Anearthquake struck approximately 28 kilometres NNW of MelbourneCBD, near the suburb of SunburyinVictoria, Australia on 28 May 2023, at 23:41 local time (AEST). The earthquake measured 4.0 on the moment magnitude scale.[1] It caused minor structural damage in parts of Melbourne and was felt as far as Tasmania and the Victoria-New South Wales border. Although the earthquake was weaker than the magnitude 5.9 Mansfield earthquake in 2021, this earthquake occurred within metropolitan Melbourne, so it was felt at a similar strength there, albeit for a lesser amount of time.[6]
This earthquake occurred near the Clarkefield Fault Scarp – a neotectonic feature with a history of earthquakes between 5.3 and 2.6 million years ago. However, it is unknown whether the earthquake began in a mapped or an unmapped fault. There are many of these historic faults in Victoria, due to its seismically active history.[10]
According to Geoscience Australia, the earthquake occurred at a very shallow depth of 2 km, while the U.S. Geological Survey placed the depth at 9.0 km.[1][2] The geological fault involved has not been identified. The earthquake was preliminarily determined to have a magnitude of 3.8, but was later upgraded to a magnitude of 4.0 after a manual review two days later.[11]
The quake generated 5 to 10 seconds of shaking which was widely felt in Melbourne.[6] More than 26,000 felt reports were submitted to Geoscience Australia.[13] Slight damages including buckled roads, cracked buildings, cracked plaster and fallen pictures were reported across the northern and western suburbs of Melbourne near the epicentre region.[14][15] It was the strongest earthquake within 40 km (25 mi) of Melbourne in more than 120 years, with the last stronger earthquake being a magnitude 4.5 quake in 1902.[16]
An earthquake advice was issued by VicEmergency which covered the entirety of Greater Melbourne and parts of Victoria.[17] The earthquake made headlines in Australian news outlets the moment it occurred, due to the rarity of an earthquake within Melbourne and the unusual intensity of a low magnitude earthquake.[18]
On 30 May 2023, a 2.6 magnitude aftershock which happened 2 minutes after the initial quake was identified by Geoscience Australia after manual analysis.[19] Another 2.3-magnitude tremor occurred in the Melbourne Suburb of Croydon, about 33 km east of Melbourne's CBD at 17:03 two days later.[20] It was felt by approximately 400 people.[21]
^David L. Huston; David C. Champion; Terrence P. Mernagh; Peter M. Downes; Phil Jones; Graham Carr; David Forster; Vladimir David (2016). "Metallogenesis and geodynamics of the Lachlan Orogen: New (and old) insights from spatial and temporal variations in lead isotopes". Ore Geology Reviews. 76: 257–267. Bibcode:2016OGRv...76..257H. doi:10.1016/j.oregeorev.2015.07.005.