/ Pākehā , 10.7% Māori , 1.2% Pasifika , and 3.6% other ethnicities. People may identify with more than one ethnicity. Although some people chose not to answer

1121-625: The Hunter Valley Fault and southern continuation as the Nevis and West Nokomai faults. At the coast the Settlement Fault (essentially in Southland but part of the Otago fault system) and Akatore Fault are the most recently active. The expectation over the whole fault system is a rupture every 100 to 200 years of an earthquake between magnitude 6.5 to 7. Because of the good evidence that some of

1180-563: The Shindo intensity scale .) JMA magnitudes are based (as typical with local scales) on the maximum amplitude of the ground motion ; they agree "rather well" with the seismic moment magnitude M w   in the range of 4.5 to 7.5, but underestimate larger magnitudes. Body-waves consist of P waves that are the first to arrive (see seismogram), or S waves , or reflections of either. Body-waves travel through rock directly. The original "body-wave magnitude" – mB or m B (uppercase "B") –

1239-681: The Southern Scenic Route . It is located in the Clutha District on the boundary of Dunedin City and 10 kilometres (6.2 mi) east of Lake Waihola . Immediately to its south is the smaller settlement of Taieri Beach, and the two are often considered parts of the same settlement. It gained a little notoriety or sadness in the 1990s, relating to the Bain family murders , as the place where Robin Bain worked as

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1298-569: The Taieri Plain by Lake Waihola . Tuwiriroa had a daughter Haki Te Kura, famous for swimming across Lake Wakatipu . Tukiauau had a handsome son Korokiwhiti. The daughter and son now fell in love but the woman's father, the chief of the Taieri Mouth pa, disapproved. The young man's father was a hunted man. Hearing his enemies had discovered his whereabouts he decided to abandon the upriver settlement and move his people further south. As they came down

1357-562: The Earth's surface, and are principally either Rayleigh waves or Love waves . For shallow earthquakes the surface waves carry most of the energy of the earthquake, and are the most destructive. Deeper earthquakes, having less interaction with the surface, produce weaker surface waves. The surface-wave magnitude scale, variously denoted as Ms , M S , and M s , is based on a procedure developed by Beno Gutenberg in 1942 for measuring shallow earthquakes stronger or more distant than Richter's original scale could handle. Notably, it measured

1416-625: The IASPEI in 1967; this is the basis of the standardized M s20 scale (Ms_20, M s (20)). A "broad-band" variant ( Ms_BB , M s (BB) ) measures the largest velocity amplitude in the Rayleigh-wave train for periods up to 60 seconds. The M S7 scale used in China is a variant of M s calibrated for use with the Chinese-made "type 763" long-period seismograph. The MLH scale used in some parts of Russia

1475-405: The Otago fault system. The last partial rupture was about 18,000 years ago and single event displacements are about 3.5 m (11 ft). The recent activity implies a slip rate of 0.15 mm (0.0059 in)/year with recurrence average of 19,000 years. The fault is named for the rural locality of Titri, close to the eastern shore of Lake Waihola . The Kaikorai Fault is well mapped through

1534-617: The Otago fault system. Otago, towards the coast, is separated from South Canterbury by the Waitaki River and the south western aspect of this river valley is defined by mainly normal north-northwest striking faults such as the Hawkdun Fault , and Waihemo fault zone . The south eastern part of the zone is limited by Fiordland and the Hillfoot Fault in Southland which is a reverse fault on

1593-587: The Otago side of the Hokonui Hills and The Catlins . Just off the coast from Dunedin towards the south are several active northeast-trending faults of the system. The boundary between the Australian and Pacific plates passes through the west of the South Island of New Zealand, as the very active by world standards, Alpine Fault . While this takes up a major part of the movement across these plate boundaries,

