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Research papers, University of Canterbury Library

Active faults capable of generating highly damaging earthquakes may not cause surface rupture (i.e., blind faults) or cause surface ruptures that evade detection due to subsequent burial or erosion by surface processes. Fault populations and earthquake frequency-­‐magnitude distributions adhere to power laws, implying that faults too small to cause surface rupture but large enough to cause localized strong ground shaking densely populate continental crust. The rupture of blind, previously undetected faults beneath Christchurch, New Zealand in a suite of earthquakes in 2010 and 2011, including the fatal 22 February 2011 moment magnitude (Mw) 6.2 Christchurch earthquake and other large aftershocks, caused a variety of environmental impacts, including major rockfall, severe liquefaction, and differential surface uplift and subsidence. All of these effects occurred where geologic evidence for penultimate effects of the same nature existed. To what extent could the geologic record have been used to infer the presence of proximal, blind and / or unidentified faults near Christchurch? In this instance, we argue that phenomena induced by high intensity shaking, such as rock fragmentation and rockfall, revealed the presence of proximal active faults in the Christchurch area prior to the recent earthquake sequence. Development of robust earthquake shaking proxy datasets should become a higher scientific priority, particularly in populated regions.

Research papers, University of Canterbury Library

The Stone Jug Fault (SJF) ruptured during the November 14th, 2016 (at 12:02 am), Mw 7.8 Kaikōura Earthquake which initiated ~40 km west-southwest of the study area, at a depth of approximately 15 km. Preliminary post-earthquake mapping indicated that the SJF connects the Conway-Charwell and Hundalee faults, which form continuous surface rupture, however, detailed study of the SJF had not been undertaken prior to this thesis due to its remote location and mountainous topography. The SJF is 19 km long, has an average strike of ~160° and generally carries approximately equal components of sinistral and reverse displacement. The primary fault trace is sigmoidal in shape with the northern and southern tips rotating in strike from NNW to NW, as the SJF approaches the Hope and Hundalee faults. It comprises several steps and bends and is associated with many (N=48) secondary faults, which are commonly near irregularities in the main fault geometry and in a distributed fault zone at the southern tip. The SJF is generally parallel to Torlesse basement bedding where it may utilise pre-existing zones of weakness. Horizontal, vertical and net displacements range up to 1.4 m, with displacement profiles along the primary trace showing two main maxima separated by a minima towards the middle and ends of the fault. Average net displacement along the primary trace is ~0.4m, with local changes in relative values of horizontal and vertical displacement at least partly controlled by fault strike. Two trenches excavated across the northern segment of the fault revealed displacement of mainly Holocene stratigraphy dated using radiocarbon (N=2) and OSL (N=4) samples. Five surface-rupturing paleoearthquakes displaying vertical displacements of <1 m occurred at: 11,000±1000, 7500±1000, 6500±1000, 3500±100 and 3 (2016 Kaikōura) years BP. These events produce an average slip rate since ~11 ka of 0.2-0.4 mm/yr and recurrence intervals of up to 5500 years with an average recurrence interval of 2750 yrs. Comparison of these results with unpublished trench data suggests that synchronous rupture of the Hundalee, Stone Jug, Conway-Charwell, and Humps faults at ~3500 yrs BP cannot be discounted and it is possible that multi-fault ruptures in north Canterbury are more common than previously thought.

Articles, UC QuakeStudies

This report describes the earthquake hazard in Waimate and Mackenzie districts and the part of Waitaki district within Canterbury, and gives details of historic earthquakes. It includes district-scale (1:500,000) active fault, ground shaking zone, liquefaction and landslide susceptibility maps. The report describes earthquake scenarios for a magnitude 7.2-7.4 Ostler Fault earthquake near Twizel, a magnitude 8 Alpine Fault earthquake, and a magnitude 6.9 Hunters Hills Fault Zone earthquake near Waimate. See Object Overview for background and usage information.

