An “earthquake swarm” has recently impacted the Hunter region of New South Wales, Australia, where over 30 seismic events have been documented, as reported by Geoscience Australia. Among these events, a 4.5 magnitude earthquake was recorded southwest of Muswellbrook, following a previous 4.8 magnitude quake centered near Denman.
Concurrently, another cluster of earthquakes, with magnitudes reaching up to 4.4, has been detected near Wyalkatchem in Western Australia, approximately 190 kilometers east of Perth.
Earthquake swarms, according to Adam Pascale, chief scientist at the Seismology Research Centre in Victoria, are not unusual occurrences. He describes a swarm as a temporary surge of seismic activity where significant quakes can happen at any moment.
This pattern differs from a typical earthquake scenario, which usually sees tremors diminish after the main shock. Swarms represent a natural process through which the Earth relieves accumulated tectonic stress over time, and they can manifest anywhere globally.
While swarms can occur naturally, human activities might also play a role in inducing seismic events. Pascale highlights instances in the United States where injecting wastewater back into oil wells has triggered such activities.
Earthquake Swarm Shakes New South Wales and Western Australia, Raising Concerns Over Seismic RisksSimilarly, Gary Gibson, a senior seismologist at the University of Melbourne, notes that mining activities can contribute to seismic occurrences, particularly depending on the local geology and the characteristics of faults in the area. He emphasizes that significant excavation can indeed lead to earthquakes.
Addressing the resilience of infrastructure against earthquake swarms, Gibson points out that Australia’s long periods without significant seismic activity can foster complacency regarding earthquake preparedness. The engineering standards for earthquake resistance vary widely across the globe.
For example, Chile is recognized for its advanced engineering techniques designed to enhance building safety against seismic events. Gibson also warns that the risks may be greater in Australia due to the strong, hard rocks and faults, which require a high level of stress to fail.
Predicting the conclusion of an earthquake swarm is challenging, as Gibson notes that there can be clusters of activity followed by lulls or minor shocks that may indicate a larger quake is imminent. Pascale adds that the duration of swarms can vary significantly, lasting from a few days to several months before subsiding.
This unpredictability makes it more difficult to forecast activity within a swarm compared to the more structured mainshock-aftershock sequence typically associated with individual earthquakes.