Hope Fault
Encyclopedia
The Hope 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 Trench
subduction zone
.
, with an offshore continuation of at least 13 km. It consists of several segments, from the southwest end, the Kelly Fault, then the Hurunui, Hope River, Conway and Seaward segments. It takes its name from the Hope River, which follows the trace of much of the Hope River segment.
, the Kelly Fault marks a sharp reduction in velocities to the northwest of the Kelly and Hura faults.
data, extending for at least another 13 km.
formed at the overlap between the Hope River and Conway segments of the Hope Fault. The right-stepping geometry of the offset between the two segments has caused local extension to occur and a basin to form. The hot spring
s of Hanmer Springs
are one of the results of the basin formation. Other smaller basins of similar type have formed at minor offsets along the Hope River segment. The basin began to form in the Pleistocene
and contains more than 1000 m of sedimentary fill in the main depocenter. The eastern end of the basin is currently being deformed by transpression
associated with the southwestern end of the Conway segment. The destruction of the basin at its eastern end is matched by transtensional deformation at the western end that continues to enlarge the basin, giving rise to a roughly steady-state geometry. The basin fill is being constantly reworked as it is uplifted at the basin's eastern end and redeposited to the west.
, which ruptured the whole of the Hope River segment. Alexander McKay, a geologist working for the New Zealand geological survey, observed horizontal offsets in farm fences of between 1.5 and 2.6 metres along the fault. He was the first to associate a strike-slip displacement with an earthquake. The longest segment, the Conway segment, shows evidence of past earthquakes, although none have been recorded since European settlement in about 1850. investigations show that at least 3 events have occurred, the most recent of which is dated as between 1720-1840 A.D.
Active fault
An active fault is a fault that is likely to have another earthquake sometime in the future. Faults are commonly considered to be active if there has been movement observed or evidence of seismic activity during the last 10,000 years....
dextral (right lateral) strike-slip fault in the northeastern part of South Island
South Island
The South Island is the larger of the two major islands of New Zealand, the other being the more populous North Island. It is bordered to the north by Cook Strait, to the west by the Tasman Sea, to the south and east by the Pacific Ocean...
, New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
. It forms part of the Marlborough Fault System
Marlborough Fault System
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...
, which accommodates the transfer of displacement along the oblique convergent boundary between the Indo-Australian Plate
Indo-Australian Plate
The Indo-Australian Plate is a major tectonic plate that includes the continent of Australia and surrounding ocean, and extends northwest to include the Indian subcontinent and adjacent waters...
and Pacific Plate
Pacific Plate
The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At 103 million square kilometres, it is the largest tectonic plate....
, from the transform Alpine Fault
Alpine Fault
The Alpine Fault is a geological fault, more specifically known as a right-lateral strike-slip fault, that runs almost the entire length of New Zealand's South Island. It forms a transform boundary between the Pacific Plate and the Indo-Australian Plate. Earthquakes along the fault, and the...
to the Hikurangi Trench
Hikurangi Trench
The Hikurangi Trench is a linear deep in the Pacific Ocean off the east coast of the North Island of New Zealand, lying between the southern end of the Cook Strait and the Chatham Rise. Though much shallower, it is the southward continuation of the Kermadec Trench and forms part of the...
subduction zone
Subduction
In geology, subduction is the process that takes place at convergent boundaries by which one tectonic plate moves under another tectonic plate, sinking into the Earth's mantle, as the plates converge. These 3D regions of mantle downwellings are known as "Subduction Zones"...
.
Extent
The Hope Fault branches off from the Alpine Fault south of Hokitika and then runs in a nearly straight line for about 230 km to the east coast of South Island just north of KaikouraKaikoura
Kaikoura is a town on the east coast of the South Island of New Zealand. It is located on State Highway 1 180 km north of Christchurch.Kaikoura became the first local authority to reach the Green Globe tourism certification standard....
, with an offshore continuation of at least 13 km. It consists of several segments, from the southwest end, the Kelly Fault, then the Hurunui, Hope River, Conway and Seaward segments. It takes its name from the Hope River, which follows the trace of much of the Hope River segment.
Kelly Fault segment
The junction between the Hope fault and the Alpine Fault is complex. The Kelly Fault forms a major splay of the Hope Fault from just west of Harper Pass; it splays again to the west into the Newton and Hura faults. From repeat GPS surveying on the region near Arthur's PassArthur's Pass
Arthur's Pass is a mountain pass in the Southern Alps of the South Island of New Zealand. It marks part of the boundary between the West Coast and Canterbury regions, 140 km from Christchurch and 95 km from Greymouth. The pass lies in a saddle between the valleys of the Otira River, a...
, the Kelly Fault marks a sharp reduction in velocities to the northwest of the Kelly and Hura faults.
