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Dr Hamish Campbell of GNS Science talks about the Christchurch earthquake and it's subsequent aftershocks.
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A team of earthquake geologists, seismologists and engineering seismologists from GNS Science, NIWA, University of Canterbury, and Victoria University of Wellington have collectively produced an update of the 2002 national probabilistic seismic hazard (PSH) model for New Zealand. The new model incorporates over 200 new onshore and offshore fault sources, and utilises newly developed New Zealand-based scaling relationships and methods for the parameterisation of the fault and subduction interface sources. The background seismicity model has also been updated to include new seismicity data, a new seismicity regionalisation, and improved methodology for calculation of the seismicity parameters. Background seismicity models allow for the occurrence of earthquakes away from the known fault sources, and are typically modelled as a grid of earthquake sources with rate parameters assigned from the historical seismicity catalogue. The Greendale Fault, which ruptured during the M7.1, 4 September 2010 Darfield earthquake, was unknown prior to the earthquake. However, the earthquake was to some extent accounted for in the PSH model. The maximum magnitude assumed in the background seismicity model for the area of the earthquake is 7.2 (larger than the Darfield event), but the location and geometry of the fault are not represented. Deaggregations of the PSH model for Christchurch at return periods of 500 years and above show that M7-7.5 fault and background source-derived earthquakes at distances less than 40 km are important contributors to the hazard. Therefore, earthquakes similar to the Darfield event feature prominently in the PSH model, even though the Greendale Fault was not an explicit model input.
On 4 September 2010, a magnitude Mw 7.1 earthquake struck the Canterbury region on the South Island of New Zealand. The epicentre of the earthquake was located in the Darfield area about 40 km west of the city of Christchurch. Extensive damage occurred to unreinforced masonry buildings throughout the region during the mainshock and subsequent large aftershocks. Particularly extensive damage was inflicted to lifelines and residential houses due to widespread liquefaction and lateral spreading in areas close to major streams, rivers and wetlands throughout Christchurch and Kaiapoi. Despite the severe damage to infrastructure and residential houses, fortunately, no deaths occurred and only two injuries were reported in this earthquake. From an engineering viewpoint, one may argue that the most significant aspects of the 2010 Darfield Earthquake were geotechnical in nature, with liquefaction and lateral spreading being the principal culprits for the inflicted damage. Following the earthquake, a geotechnical reconnaissance was conducted over a period of six days (10–15 September 2010) by a team of geotechnical/earthquake engineers and geologists from New Zealand and USA (GEER team: Geo-engineering Extreme Event Reconnaissance). JGS (Japanese Geotechnical Society) members from Japan also participated in the reconnaissance team from 13 to 15 September 2010. The NZ, GEER and JGS members worked as one team and shared resources, information and logistics in order to conduct thorough and most efficient reconnaissance covering a large area over a very limited time period. This report summarises the key evidence and findings from the reconnaissance.
Photograph captioned by Fairfax, "Nick Wright (9) explores a huge crack in the earth in Charles Street, Kaiapoi".
Photograph captioned by Fairfax, " Nick Wright (9) explores a huge crack in the earth in Charles Street, Kaiapoi".
Photograph captioned by Fairfax, "Memory Javagnwe's baby, Hayley, was born on September 4 2010 when the earth moved for all Cantabrians".
Photograph captioned by Fairfax, "Memory Javagnwe's baby, Hayley, was born on September 4 2010 when the earth moved for all Cantabrians".
Photograph captioned by Fairfax, "Memory Javagnwe's baby, Hayley, was born on September 4 2010 when the earth moved for all Cantabrians".
Photograph captioned by Fairfax, "Memory Javagnwe's baby, Hayley, was born on September 4 2010 when the earth moved for all Cantabrians".
Photograph captioned by Fairfax, "Memory Javagnwe's baby, Hayley, was born on September 4 2010 when the earth moved for all Cantabrians".
Photograph captioned by Fairfax, "Memory Javagnwe's baby, Hayley, was born on September 4 2010 when the earth moved for all Cantabrians".
Photograph captioned by Fairfax, "Ground features. Sue Irvine's Halswell property was flooded by sand volcanoes and included bubbled-up areas of earth".
Photograph captioned by Fairfax, "Volcano holes. Small volcano-shaped mounds indicate the force of water being pushed out by the earth's movement".
Photograph captioned by Fairfax, "Natalie Thomas' Birchfield Ave home looks unaffected by the earthquake but uneven floors, doors and cracks in the surrounding earth tell another tale".
Photograph captioned by Fairfax, "Locksley Avenue houses in Dallington. Owen Moore, aged 90, and dog Min laugh in the face of this afternoon's aftershock. His house was built on compacted earth alongside the Avon River".
Photograph captioned by Fairfax, "Locksley Avenue houses in Dallington. Owen Moore, aged 90, and dog Min laugh in the face of this afternoon's aftershock. His house was built on compacted earth alongside the Avon River".
On 4 September 2010, a magnitude Mw 7.1 earthquake struck the Canterbury region on the South Island of New Zealand. The epicentre of the earthquake was located in the Darfield area about 40 km west of the city of Christchurch. Extensive damage was inflicted to lifelines and residential houses due to widespread liquefaction and lateral spreading in areas close to major streams, rivers and wetlands throughout Christchurch and Kaiapoi. Unreinforced masonry buildings also suffered extensive damage throughout the region. Despite the severe damage to infrastructure and residential houses, fortunately, no deaths occurred and only two injuries were reported in this earthquake. From an engineering viewpoint, one may argue that the most significant aspects of the 2010 Darfield Earthquake were geotechnical in nature, with liquefaction and lateral spreading being the principal culprits for the inflicted damage. Following the earthquake, an intensive geotechnical reconnaissance was conducted to capture evidence and perishable data from this event. This paper summarizes the observations and preliminary findings from this early reconnaissance work.
A Simple shot down the street where the shops are now marked for demolition. Twitter | Facebook | My Website |
One Month after the Christchurch Earthquake. A view in Sydenham suburb - Columbo St Twitter | Facebook | My Website |
A corner shop in Sydenham - a Suburb of Christchurch. Front walls are all missing Twitter | Facebook | My Website |
Among the deformation features produced in Christchurch by the September 4th Darfield Earthquake were numerous and widespread “sand volcanoes”. Most of these structures occurred in urban settings and “erupted” through a hardened surface of concrete or tarseal, or soil. Sand volcanoes were also widespread in the Avon‐ Heathcote Estuary and offered an excellent opportunity to readily examine shallow subsurface profiles and as such the potential appearance of such structures in the rock record.
One Month after the Christchurch Earthquake. The mangled remains of the pedestrian bridge over the river Avon Twitter | Facebook | My ...