Future Risk

Adelaide is considered to be the most likely city in Australia at risk of experiencing a significant earthquake.According to Judith Carr, Earthquake Hazard Leader for SA, “there has been significant residential and commercial development over the last 50 or so years and so a greater impact than occurred in 1954 would be expected” and that, “We have scenarios of damage likely for various earthquake magnitudes and, for exercise purposes only, assume that damage from an earthquake event would be similar to that of the 1989 Newcastle earthquake”. This Newcastle earthquake is the worst in Australian history as it killed 13 people, and had an approximate damage amount of $1.5 billion.

With this information in mind, it is understandable why South Australia became the first state in Australia in 1983 to adopt national standards to make buildings earthquake resistant. Therefore buildings that were created after 1983 are believed to be able to withstand an earthquake as their materials are designed to be flexible rather than rigid, allowing them to absorb the energy of a tremor more efficiently.

Surprisingly, however, Adelaide is regarded as geologically stable. This is due to Adelaide being in the middle of a tectonic plate, rather than on a tectonic boundary. South Australia’s fault line are due to faults in the rock, which create earthquakes that measure low in magnitudes; usually ranging from between 1 and 4.

However, it is important to keep in mind that the prediction of earthquakes is quite ambiguous; scientists are currently working on potential methods to accurately predict an earthquake, some involving the measurement of radon gas releases from granite, others investigating electromagnetic fields, or monitoring land slippages with GPS equipment.

To determine a potential hazard of a specific area, it’s soil and rock composition must be looked at; if an area is made of unstable ground, such as sand or clay, it is more likely to experience a higher intensity of effects than an area composed of firm ground such as granite. This is because in an event of an earthquake, the vibrations move quicker through solid dense mass and slower through loose sediments, thus increasing the damage as well as the duration of an earthquake. The Para Fault Line is composed of heavy clay, sand clay, gravel, calcrete, estuarine deposits, silt stone quartz and dolomite. Therefore if an earthquake were to occur along the Para Fault Line, it’s predicted that it’s amplification of vibrations would be low to medium.

Overall, as there is no correlation between previous earthquakes in Adelaide and the fault lines present, it is difficult to determine the probability of a future earthquake occurring on the Para Fault Line, although the chances of a tremor happening would more likely be in the hills rather than the plains. With regards to shock absorbing buildings, and soil/rock composition, Adelaide is quite protected in the event of an earthquake being amplified. Places that have a higher chance to experience earthquakes are at risk if they are located on compositions prone to slope instability and liquefaction, rather than closer proximity to a fault.  Scientists believe that Australia experiences an earthquake with a magnitude of 6 once every 5-6 years, and it has been a while since a last major earthquake has happened, therefore it is not a question of ‘if’ but rather when another will occur.

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