Nev, the Newcastle earthquake was a lot more severe than quite a mild tremor. It was a magnitude 5.6 event. Meckering in WA was 6.5 and Australia's strongest ever recorded earthquake was 6.6 at Tennant Creek. Granted that on a log scale, 5.6 represents a lot less energy than 6.6, but Newcastle was a significant event and Australia's most costly in terms of property damage. It killed 13 people, hospitalised 160 and damaged over 35,000 homes, 147 schools and 3000 commercial buildings and cost about $4b. It also led to the Earthquake Design Code being substantially overhauled to make buildings more resilient.
Unlike other types of loads such as wind (including cyclones), and live load where the aim is to prevent any significant damage in a worst case event, the aim in earthquake design is to prevent loss of life, not to prevent damage to the structure. The aim is to have the structure fail in a predicable way but hold together long enough to allow people to get out. The structure may well be uninhabitable after the event and need to be demolished.