Normal faults are common; they bound many of the mountain ranges of the world and many of the rift valleys found along spreading margins… This page was last edited on 6 December 2020, at 19:25. A Central Otago geologist's draft manuscript suggests a new east coast offshore tectonic fault system could be comparable in size to the Alpine Fault. Prehistoric dates of the most recent Alpine fault earthquakes, New Zealand. These had previously been determined to have occurred in approximately 1100, 1430, 1620 and 1717 CE, at intervals between 100 and 350 years. This displacement was inferred by Wellman due in part to the similarity of rocks in Southland and Nelson on either side of the Alpine Fault. In addition, an earlier earthquake was identified to have occurred between 887 and 965.[14]. Alpine Fault Tours, Whataroa Picture: Gaunt Creek exposure site - Check out Tripadvisor members' 349 candid photos and videos. Alpine Fault The Alpine fault marks the plate boundary between the [16] A 2018 study says that a significant rupture in the Alpine Fault could lead to roads (particularly in or to the West Coast) being blocked for months, as with the 2016 Kaikoura earthquake, with problems in supplying towns and evacuating tourists. Register Warranty. However, most of the motion on the fault is strike-slip (side to side), with the Tasman district and West Coast moving North and Canterbury and Otago moving South. It is the responsibility of the user of any material to obtain clearance from the copyright holder. The Australian plate is sliding horizontally towards the north-east, at the same time as the Pacific plate is pushing up, forming the … The last rupture of the Hope Fault was in 1888 when an earthquake with an estimated mome7.3 nt magnitude of 7- produced fault slip of about 2.5 m in the horizontal direction (Figure 4). [1] The Southern Alps have been uplifted on the fault over the last 12 million years in a series of earthquakes. Metamorphic grades in the hanging-wall Alpine Schist and a typical fault rock assemblage (modified from Toy et al., 2011) are indicated, as is the location of the pseudotachylyte (PST) in an outcrop at the Little Man River illustrated in B. Read more. [2], The fault zone is exposed at numerous locations along the West Coast and typically comprises a 10-50 m wide fault gouge zone with pervasive hydrothermal alteration. The dominant movement on the fault is horizontal as shown by circle symbols at the base of the figure (arrow away/towards). This study analyzes 195 earthquakes recorded during the 6 month duration of the Southern Alps Passive Seismic Experiment (SAPSE) in 1995/1996 and two M L 5.0 earthquakes and aftershocks in 1997, which occurred close to the central part of the Alpine fault. [5] Then uplift slowly began as the plate motion became slightly oblique to the strike of the Alpine Fault. The Southern Alps had not yet formed and most of New Zealand was covered in water. B: Arrows and enlargements highlight PST veins in quartzofeldspathic mylonite (photomicrograph in plane polarized light). The hanging wall slides down relative to the footwall. In the north, the fault trends offshore and into thrust type, "where tsunami can be born". In this case the mapped fault trace (rupture surface; bold red line) is located near the base of the scarp. Because of this during the mid 20th century it was speculated that the Alpine Fault creeps without making large earthquakes. Generally the fault has a simple straight trace, striking ca. Wells, A.; Yetton, M.T. 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 Alpine fault is the Pacific‐Australian plate boundary in the South Island of New Zealand. Where were New Zealand’s largest earthquakes? Paragenetic diagram showing the distribution of mineral phases in the different Alpine Fault rock types. Alpine Fault movement. Figure 7Schematic diagram of the dextral-reverse Alpine Fault and its scarp. In between is a sideways tear, the Alpine Fault. Convergence on the plate boundary along the Alpine Fault ranges from a vector trending 084° at a rate of 45 mm yr-1 (Norris et. Strike-slip faults have walls that move sideways, not up or down. This includes mylonites and the Alpine Schist, which increases in metamorphic grade towards the fault. The fault system extends northeast from the Alpine Fault near St Arnaud, through the eastern part of Tasman District and into Nelson City and Tasman Bay (Fig. This gave a mean recurrence rate of 291 years, plus or minus 23 years, down from the previously estimated rate of 329 years, plus or minus 26 years. Richard H. Sibson from the same university also used the Alpine Fault to refine his nomenclature of fault rocks which gained international adherence. The average slip rates in the fault's central region are about 38mm a year, very fast by global standards. [26][27] It was a $2.5 million international research project designed to drill 1.3 km to the fault plan in two months. The Alpine Fault then runs the length of the South Island just west of the Southern Alps to near Lewis Pass in the central northern section of the island. Other articles where Normal fault is discussed: fault: Normal dip-slip faults are produced by vertical compression as Earth’s crust lengthens. Spot the fault. Search. Between 25 and 12 million years ago the movement on the proto-Alpine Fault was exclusively strike-slip. Snow on the mountains of the Pacific plate contrasts with the lower land of the Australian plate. 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