They range in strength from slight tremors to great shocks lasting from a few seconds to as long as five minutes. They could come in a series over a period of several days. This Scale is open-ended, as there is no upper limit to the amount of energy an earthquake might release. The most severe earthquakes so far, have not exceeded 9.5 on this Scale. This in turn is 30 times greater than a 5.0 and so on.
Some examples appear below.
Most earthquake casualties result from falling objects or debris because shocks may damage or demolish buildings and other structures. Because of Australia's geological position, we are prone to what seismologists call 'intra-plate' earthquakes. The historical record in Australia goes back only about 210 years. The first reported earthquake lasted about three seconds at Port Jackson, NSW in June, 1788. In 1837, early settlers in South Australia experienced an earthquake for 20 seconds.