An earthquake occurred without warning at 10:27 am on 28 December 1989 (local time) causing loss of life in the city of Newcastle, New South Wales, Australia, the first earthquake to cause fatalities in Australia since European settlement. The magnitude is estimated to have been 5.6 on the Richter scale. Earthquakes of this size occur on average about once every eighteen months in Australia. A single aftershock was recorded on a network of ten seismographs installed on 29 December in and around Newcastle; it had a magnitude of 2.1. The focal depth of the mainshock was 11.5±0.5 km and of the aftershock 13.5±0.8 km, which is beneath the Permian sediments of the Sydney Basin. The epicentres of both earthquakes are coincident within the error bounds and are some 15 km from the centre of damage in the City. The damage in Newcastle was made worse by an underlying thin layer of alluvium which magnified the ground motion substantially. A fault-plane solution indicates that the earthquake had a thrust mechanism with nodal planes striking in a NW-SE direction, parallel to the mapped surface faults in the region. Limited strong motion data were recorded, but not close to the epicentre.