Why was there liquefaction in Christchurch?
Christchurch is very familiar with liquefaction, with parts of the city experiencing significant liquefaction as a result of the 2010/2011 Canterbury Earthquakes. Following the earthquakes, a lot of information has been collected about the city’s ground conditions.
How is liquefaction caused by earthquakes?
Earth scientist Professor Mike Sandiford, of the University of Melbourne, says liquefaction happens when a quake shakes up water sitting in loosely packed sediment about 10 to 20 metres below the ground, turning the usually solid soil into a liquid.
Where does liquefaction usually occur?
saturated soils
Liquefaction occurs in saturated soils, that is, soils in which the space between individual particles is completely filled with water. This water exerts a pressure on the soil particles that influences how tightly the particles themselves are pressed together.
What happened during the Christchurch Earthquake 2011?
The Mw6.2 (ML6.3) earthquake struck the Canterbury region in the South Island, centred 6.7 kilometres (4.2 mi) south-east of the centre of Christchurch, the country’s second-most populous city. It caused widespread damage across Christchurch, killing 185 people, in the nation’s fifth-deadliest disaster.
What damage did liquefaction cause in Christchurch 2011?
The earthquake caused 182 fatalities, collapse of two multi-storey reinforced concrete buildings, collapse or partial collapse of many unreinforced masonry structures including the historic Christchurch Cathedral.
How does liquefaction occur?
Liquefaction takes place when loosely packed, water-logged sediments at or near the ground surface lose their strength in response to strong ground shaking. Liquefaction occurring beneath buildings and other structures can cause major damage during earthquakes.
Where is liquefaction most likely to occur following an earthquake?
WHERE IT IS LIKELY TO HAPPEN. Liquefaction is most likely to happen in reclaimed land. Areas with shallow water tables and close to the sea or rivers are also susceptible to liquefaction.
Why was the Christchurch earthquake 2011 so destructive?
The increased liquefaction caused significant ground movement, undermining many foundations and destroying infrastructure, damage which “may be the greatest ever recorded anywhere in a modern city”. 80% of the water and sewerage system was severely damaged.
How is liquefaction caused?
Liquefaction occurs when the structure of a loose, saturated sand breaks down due to some rapidly applied loading. As the structure breaks down, the loosely-packed individual soil particles attempt to move into a denser configuration.
What were the environmental impacts of the Christchurch earthquake?
The Canterbury earthquakes caused a significant change to the natural environment, including liquefaction, lateral spread near waterways, land level changes, and numerous rockfalls and landslides. Air and water quality were also impacted, with water-based recreational activities halted until November 2011.
What type of areas are highly susceptible to liquefaction?
Poorly drained fine-grained soils such as sandy, silty, and gravelly soils are the most susceptible to liquefaction. Granular soils are made up of a mix of soil and pore spaces. When earthquake shock occurs in waterlogged soils, the water-filled pore spaces collapse, which decreases the overall volume of the soil.