PODCAST: Canterbury earthquake a week on – what the experts know

Earthquake experts Dr Ken Gledhill and Professor Martha Savage held a public lecture in Wellington today looking at the scientific data gathered during and following last Saturday’s 7.1 magnitude earthquake in Canterbury and what it tells us.

Source: Frequency
Source: Frequency

Key talking points
– The 7.1M earthquake was a strike-slip quake – the ground, according to Professor Savage “slides past itself horizontally, with very little up or down movement. The fault ruptured east to west away from Christchurch.
– The fault was previously unknown, buried under huge amounts of gravel 90km from the Alpine faultline where largescale seismic activity was expected.
– The quake consisted of two big pulses – the second was larger but lasted for a shorter period of time.
– Extensive displacement of land in some areas eg: Highfield Road – 3.8m displacement horizontally, 1.6m vertically. This type of displacement has been identified in old faultlines in places like the Wairarapa where a fault had horizontal displacement of 120m and vertical displacement of 20m.

Extent of damage
– Incredibly lucky no one was killed, especially by falling chimneys.
– Liquefaction and falling brickwork caused most of the damage.
– Liquefaction caused significant damage to water and sewerage systems.

– Aftershocks have been “decaying” and will get smaller and less frequent over the next few months.
– There is the likelihood of “one or two more” magnitude 5 or greater quakes still to come.

Ongoing monitoring
– Temporary seismometers have been deployed to more accurately gauge the size and location of aftershocks.
– 200 seismometers from Stanford University are being deployed across the region, in some cases in people’s homes.
– GPS stations are being used to determine how much the ground has shifted (surface deformation).

Questions remaining
– How can we find other unknown faults in New Zealand?
– Can earthquakes interact and have an impact on each other? If so, how?
– What can we learn about the emotional impact of people in the wake of disasters like this? Can we better predict earthquakes?
– What can we learn to improve building standards?

Click below to listen to audio from the lecture…

Dr Ken Gledhill, Duty Seismologist at Geonet


Professor Martha Savage, School of Geography, Environment and Earth Sciences, Victoria University