1652-417: The almost unknown Mesoplodon traversii (spade-toothed whale) was washed ashore. Taieri Mouth is described by Statistics New Zealand as a rural settlement. It covers 3.25 km (1.25 sq mi), and had an estimated population of 290 as of June 2024, with a population density of 89 people per km . It is part of the much larger Bruce statistical area . Taieri Mouth had a population of 252 at

1711-452: The amount of slip, the area of the surface ruptured or slipped, and a factor for the resistance or friction encountered. These factors can be estimated for an existing fault to determine the magnitude of past earthquakes, or what might be anticipated for the future. An earthquake's seismic moment can be estimated in various ways, which are the bases of the M wb , M wr , M wc , M ww , M wp , M i , and M wpd scales, all subtypes of

1770-426: The amplitude of surface waves (which generally produce the largest amplitudes) for a period of "about 20 seconds". The M s   scale approximately agrees with M L   at ~6, then diverges by as much as half a magnitude. A revision by Nuttli (1983) , sometimes labeled M Sn , measures only waves of the first second. A modification – the "Moscow-Prague formula" – was proposed in 1962, and recommended by

1829-549: The body-wave (mb ) or the seismic energy (M e  ) is there a difference comparable to the difference in damage. Rearranged and adapted from Table 1 in Choy, Boatwright & Kirby 2001 , p. 13. Seen also in IS 3.6 2012 , p. 7. K (from the Russian word класс, 'class', in the sense of a category ) is a measure of earthquake magnitude in the energy class or K-class system, developed in 1955 by Soviet seismologists in

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1888-476: The census's question about religious affiliation, 54.8% had no religion, 29.8% were Christian , 1.2% had Māori religious beliefs and 1.2% had other religions. Of those at least 15 years old, 36 (16.9%) people had a bachelor's or higher degree, and 57 (26.8%) people had no formal qualifications. The median income was $ 28,000, compared with $ 31,800 nationally. 15 people (7.0%) earned over $ 70,000 compared to 17.2% nationally. The employment status of those at least 15

1947-523: The continent. East of the Rockies the continent is a craton , a thick and largely stable mass of continental crust that is largely granite , a harder rock with different seismic characteristics. In this area the M L scale gives anomalous results for earthquakes which by other measures seemed equivalent to quakes in California. Nuttli resolved this by measuring the amplitude of short-period (~1 sec.) Lg waves,

2006-472: The continental crust. All these problems prompted the development of other scales. Most seismological authorities, such as the United States Geological Survey , report earthquake magnitudes above 4.0 as moment magnitude (below), which the press describes as "Richter magnitude". Richter's original "local" scale has been adapted for other localities. These may be labelled "ML", or with

2065-399: The correlation can be reversed to predict tidal height from earthquake magnitude. (Not to be confused with the height of a tidal wave, or run-up , which is an intensity effect controlled by local topography.) Under low-noise conditions, tsunami waves as little as 5 cm can be predicted, corresponding to an earthquake of M ~6.5. Another scale of particular importance for tsunami warnings

2124-515: The course of the railway line south, and is associated with the coastal hills to its east and the Titri anticline. Some believe it may extend all the way to the Water of Leith . It was originally a normal fault with displacement to the southeast over 100 million years ago. It was reactivated perhaps 40,000 years ago with reversal of movement which has formed the coastal hills in the typical northeast orientation of

2183-501: The duration of shaking. This is why, in the 1989 Loma Prieta earthquake , the Marina district of San Francisco was one of the most damaged areas, though it was nearly 100 km from the epicenter. Geological structures were also significant, such as where seismic waves passing under the south end of San Francisco Bay reflected off the base of the Earth's crust towards San Francisco and Oakland. A similar effect channeled seismic waves between

2242-460: The duration or amplitude of a part of the seismic wave, the coda . For short distances (less than ~100 km) these can provide a quick estimate of magnitude before the quake's exact location is known. Taieri Mouth Taieri Mouth is a small fishing village at the mouth of the Taieri River , New Zealand . Taieri Island (Moturata) lies in the ocean several hundred metres off

