Awatere Fault

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Awatere Fault
LocationSouth Island, New Zealand
CountryNew Zealand
Characteristics
Segments2; Molesworth and Eastern
Length175km
Tectonics
Plate Australian Plate, Pacific Plate
StatusActive
Earthquakes 1848 Marlborough earthquake
Type dextral strike-slip fault
New Zealand geology database (includes faults)
Map of the Marlborough Fault System MarlboroughFaultSystem.png
Map of the Marlborough Fault System

The Awatere Fault is an active dextral (right lateral) strike-slip fault in the northeastern part of South Island, New Zealand. It forms part of the Marlborough Fault System, which accommodates the transfer of displacement along the oblique convergent boundary between the Indo-Australian Plate and Pacific Plate, from the transform Alpine Fault to the Hikurangi Trough subduction zone. [1] The 1848 Marlborough earthquake was caused by rupture of the whole of the eastern section of the Awatere Fault. [2] The 175 km (109 mi) long Awatere Fault is formed of two main segments; the Molesworth section to the southwest and the Eastern section to the northeast. [3] A further strand links the southwestern end of the Eastern section to the Clarence Fault, passing through Barefell Pass. [4]

Contents

Molesworth section

The Molesworth segment of the Awatere Fault runs from close to the junction between the Alpine and Wairau Faults near Lake Tennyson, to near Molesworth Station in the northeast. It is about 55 km (34 mi) in length and consists of several smaller segments. This section has an overall strike of N7580°E, giving local zones of transtension at some of the segment boundaries, such as at Isolated Flat. [5]

Eastern section

The Eastern section of the fault runs from Molesworth Station to the coast, near White Bluffs, without significant segmentation. [4] Shallow-crust seismic studies in Cook Strait extend the fault about 20 km (12 mi) beyond White Bluffs into Cook Strait. The Awatere River, occupying the Awatere Valley, follows the trace of much of the eastern section of the fault, giving its name to the whole structure. [2] :375–376

Recent seismicity

The Molesworth section appear to have moved twice since about 3000 years ago, in events with slip values of about 6–7 m (20–23 ft). [5] Trenching at Saxton River at the eastern end of the Molesworth section suggests 8 ruptures since about 6,300 years ago, with an estimated mean recurrence of about 800 years. [6] Evidence from the eastern section of the fault suggests that there were 910 earthquakes in the period from 8610 BP to AD 1848. This gives a mean recurrence interval of 820950 years. [7] In 1848 a minimum 110 km (68 mi) length section of the fault ruptured, causing an earthquake of an estimated magnitude of about 7.5 Mw . [2] :375 It is possible that up to 140 km (87 mi) of the fault ruptured. [2] :379 The rupture appears to have bypassed the Molesworth section of the fault, continuing on the southern strand through Barefell Pass. [4]

Seismic hazard

Seismic hazard on the Eastern section is considered low, with only about 150 years since the last major earthquake on that section and an estimated recurrence interval of 6002500 years. [3]

Related Research Articles

<span class="mw-page-title-main">Alpine Fault</span> Large geological fault in New Zealand

The Alpine Fault is a geological fault that runs almost the entire length of New Zealand's South Island, being about 600 km (370 mi). long, and forms the boundary between the Pacific Plate and the Australian Plate. The Southern Alps have been uplifted on the fault over the last 12 million years in a series of earthquakes. However, most of the motion on the fault is strike-slip, with the Tasman district and West Coast moving north and Canterbury and Otago moving south. The average slip rates in the fault's central region are about 38 mm (1.5 in) a year, very fast by global standards. The last major earthquake on the Alpine Fault was in about 1717 AD with a great earthquake magnitude of Mw8.1± 0.1. The probability of another one occurring before 2068 was estimated at 75 percent in 2021.

<span class="mw-page-title-main">Hope Fault</span> Active fault in New Zealand

The Hope Fault is an active dextral strike-slip fault in the northeastern part of South Island, New Zealand. It forms part of the Marlborough Fault System, which accommodates the transfer of displacement along the oblique convergent boundary between the Indo-Australian Plate and Pacific Plate, from the transform Alpine Fault to the Hikurangi Trough subduction zone.

<span class="mw-page-title-main">San Jacinto Fault Zone</span> Southern Californian fault zone

The San Jacinto Fault Zone (SJFZ) is a major strike-slip fault zone that runs through San Bernardino, Riverside, San Diego, and Imperial Counties in Southern California. The SJFZ is a component of the larger San Andreas transform system and is considered to be the most seismically active fault zone in the area. Together they relieve the majority of the stress between the Pacific and North American tectonic plates.