Research papers, University of Canterbury Library

A zone of active tectonism occurs in mid and north Canterbury, from the Rakaia to the Waipara Rivers, which coincides with seismicity concentrations and several Quaternary surface anomalies and is here defined as the Porters Pass Tectonic Zone. Although parallel to the Marlborough faults to the north, the lack of regional definition suggests this zone is much younger in its inception reflecting a southward movement of the plate rotation vector. The objectives of this study were to map the structures associated with this zone in the segment between the Rakaia and Waimakariri Rivers with detailed analysis concentrated in the upper Kawai Valley. Quaternary offsets on the main lineament of the Porters Pass Fault were traced through the area and evidence for the rate of movement, probable magnitudes and return periods of related seismic events was sought. The basement was found to be complicated by pre-existing deformation structures in Torlesse Group rocks which have been subsequently been re-activated or rotated by recent fault movement probably beginning in the Pleistocene. This phase is dominantly thrusting and uplift has lead to the erosion of most of the overlying sedimentary cover. Remnants of the Cret-Tertiary sediments still remain as fault-bounded packets. Evidence suggests that a change to development of a regional lateral shear associated with the Porters Pass Tectonic Zone transects the thrust system with complex interaction between the older reverse and new strike-slip faults. Offset rates along the segments of the Porters Pass Fault are not well constrained but are believed to be approximately in the range of 11-13 mm/year for at least the last 130,000 years. This rate is similar to other large faults in the Marlborough region. Two earthquake events have been identified and dated at 600 and 2000 years ago, with a magnitude of greater than 6.5. Evidence suggests characteristic earthquakes along the Porters Pass Fault are greater than Magnitude 7. This result has some major ramifications for the expected seismic hazards for nearby Christchurch.

Research papers, University of Canterbury Library

The Mw 7.8 Kaikōura earthquake ruptured ~200 km at the ground surface across the New Zealand plate boundary zone in the northern South Island. This study was conducted in an area of ~600 km2 in the epicentral region where the faults comprise two main non-coplanar sets that strike E-NE and NNE-NW with mainly steep dips (60о-80°). Analysis of the surface rupture using field and LiDAR data provides new information on the dimensions, geometries and kinematics of these faults which was not previously available from pre-earthquake active faults or bedrock structure. The more northerly striking fault set are sub-parallel to basement bedding and accommodated predominantly left-lateral reverse slip with net slips of ~1 and ~5 m for the Stone Jug and Leader faults, respectively. The E-NE striking Conway-Charwell and The Humps faults accrued right-lateral to oblique reverse with net slips of ~2 and ~3 m, respectively. The faults form a hard-linked system dominated by kinematics consistent with the ~260° trend of the relative plate motion vector and the transpressional structures recorded across the plate boundary in the NE South Island. Interaction and intersection of the main fault sets facilitated propagation of the earthquake and transfer of slip northwards across the plate boundary zone.

Images, Alexander Turnbull Library

Two huge wrestlers, one representing 'Port Hills fault' and the other 'Greendale fault' struggle together over a broken Christchurch. Another wrestler, representing 'Other faults' appears in the distance yelling 'Is it my turn yet?' Context - Christchurch has now had three major earthquakes and thousands of aftershocks. It now appears likely that the Christchurch quakes resulted from activity on a fault extending directly eastward from the Alpine fault that remained unknown until last year, says Roger Musson, a seismologist at the British Geological Survey in Edinburgh. The new fault first came to light last September (4th) when a stronger but less calamitous quake shook Darfield, 40 kilometres west of Christchurch. Musson says the latest quake (Feb 22, 2011) probably resulted from an eastward continuation of activity on the same fault. "It has probably not moved for tens of thousands of years, so lots of strain built up," says Musson. The third major quake happened on 13th June 2011. (New Scientist - February 22, 2011) Quantity: 1 digital cartoon(s).

Articles, UC QuakeStudies

This report describes the earthquake hazard in Ashburton district and gives details of historic earthquakes. It includes district-scale (1:250,000) active fault, ground shaking zone, liquefaction and landslide susceptibility maps. The report describes earthquake scenarios for a magnitude 7.0-7.3 earthquake on the Mt Hutt-Mt Peel Fault Zone and a magnitude 8 Alpine Fault earthquake. See Object Overview for background and usage information.

Articles, UC QuakeStudies

This report describes the earthquake hazard in Selwyn district and gives details of historic earthquakes. It includes district-scale (1:250,000) active fault, ground shaking zone, liquefaction and landslide susceptibility maps. The report describes earthquake scenarios for a magnitude 7.0-7.3 earthquake on the Porters Pass-Amberley Fault Zone and a magnitude 8 Alpine Fault earthquake. See Object Overview for background and usage information.

Articles, UC QuakeStudies

This report describes the earthquake hazard in Timaru district and gives details of historic earthquakes. It includes district-scale (1:250,000) active fault, ground shaking zone, liquefaction and landslide susceptibility maps. The report describes earthquake scenarios for a magnitude 7.0-7.3 earthquake on the Mt Hutt-Mt Peel Fault Zone and a magnitude 8 Alpine Fault earthquake. See Object Overview for background and usage information.