A magnitude 2.8 earthquake woke Barossa Valley residents in South Australia early on Monday. Geoscience Australia recorded it at 2:26am, centred at Stone Well on the edge of Tanunda, about 55 kilometres north-east of Adelaide. The agency received nearly 250 felt reports.

Seismologist Tania Page told 891 ABC Adelaide a quake of this size would typically mean "maybe two or three seconds of shaking." Most reports came from Tanunda and Nuriootpa. People spoke of rattling shelves and a lot of noise. At this size, she said, it tends to sound like thunder, a passing truck or a small explosion.

Mark, in Nuriootpa, called it "pretty powerful," very bass-like. At first he thought it was thunder. It woke him at once, and the cat at the end of the bed. He reckoned three seconds, maybe more. That is a witness, not a measurement.

Geoscience Australia says quakes below 3.5 "seldom cause damage." ABC did not report significant damage. Glam Adelaide gathered accounts from Greenock, Lyndoch, Kapunda, Daveyston and Eudunda: windows, beds, a rumble. A 2.8 close to houses, at night, is louder than the number looks.

Magnitude measures energy at the source, not what a bedroom feels. Depth, distance and soil change the shake. Page did not flag a particular aftershock. A small event near a wine town can wake people without being a disaster.

The Barossa is a vineyard valley, not a belt known for destructive quakes. Shelf reports are not an inspection. Until Geoscience updates the file, the tally stays: 2.8, 2:26am, Stone Well, noise, no confirmed damage.

For residents it was thunder from the floor. For the agency it sat below the usual damage threshold. Both can be true: it was felt, it did not bring houses down.

Image: DXR, Barossa Valley from Mengler Hill, 2023, CC BY-SA 4.0, Wikimedia Commons; the vineyard, not the 2:26am shake.

Sources consulted: Magnitude-2.8 earthquake reported near Tanunda, Geoscience Australia says - ABC News; Barossa Valley rocked by early morning earthquake near Tanunda - Glam Adelaide.