An active fault is a fault that is likely to become the source of another earthquake sometime in the future. Geologists commonly consider faults to be active if there has been movement observed or evidence of seismic activity during the last 10,000 years.
16-613: The Wairau 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 . Depending on
32-470: A valley where Pleistocene and Holocene deposits have been laid down over bedrock during the last two million years and where the river often obscures recent fault traces. The underlying bedrock which is very rarely exposed along the fault line itself is to the fault's north the Dun Mountain, Maitai and Caples terranest and Triassic and Cretaceous greywacke otherwise. The western fault zone width
48-612: Is a state highway located in the northern parts of the South Island of New Zealand. It is 117 km long and runs between the settlements of Renwick (in Marlborough region ) and Kawatiri Junction (in the Tasman region) via Saint Arnaud , providing a bypass of the city of Nelson . Despite being a convenient link between the West Coast and Marlborough , and being a relatively straight highway along most of its length, it
64-470: Is about 300 m (980 ft) and contains several fault scarps up to 5 m (16 ft) high. As said above, some have regarded it as a segment of the Alpine Fault. This does not concord with the rest of the Alpine Fault having a fairly predictable relatively short recurrence interval for major earthquakes of 291 ± 21 years with good evidence for multi-segment rupture on many of these events over
80-563: Is employed with other factors to determine the potential earthquake hazard. The geologic conditions and plate tectonic setting in much of the Western U.S. has resulted in the region being underlain by relatively thin crust and having high heat flow, both of which can favor relatively high deformation rates and active faulting. In contrast, in the Central and Eastern U.S. (CEUS) the crust is thicker, colder, older, and more stable. Furthermore,
96-605: Is only classified by the NZTA as a secondary collector highway. SH 63 begins just to the east of Renwick at SH 6 , and parallels the course of the Wairau River for 93 kilometres, initially to the south of the river before crossing to the north side about 20 km from the Marlborough/Tasman border, while passing through the settlements of Wairau Valley , Hillersden and Tophouse . Just before reaching Tophouse,
112-576: The CEUS is thousands of miles from active plate boundaries, so the rates of deformation are low in this region. Nevertheless, the CEUS has had some rather large earthquakes in historical times, including a series of major earthquakes near New Madrid, Missouri in 1811–1812 , a large earthquake near Charleston, South Carolina in 1886, and the Cape Ann earthquake northeast of Boston in 1755. State Highway 63 (New Zealand) State Highway 63 (SH 63)
128-450: The area of any given plate. The fact that intraplate regions may also present seismic hazards has only recently been recognized. Various geologic methods are used to define the boundaries of an active fault such as remote sensing and magnetic measurements, as well as other ways. Several types of data, such as seismologic reports or records over time, are used to gauge fault activity. Activity and fault area are correlated, and risk analysis
144-464: The east. To the west, the fault is a single strand but near Wairau Valley township, the fault splits into two strands. These two strands continue to within about 15 kilometres (9.3 mi) of the coast near Renwick . Further to the east only the southernmost strand can be detected intermittently by lidar and with offshore mapping. It takes its name from the Wairau River , which follows the fault trace for most of its length on land. The fault follows
160-611: The fault has been more active in the last 6000 years. The recurrence interval of slip events estimated for the fault combined with the estimated time since the last event suggest "that the Wairau Fault is nearing the end of its interseismic period". The current estimated seismic hazard from the Wairau Fault is considered to be relatively high with a current slip rate of up to 3.5 mm (0.14 in)/year to accommodate. The magnitude of such an earthquake could be up to 7.7 M W . The fault runs alongside State Highway 63 to its end at
176-468: The fault that is poorly constrained in time but is between 970 and 1750 BP , and was about 6 M W . From the offset of dated river terraces a displacement of 23 m (75 ft) has been estimated along the Wairau Fault since about 5610 years BP . Trenching studies along the trace of the Wairau Fault have identified four dateable slip events within this interval, the age of latest event now on redating and further trench work at two other locations falls in
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#1732772240526192-476: The last 2000 years. The last rupture that may also have involved the Alpine Fault is about 2000 years ago which does not apply to the other active segments of the Alpine Fault (see timeline). It has been stated that " Co-rupture of the Wairau and Alpine faults during great earthquakes occurs rarely (if at all) on millennial or longer timescales. " There was an event confined to the coastal and off shore portions of
208-572: The precise definition used, the Wairau Fault runs either from southern or northern end of 'The Bends' region. In the former case it is regarded as the Wairau segment of the Alpine Fault which means the Alpine Fault is about 800 km (500 mi) long. In the latter case it is regarded as a separate fault and runs about 200 km (120 mi) from near Lake Rotoiti to the edge of the continental shelf in Cook Strait near Cloudy Bay in
224-449: The range 1930 to 2110 BP and was about 7.4 M W . The average recurrence interval for surface disrupting earthquakes along the land portion of the fault is about 1000 years. The estimated average slip for each land event is about 6 m (20 ft) and the maximum is 10 m (33 ft). However it is noted that the offshore fault record extends back 18,000 years and this has a longer recurrence interval of 2200 years, possibly because
240-530: The surface and which have evidence of movement during the Quaternary Period. Related geological disciplines for active-fault studies include geomorphology , seismology , reflection seismology , plate tectonics , geodetics and remote sensing , risk analysis , and others. Active faults tend to occur in the vicinity of tectonic plate boundaries, and active fault research has focused on these regions. Active faults tend to occur less within
256-615: The township of Renwick and presumably with full rupture would be disruptive to the town of Blenheim which is within 5 km (3.1 mi) of the fault and the port facilities of Picton less than 20 km (12 mi) away. Active fault Active faulting is considered to be a geologic hazard – one related to earthquakes as a cause. Effects of movement on an active fault include strong ground motion , surface faulting, tectonic deformation , landslides and rockfalls , liquefaction , tsunamis , and seiches . Quaternary faults are those active faults that have been recognized at
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