Marlborough fault system

The Marlborough fault system consists of four main dominantly strike-slip fault strands, which together carry almost all of the displacement associated with the plate boundary. Estimates of the rate of current displacement for total strike-slip across the system are between /year to /year. Other smaller faults form as splays of these main faults or accommodate deformation of the crust between them, such as the Newton and Hura Faults at the western end of the Hope Fault and the Jordan Thrust that formed the Seaward Kaikōura Range. The dextral strike-slip across this zone has also involved clockwise rotation of the intervening fault blocks of about 20° since the early Pliocene. == Development ==

It appears from the latest studies of the rupture complexity of the 2016 Kaikōura earthquake that the myriad of faults associated with deformation episodes over the past 100 million years are important to propagation of rupture in large events in the southern part of the Marlborough fault system as due to their reorientation they act as reactivated interconnections between the current major now dominant strike-slip faults. == Faults ==

There are four main fault strands, being the Hope, Clarence, Awatere and Wairau faults, although many other smaller faults, of either strike-slip or thrust type are known. Main faults Hope Fault The Hope Fault forms the southernmost part of the Marlborough fault system. The estimated slip-rate during the Holocene is , just over half of the plate boundary displacement. At its northeastern end it links into the Jordan Thrust and most of the displacement is transferred onto that structure. It takes its name from the Hope River, which runs along one of the central fault segments. The Kekerengu Fault and Jordan Thrust are closely associated with the Hope Fault. An extra 10° of clockwise rotation has been recognised within the block that lies northeast of the tip of the Clarence fault. It takes its name from the Waiau Toa / Clarence River, which follows the fault trace in the northeastern section of the fault. Awatere Fault It is formed of two main segments; the Molesworth section to the southwest and the Eastern section to the northeast. The estimated recent slip-rate for the Molesworth section is . It takes its name from the Awatere River whose valley follows the fault trace along some of its length. Wairau Fault The Wairau Fault is sometimes regarded as a direct continuation of the Alpine Fault and may be referred to as the Alpine-Wairau Fault. It takes its name from the Wairau River, which follows the fault trace for most of its length. It has an estimated slip-rate of . Smaller Faults Kekerengu Fault 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. Before joining with the Clarence Fault, The offshore segment of the Kekerengu Fault is known as the Needles Fault. In the 7.8 () 2016 Kaikōura earthquake major rupture of both the Kekerengu Fault for , Elliott Fault branches from the central portion of the Clarence Fault and then rejoins it. The Acheron and Dillon sinsteral faults also connect these two faults. ==Seismicity==

All parts of the Marlborough fault system are currently seismically active. Historical earthquakes (since European settlement) have occurred on both the Hope and Awatere Faults and on the smaller Poulter Fault. Studies of the geomorphology and the use of trenching across fault strands, has identified many earthquakes that occurred during the Holocene on many parts of the fault system. The Hope Fault, which has the fastest slip rate is characterised by the shortest recurrence interval. The complexity of the 7.8 2016 Kaikōura earthquake completely redefined the understanding of the dynamics of the seismicity in the southern section of the fault system. As the recent movements of all the main faults is now understood, future forecasting of major earthquakes in the area may improve. ==See also==