The 1855 Wairarapa earthquake occurred on 23 January at about 9.17 p.m., affecting much of the Cook Strait area of New Zealand, including Marlborough in the South Island and Wellington and the Wairarapa in the North Island. In Wellington, close to the epicentre, shaking lasted for at least 50 seconds. The moment magnitude of the earthquake has been estimated as 8.2, the most powerful recorded in New Zealand since systematic European colonisation began in 1840. This earthquake was associated with the largest directly observed movement on a strike-slip fault, maximum 18 metres (59 ft). This was later revised upward to about 20 m (66 ft) slip, with a local peak of 8 m (26 ft) vertical displacement on lidar studies. It has been suggested that the surface rupture formed by this event helped influence Charles Lyell to link earthquakes with rapid movement on faults.

The 1848 Marlborough earthquake was a 7.5 earthquake that occurred at 1:40 a.m. on 16 October 1848 and whose epicentre was in the Marlborough region of the South Island of New Zealand.

The 1843 Whanganui earthquake occurred on 8 July at 16:45 local time with an estimated magnitude of 7.5 on the Mw scale. The maximum perceived intensity was IX (Violent) on the Mercalli intensity scale, and possibly reaching X (Extreme). The epicentre is estimated to have been within a zone extending 50 km northeast from Whanganui towards Taihape. GNS Science has this earthquake catalogued and places the epicentre 35 km east of Taihape, near the border of Hawke's Bay. This was the first earthquake in New Zealand over magnitude 7 for which written records exist, and the first for which deaths were recorded.

<span class="mw-page-title-main">Marlborough fault system</span> Active fault system in New Zealand

The Marlborough fault system is a set of four large dextral strike-slip faults and other related structures in the northern part of South Island, New Zealand, which transfer displacement between the mainly transform plate boundary of the Alpine fault and the mainly destructive boundary of the Kermadec Trench, and together form the boundary between the Australian and Pacific Plates.

<span class="mw-page-title-main">Wairau Fault</span> Active fault in New Zealand

The Wairau Fault is an active dextral strike-slip fault in the northeastern part of South Island, New Zealand. It forms part of the Marlborough Fault System, which accommodates the transfer of displacement along the oblique convergent boundary between the Indo-Australian Plate and Pacific Plate, from the transform Alpine Fault to the Hikurangi Trough subduction zone.

<span class="mw-page-title-main">Clarence Fault</span> Active fault in New Zealand

The Clarence Fault is an active dextral strike-slip fault in the northeastern part of South Island, New Zealand. It forms part of the Marlborough Fault System, which accommodates the transfer of displacement along the oblique convergent boundary between the Indo-Australian Plate and Pacific Plate, from the transform Alpine Fault to the Hikurangi Trough subduction zone.

<span class="mw-page-title-main">North Island Fault System</span> Fault zone of the east coast of New Zealands North Island

The North Island Fault System (NIFS) is a set of southwest–northeast trending seismically-active faults in the North Island of New Zealand that carry much of the dextral strike-slip component of the oblique convergence of the Pacific Plate with the Australian Plate. However despite at least 3 km (1.9 mi) of uplift of the axial ranges in the middle regions of the fault system during the last 10 million years most of the shortening on this part of the Hikurangi Margin is accommodated by subduction.

<span class="mw-page-title-main">Wairarapa Fault</span> Active seismic fault in New Zealand

The Wairarapa Fault is an active seismic fault in the southern part of the North Island of New Zealand. It is a dextral strike-slip fault with a component of uplift to the northwest as expressed by the Rimutaka Range. It forms part of the North Island Fault System, which accommodates the transfer of displacement along the oblique convergent boundary between the Indo-Australian Plate and Pacific Plate.

<span class="mw-page-title-main">Wellington Fault</span> Active seismic fault in New Zealand

The Wellington Fault is an active seismic fault in the southern part of the North Island of New Zealand. It is a dextral (right-lateral) strike-slip fault with variable amounts of vertical movement causing uplift to the northwest, as expressed by a series of ranges. It forms part of the North Island Fault System, which accommodates the transfer of displacement along the oblique convergent boundary between the Indo-Australian Plate and Pacific Plate.