2301-401: The extent of the area where the earthquake was felt. The intensity of local ground-shaking depends on several factors besides the magnitude of the earthquake, one of the most important being soil conditions. For instance, thick layers of soft soil (such as fill) can amplify seismic waves, often at a considerable distance from the source, while sedimentary basins will often resonate, increasing

2360-461: The faults in the system can have large periods of quiescence, the information that follows should be supplemented by drill down on the map on this page or referral to original references as not all faults that may be significant can be mentioned. The Akatore Fault is of potential significance as it is the most active fault close to the city of Dunedin and full rupture would be associated with coastal tsunami risk. There have been two ruptures within

2419-470: The generic M w scale. See Moment magnitude scale § Subtypes for details. Seismic moment is considered the most objective measure of an earthquake's "size" in regard of total energy. However, it is based on a simple model of rupture, and on certain simplifying assumptions; it does not account for the fact that the proportion of energy radiated as seismic waves varies among earthquakes. Much of an earthquake's total energy as measured by M w  

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2478-485: The last 1300 years. It is unknown if the offshore Green Island Fault is related. If it is, the potential for significant human and property hazard from a whole fault rupture is considerably increased. The onland 23 km (14 mi) fault has at least a 5 km (3.1 mi) offshore extension to the south, and a 9 km (5.6 mi) offshore extension towards Dunedin's coastal suburbs. One recent rupture caused 7.4 m (24 ft) of slip. Before recent activity in

2537-532: The last 15,000 years it had been quiescent for over 100,000 years. The recent activity implies a slip rate of 6 mm (0.24 in)/year with recurrence average of 1700 years. The fault is named for the Akatore Creek, a small stream which flows to the Pacific south of Taieri Mouth . The Titri Fault (also known as Titri fault system or Titri fault zone ) passes through the western suburbs of Dunedin, often along

2596-400: The maximum amplitude of the ground shaking, without distinguishing the different seismic waves. They underestimate the strength: The original "Richter" scale, developed in the geological context of Southern California and Nevada, was later found to be inaccurate for earthquakes in the central and eastern parts of the continent (everywhere east of the Rocky Mountains ) because of differences in

2655-519: The measurement procedures and equations for the principal magnitude scales, M L  , M s  , mb , mB  and mb Lg  . The first scale for measuring earthquake magnitudes, developed in 1935 by Charles F. Richter and popularly known as the "Richter" scale, is actually the Local magnitude scale , label ML or M L . Richter established two features now common to all magnitude scales. All "Local" (ML) magnitudes are based on

2714-502: The mid-range approximately correlates with the original "Richter" scale. Most magnitude scales are based on measurements of only part of an earthquake's seismic wave-train, and therefore are incomplete. This results in systematic underestimation of magnitude in certain cases, a condition called saturation . Since 2005 the International Association of Seismology and Physics of the Earth's Interior (IASPEI) has standardized

2773-402: The other major faults in the area. An earthquake radiates energy in the form of different kinds of seismic waves , whose characteristics reflect the nature of both the rupture and the earth's crust the waves travel through. Determination of an earthquake's magnitude generally involves identifying specific kinds of these waves on a seismogram , and then measuring one or more characteristics of

2832-620: The remote Garm ( Tajikistan ) region of Central Asia; in revised form it is still used for local and regional quakes in many states formerly aligned with the Soviet Union (including Cuba). Based on seismic energy (K = log E S , in Joules ), difficulty in implementing it using the technology of the time led to revisions in 1958 and 1960. Adaptation to local conditions has led to various regional K scales, such as K F and K S . K values are logarithmic, similar to Richter-style magnitudes, but have

2891-417: The river in their canoes the distraught young woman attempted to jump from a rock into her lover's craft but struck the prow and was killed. Adding insult to injury her head was severed and held up angrily to her people on the shore as the flotilla passed by to the sea. There were repercussions and Tukiauau and his son were pursued and eventually killed. Maori occupation continued and Edward Shortland recorded

