Assessing Queensland's earthquake and tsunami risk

2018 and 2019 represent two significant anniversaries in Australia’s earthquake history. 2018 marked 100 years since the ‘Great Queensland Quake’ of 1918 with this year marking 30 years since the tragic events of the Newcastle earthquake. If these same events occurred today, they would likely still have catastrophic consequences for local communities, and State-wide economic impacts.

The Hazard and Risk Unit, Queensland Fire and Emergency Services

The magnitude 6.05 ‘Great Queensland Quake’ of 1918 occurred off Lady Elliot Island (north east of Bundaberg) on 7 June 1918, and was felt as far north as Mackay, as far west as Charleville, and as far south as Grafton in New South Wales. The magnitude of this earthquake was more intense than the 1989 Newcastle earthquake. The challenge for the emergency management sector within Queensland is enforcing the message that just because a significant earthquake hasn’t occurred in recent memory, this does not mean that it cannot happen. This is equally as true for the risk from Tsunami in Queensland where a lack of general awareness of Queensland’s exposure, and myths such as immunity to risk due to the presence of the Great Barrier Reef, persist.

The Queensland State Earthquake Risk Assessment 2019 (SERA) and companion Tsunami Guide for Queensland were developed to provide a comprehensive overview of earthquake and tsunami risk for the State. Detailed analysis of these hazards understandably requires a high level of technical expertise, as such Queensland Fire and Emergency Services partnered with Geoscience Australia to help contextualise the findings of the National Seismic Hazard Assessment 2018 and the Probabilistic Tsunami Hazard Assessment 2018. Additional expertise was also drawn from Queensland Department of Environment and Science’s Coastal Impacts Unit, and the Universities of Queensland (UQ) and Newcastle (UON) who provided the Queensland context for each hazard.

The SERA has included occurrence probabilities for several timeframes for each source zone in Queensland, for a magnitude 5.35 (1989 Newcastle event) and 6.05 (1918 Gladstone event) earthquake. This is to highlight the significant difference in occurrence probabilities between these two events, as well as highlighting the need to consider seismic activity in long-term planning decisions.

A key finding of the SERA is that the highest risk in Queensland encompasses a large area in the State’s south east, from Gladstone in the north to Logan and Scenic Rim in the south, and from the coast across to the Burnett and Western Downs regions. This considers the probability of earthquake occurrence in these areas, as well as the density of population, infrastructure, and economic activity in the area.

Both the State Earthquake Risk Assessment and Tsunami Guide for Queensland can be found at www.disaster.qld.gov.au/qermf.