No part of the Earth's surface is free from earthquakes, but some regions experience them more frequently. They are most common at tectonic plate boundaries where different plates meet. The largest events usually happen where two plates are colliding, particularly around the edge of the Pacific Plate in New Zealand, Papua New Guinea, Japan and the Americas.
Intraplate earthquakes occur in the relatively stable interior of continents away from plate boundaries. They are less common and do not follow easily recognisable patterns. This type of earthquake generally originates at shallow depths.
Although Australia is not on the edge of a plate, the continent experiences earthquakes because the Indo-Australian plate is being pushed north and is colliding with the Eurasian, Philippine and Pacific plates. This causes the build up of stress in the interior of the Indo-Australian plate which is released during earthquakes.
Adelaide has the highest earthquake hazard of any Australian capital. It has experienced more medium-sized earthquakes in the past 50 years than any capital because South Australia is being slowly squeezed sideways by about 0.1 mm/yr. Although earthquakes cannot be predicted accurately, measuring these changes and combining that information with Adelaide's earthquake history helps to develop an understanding of when the next big earthquake might happen.
Australia's largest recorded earthquake was in 1941 at Meeberrie in Western Australia with an estimated magnitude of 7.2 but it occurred in a remote, largely unpopulated area. A magnitude 6.8 earthquake at Meckering in 1968 caused extensive damage to buildings and was felt over most of southern Western Australia. Earthquakes of magnitude 4.0 or more are relatively common in Western Australia with one occurring approximately every five years in the Meckering region.