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Images, eqnz.chch.2010

One Month after the Christchurch Earthquake. The mangled remains of the pedestrian bridge over the river Avon Twitter | Facebook | My ...

Images, eqnz.chch.2010

One Month after the Christchurch Earthquake. The mangled remains of the pedestrian bridge over the river Avon Twitter | Facebook | My ...

Research papers, University of Canterbury Library

The Avon and Heathcote Rivers, located in the city of Christchurch, New Zealand, are lowland spring-fed rivers linked with the Christchurch Groundwater System. At present, the flow paths and recharge sources to the Christchurch Groundwater System are not fully understood. Study of both the Avon and Heathcote Rivers can provide greater insight into this system. In addition, during the period 2010-2012, Christchurch has experienced large amounts of seismic activity, including a devastating Mw 6.2 aftershock on February 22nd, 2011, which caused widespread damage and loss of life. Associated with these earthquakes was the release of large amounts of water through liquefaction and temporary springs throughout the city. This provided a unique opportunity to study groundwater surface water interactions following a large scale seismic event. Presented herein is the first major geochemical study on the Avon and Heathcote Rivers and the hydrological impact of the February 22, 2011 Christchurch Earthquake. The Avon, Heathcote, and Waimakariri Rivers were sampled in quarterly periods starting in July 2011 and analyzed for stable Isotopes δ¹⁸O, δD, and δ¹³C and major anion composition. In addition, post -earthquake samples were collected over the days immediately following the February 22, 2011 earthquake and analyzed for stable isotopes δ¹⁸O and δD and major anion composition. A variety of analytical methods were used identify the source of the waters in the Avon-Heathcote System and evaluate the effectiveness of stable isotopes as geochemical tracers in the Christchurch Groundwater System. The results of this thesis found that the waters from the Avon and Heathcote Rivers are geochemically the same, originating from groundwater, and exhibit a strong tidal influence within 5km of the Avon-Heathcote Estuary. The surface waters released following the February 22nd, 2011 earthquake were indistinguishable from quarterly samples taken from the Avon and Heathcote Rivers when comparing stable isotopic composition. The anion data suggests the waters released following the February 22nd, 2011 Christchurch Earthquake were sourced primarily from shallow groundwater, and also suggests a presence of urban sewage at some sites. Attempts to estimate recharge sources for the Avon-Heathcote Rivers using published models for the Christchurch Groundwater System yielded results that were not consistent between models. In evaluating the use of geochemical constituents as tracers in the Christchurch Groundwater System, no one isotope could provide a clear resolution, but when used in conjunction, δ¹⁸O, δ¹³C, and DIC, seem to be the most effective tracers. Sample sizes for δ¹³C were too small for a robust evaluation. Variability on the Waimakariri River appears to be greater than previously estimated, which could have significant impacts on geochemical models for the Christchurch Groundwater System. This research demonstrates the value of using multiple geochemical constituents to enrich our understanding of the groundwater surfaces-water interactions and the Christchurch Groundwater System as a whole.

Images, UC QuakeStudies

A digitally manipulated photograph of the badly twisted Medway Street footbridge. The photographer comments, "This bridge over the Avon River in Christchurch, New Zealand has been left in place since the first major earthquake back in September 2010. Graffiti artists or taggers are still leaving their marks on it even though it is nearly twisted at 90 degrees at one point".

Images, UC QuakeStudies

The badly twisted Medway Street footbridge. The photographer comments, "The September 4th 2010 earthquake in Christchurch was so violent that the banks of the Avon River moved towards each other. This footbridge being metal had to twist sideways to release the pressure of being pushed from both river banks. It looked like it had been wrung out like a wet towel".

Images, UC QuakeStudies

A photograph of the street number and apartment numbers at 440 Oxford Terrace spray-painted on the footpath in front. The street number is written as 466 but this is the incorrect number for this site. The photographer comments, "The numbers were spray-painted in front of all the properties in the Avon Loop in order to keep track of the property number after the mailboxes were lost or removed".

Videos, UC QuakeStudies

A video telling the story of a Dallington house which was built by Bill Cooper in 1957. The house was demolished last month as part of the clearance of the Christchurch residential red zone. The story of the house is used to illustrate what is happening in many Christchurch suburbs. The video also includes the story of a sea elephant that lived in the Avon River in the 1970s and 1980s.

Images, UC QuakeStudies

A two-storey house in Avonside Drive with a warped upper balcony. The photographer comments, "This house is on Avonside Drive opposite the Avon River. The land in this area spread laterally and had bad liquefaction of the soil. This caused some houses to sink into the ground, but as the balcony supports did not sink as much the balcony came to rest at a crazy angle".