Reducing earthquake impact


Two storey building with front facade missing

Damage to a building
suffered during the 1989
Newcastle 5.6 magnitude
earthquake. Image
reproduced with
permission from
Australian Emergency

Seismologists will be better able to determine the risk of damage to buildings and infrastructure from future earthquakes in the Sydney Basin following a recent survey of seismic shear-wave velocities in the region.

Shear-waves are a form of seismic waves in which the particle motion is perpendicular to the direction in which the seismic waves are travelling. Shear-waves are particularly damaging to buildings and infrastructure.

The seismologist leading the project, Clive Collins, said that shear-wave velocity profiles to a depth of about 100 metres can help scientists estimate the amount of ground shaking which occurs under buildings and other infrastructure during an earthquake.

"Local site conditions, such as the thickness and stiffness of the underlying sediments, are important factors to investigate because the degree of ground shaking can be amplified by deep, soft sediments such as sand which can result in greater damage to buildings," Mr Collins said.

"In the recent survey, a total of 25 sites in the Sydney and Newcastle metropolitan areas were selected based on previous investigations and observations of building damage following the 1989 Newcastle 5.6 magnitude earthquake," he said.

"Four of the sites investigated are at permanent seismograph stations of the Australian National Seismic Network operated by Geoscience Australia and the results at these sites will be used to more accurately estimate the magnitudes of earthquakes," Mr Collins said.

Several seismic acquisition methods were used to collect data at each of the 25 sites. The results from these different methods will be compared, along with those from previous studies in the region, to help develop acquisition programs in other areas of Australia.

The resulting information will be used to improve models of seismic hazard and risk, which will help to reduce the effects of earthquakes on buildings and other infrastructure.