2950-489: The river's mouth. It has a white sand beach for swimming and several picnic areas. Moturata is a distinctive landmark which can be walked to at low-tide. Caution is advised as the tides can change quickly. Another feature is the millennium walking track that follows the Taieri River from the mouth through the lower gorge to Henley . The village is located 40 kilometres (25 mi) southwest of central Dunedin on

3009-407: The same location, but twice as deep and on a different kind of fault, was felt over a broad area, injured over 300 people, and destroyed or seriously damaged over 10,000 houses. As can be seen in the table below, this disparity of damage done is not reflected in either the moment magnitude (M w  ) nor the surface-wave magnitude (M s  ). Only when the magnitude is measured on the basis of

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3068-522: The school principal. There was a Māori occupation site at Taieri Mouth, with moa bones, indicating it was from the Moa Hunter (early) period of Māori culture. According to oral tradition in the early 18th century Tuwiriroa moved from Tititea on the Kawarau River near modern Queenstown and built a pa , Motupara, near Taieri Mouth. A rival, Tukiauau, had already built a pa, Whakaraupuka, inland on

3127-507: The seismometer off-scale (a problem with the analog instruments formerly used) and preventing measurement of the maximum wave amplitude, and weak earthquakes, whose maximum amplitude is not accurately measured. Even for distant earthquakes, measuring the duration of the shaking (as well as the amplitude) provides a better measure of the earthquake's total energy. Measurement of duration is incorporated in some modern scales, such as M wpd   and mB c  . M c scales usually measure

3186-429: The spectral distribution can result in larger, or smaller, tsunamis than expected for a nominal magnitude. The tsunami magnitude scale, M t , is based on a correlation by Katsuyuki Abe of earthquake seismic moment (M 0  ) with the amplitude of tsunami waves as measured by tidal gauges. Originally intended for estimating the magnitude of historic earthquakes where seismic data is lacking but tidal data exist,

3245-681: The standardized mB BB   scale. The mb or m b scale (lowercase "m" and "b") is similar to mB , but uses only P waves measured in the first few seconds on a specific model of short-period seismograph. It was introduced in the 1960s with the establishment of the World-Wide Standardized Seismograph Network (WWSSN); the short period improves detection of smaller events, and better discriminates between tectonic earthquakes and underground nuclear explosions. Measurement of mb  has changed several times. As originally defined by Gutenberg (1945c) m b

3304-470: The usefulness of the M e   scale, it is not generally used due to difficulties in estimating the radiated seismic energy. Two earthquakes differing greatly in the damage done In 1997 there were two large earthquakes off the coast of Chile. The magnitude of the first, in July, was estimated at M w  6.9, but was barely felt, and only in three places. In October a M w  7.1 quake in nearly

3363-538: The western suburbs of Dunedin and some have considered it a splay of the Titri Fault. If defined as a separate fault it has not been active for at least 20,000 years. It is 16 km (9.9 mi) long and has a long term slip rate of 0.05 mm (0.0020 in)/year and a reoccurrence interval of about 22,000 years. The valley of the Kaikorai Stream runs along the fault. The 55 km (34 mi) long Hyde Fault

3422-436: Was based on the maximum amplitude of waves in the first 10 seconds or more. However, the length of the period influences the magnitude obtained. Early USGS/NEIC practice was to measure mb  on the first second (just the first few P waves ), but since 1978 they measure the first twenty seconds. The modern practice is to measure short-period mb  scale at less than three seconds, while the broadband mB BB   scale

3481-448: Was developed by Gutenberg 1945c and Gutenberg & Richter 1956 to overcome the distance and magnitude limitations of the M L   scale inherent in the use of surface waves. mB  is based on the P and S waves, measured over a longer period, and does not saturate until around M 8. However, it is not sensitive to events smaller than about M 5.5. Use of mB  as originally defined has been largely abandoned, now replaced by

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