Hornblow, S.; Nicol, A.; Quigley, M.; Van Dissen, R.J. 2014 Paleoseismology of the 2010 Mw 7.1 Darfield (Canterbury) earthquake source, Greendale Fault, New Zealand. Lower Hutt, N.Z.: GNS Science. GNS Science report 2014/26 27 p.
Abstract: Rupture of the previously unknown Greendale Fault was the main source of energy release of the large September 2010 Darfield Earthquake, Canterbury, New Zealand. Rupture of the Greendale Fault was large enough to reach the ground surface and it resulted in a deformation zone up to 300 m wide that comprised both concentrated (discrete faulting) and distributed (folding) deformation. Along the central portion of the 2010 ground-surface rupture, discrete surface faulting accommodates ~30% of the total right-lateral displacement; the remainder is accommodated by distributed deformation. Our ability to characterise the width of the surface-rupture deformation zone, and the relative proportions of discrete and distributed deformation, will aid in future land-use planning decisions, and the design of rupture-resilient buildings and lifelines (e.g. pipes and cable networks) on, or across, other active faults in New Zealand and elsewhere. Shallow subsurface investigations across the Greendale Fault (e.g. trench excavations, and ground penetrating radar), in combination with age dating of these shallow sediments, reveal that the most recent rupture of the Greendale Fault prior to 2010 probably occurred sometime between 20,000 and 30,000 years ago. The knowledge of the amount of time between successive ruptures (large earthquakes) on the Greendale Fault greatly aids in the appropriate application of the Ministry for the Environment’s active fault guidelines which are aimed at mitigating the impacts of building on, or near, active faults. The Greendale Fault remained undetected prior to the Darfield earthquake because evidence of fault rupture at 20,000 to 30,000 years ago had been eroded and buried by younger Waimakariri river gravels. Similar active faults with low rates of movement compared to rates of erosion and sediment accumulation are likely to be concealed near other cities in New Zealand, and elsewhere, within young geological settings similar to Canterbury. (auth)