Hurunui segment
This 42 km long segment runs from Harper pass to the junction of the Hope and Boyle rivers. The maximum slip-rate estimated from the offset of a stream is about 13 mm/yr. A minimum slip-rate has also been estimated from offset of channels in a late Holocene alluvial fan complex of 8.1-11.0 mm/yr. The average recurrence interval for earthquake slip events on this segment is 310–490 yr.Hope River segment
The Hope River segment runs about 30 km from the confluence of the Boyle and Hope rivers as far as the Hanmer Basin. From the offset of dated river terraces, a late Holocene horizontal slip-rate of about 10 mm/yr and a vertical slip-rate of about 0.6 mm/yr have been calculated for this segment. The displacement is thought to have occurred by repeated slips which, if similar to that which caused the 1888 earthquake, indicate a repeat interval of about 140 years.Conway segment
The Conway segment is the longest and straightest of the segments with a strike of about N73°E. It extends 70 km from the eastern part of the Hanmer Basin to just west of the junction with the Jordan Thrust near Kowhai River. The slip-rate for this segment, estimated from offset alluvial features, is about 23 mm/yr. The fault dips steeply to the northwest at about 70° and forms the southern termination of the Seaward Kaikoura, Hawk and Amuri ranges. This topography is a result of the significant component of reverse displacement on this fault zone. An average recurrence interval of 180–310 yr has been calculated for earthquakes along this segment.Seaward segment
The Seward segment extends from near Kowhai River to the coast and has been recognised on the continental shelf from seismic reflectionReflection seismology
Reflection seismology is a method of exploration geophysics that uses the principles of seismology to estimate the properties of the Earth's subsurface from reflected seismic waves. The method requires a controlled seismic source of energy, such as dynamite/Tovex, a specialized air gun or a...
data, extending for at least another 13 km.
Hanmer Basin
Hanmer Basin is a small (10 x 20 km) pull apart basinPull Apart Basin
250px|thumb|[[Cami Lake]] in [[Tierra del Fuego]] develops on a [[Patagonian Ice Sheet|glacially]] excavated pull apart basin along the [[Magallanes-Fagnano Fault]], hence its elongated form...
formed at the overlap between the Hope River and Conway segments of the Hope Fault. The right-stepping geometry of the offset between the two segments has caused local extension to occur and a basin to form. The hot spring
Hot spring
A hot spring is a spring that is produced by the emergence of geothermally heated groundwater from the Earth's crust. There are geothermal hot springs in many locations all over the crust of the earth.-Definitions:...
s of Hanmer Springs
Hanmer Springs
Hanmer Springs is a small town in the Canterbury region of the South Island of New Zealand. It is located 65 kilometres southwest of Kaikoura , in the Hurunui District. The town lies on a minor road 9 kilometres north of State Highway 7, the northern route between Christchurch and the West Coast...
are one of the results of the basin formation. Other smaller basins of similar type have formed at minor offsets along the Hope River segment. The basin began to form in the Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....
and contains more than 1000 m of sedimentary fill in the main depocenter. The eastern end of the basin is currently being deformed by transpression
Transpression
Transpression is a geological term used to describe a region of the Earth's crust that experiences strike-slip shear and a component of shortening, resulting in oblique shear. Transpression typically occurs at a regional scale, such as plate boundaries that have an oblique convergence. More...
associated with the southwestern end of the Conway segment. The destruction of the basin at its eastern end is matched by transtensional deformation at the western end that continues to enlarge the basin, giving rise to a roughly steady-state geometry. The basin fill is being constantly reworked as it is uplifted at the basin's eastern end and redeposited to the west.
History
The oldest fill in the Hanmer Basin is Pleistocene in age, which constrains the development of the Hope Fault to that period.Recent seismic activity
The most recent earthquake on the Hope Fault was the 1888 North Canterbury earthquake1888 North Canterbury earthquake
The 1888 North Canterbury earthquake is the name associated with a severe earthquake which occurred at 4.10 a.m on 1 September 1888 following a sequence of foreshocks that started the previous evening, and whose epicentre was in the North Canterbury region of the South Island of New Zealand.In...
, which ruptured the whole of the Hope River segment. Alexander McKay, a geologist working for the New Zealand geological survey, observed horizontal offsets in farm fences of between 1.5 and 2.6 metres along the fault. He was the first to associate a strike-slip displacement with an earthquake. The longest segment, the Conway segment, shows evidence of past earthquakes, although none have been recorded since European settlement in about 1850. investigations show that at least 3 events have occurred, the most recent of which is dated as between 1720-1840 A.D.
Seismic hazard
All segments of the Hope Fault are likely to experience future earthquakes, the largest such events, a possible magnitude 7.5, would be expected from the Conway segment or the Jordan Thrust.External links
- Picture of the Hope Fault at Te Ara - The Encyclopedia of New Zealand