<span class="mw-page-title-main">Kekerengu Fault</span> Active fault in New Zealand

The Kekerengu Fault is an active dextral strike-slip fault in the northeastern part of South Island, New Zealand. It is closely associated with the Hope Fault and Jordan Thrust at its south-easternmost edge and likely joins with the Clarence Fault to form the Wairarapa Fault offshore in Cook Strait.

The 1850 Xichang earthquake rocked Sichuan Province of Qing China on September 12. The earthquake which caused major damage in Xichang county had an estimated moment magnitude of 7.3–7.9 Mw  and a surface wave magnitude of 7.5–7.7 Ms . An estimated 20,650 people died.

The Taupō Fault Belt contains many almost parallel active faults, and is located in the Taupō Rift of the central North Island of New Zealand geographically between Lake Taupō and the lakes of Rotorua, Tarawera, Rotomahana and Rerewhakaaitu. The potential active fault density is very high, with only 0.1 to 1 km separating the north-east to south-west orientated normal fault strands on detailed mapping of part of the belt. The Waikato River bisects the western region of the belt.

<span class="mw-page-title-main">Wairoa North Fault</span> Active fault in New Zealand

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The Rangipo Fault is the eastern Taupō rift-bounding north–south striking normal fault complex of the Ruapehu Graben, a seismically active area of the central North Island of New Zealand to the west of Mount Ruapehu. It could be part of a Mw7.1 potential rupture.

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<span class="mw-page-title-main">Otago fault system</span> System of geological faults in the south-east of New Zealands South Island

The Otago fault system contains multiple faults with the potential to have rupture events greater than Mw7 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.

The Hundalee Fault in northern coastal Canterbury, New Zealand had a significant rupture in the 7.8 Mw 2016 Kaikōura earthquake for a minimal length of 23 km (14 mi) and as such was a key linkage fault in this complex earthquake. It is located between Parnassus in the Hurunui District and runs off shore from near Oaro.

References

  1. Langridge, R.; Campbell J.; Hill N.; Pere V.; Pope J.; Pettinga J.; Estrada B.; Berryman K. (2003). "Paleoseismology and slip rate of the Conway Segment of the Hope Fault at Greenburn Stream, South Island, New Zealand" (PDF). Annals of Geophysics. 46 (5). Retrieved 27 June 2010.
  2. 1 2 3 4 Mason, D.P.M.; Little, T.A. (2006). "Refined slip distribution and moment magnitude of the 1848 Marlborough earthquake, Awatere Fault, New Zealand". New Zealand Journal of Geology and Geophysics. 49 (3): 375–382. doi:10.1080/00288306.2006.9515174.:375
  3. 1 2 Geotech Consulting Ltd (May 2003). "Identification of active fault traces in Marlborough District". Marlborough District Seismic Hazard Investigation Programme. Archived from the original on 22 May 2010. Retrieved 2 July 2010.
  4. 1 2 3 Grapes, R.; Little T.A.; Downes G. (1998). "Rupturing of the Awatere Fault during the 1848 October 16 Marlborough earthquake, New Zealand: historical and present day evidence" (PDF). New Zealand Journal of Geology & Geophysics. 41 (4): 387–399. Bibcode:1998NZJGG..41..387G. doi:10.1080/00288306.1998.9514818 . Retrieved 2 July 2010.[ permanent dead link ]
  5. 1 2 McCalpin, J.P. (1996). "Tectonic geomorphology and Holocene paleoseismicity of the Molesworth section of the Awatere Fault, South Island, New Zealand" (PDF). New Zealand Journal of Geology and Geophysics. 39 (1): 33–50. Bibcode:1996NZJGG..39...33M. doi:10.1080/00288306.1996.9514693 . Retrieved 2 July 2010.[ permanent dead link ]
  6. Little, T. "Stop 2: Awatere Fault - south of Dashwood Pass at Calrossie Station" (PDF). Field Trip Guides, Geological Society of New Zealand 50 Annual Conference, Kaikoura, New Zealand. p. 92. Archived from the original (PDF) on 25 May 2010. Retrieved 2 July 2010.
  7. Mason, D.P.M.; Little T.A.; van Dissen R.J. (2006). "Refinements to the paleoseismic chronology of the eastern Awatere Fault from trenches near Upcot Saddle, Marlborough, New Zealand". New Zealand Journal of Geology and Geophysics. 49 (3): 383–397. Bibcode:2006NZJGG..49..383M. doi:10.1080/00288306.2006.9515175. S2CID   128479940.