Landslides in the Sydney Basin - Geoscience Australia

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Seismic Hazard in SydneyProceedings of the one day workshopa magnitude estimate of about ML 4.6. It was felt with Modified Mercalli intensity 5 at Kurrajong,on the Nepean River about 50 km north-west of Sydney. Highest intensities were reported fromnorth and west of Kurrajong. The intensity in Sydney was about MM 3. It was felt by a few peopleat rest indoors in Newcastle. It was crudely located using intensity data near the north end of theLapstone Fault, and may have been on either that fault or a related fault.1961 May 21, Robertson, ML 5.5: An earthquake of magnitude ML 5.5 occurred near Robertson on1961 May 22 at 0740 am AEST. This is about 60 kilometres south-west of Sydney. It has also beencalled the Bowral earthquake. The maximum intensities in the Robertson-Bowral area were aboutMM 7. The earthquake caused significant damage to buildings in the Moss Vale, Robertson andBowral area, blocked the Macquarie Pass road with rockfalls, and caused some power failures. Theintensity in Sydney was about MM 3. The epicentre was within a few kilometres of the presentlocation of Wingecarribee Dam which was completed in 1974.1973 March 9, Burragorang, ML 5.5: An earthquake of magnitude ML 5.5 occurred near thesouthern end of Lake Burragorang, about 30 km west of Picton on 1973 March 10 at 0509 am,AEST. This is about 70 kilometres WSW of Sydney. It has also been called the Picton earthquake. Itcaused about $A500,000 (1973 values) damage. It has been suggested that the earthquake couldhave been reservoir induced, but it is difficult to prove this (Drake, 1974). If this was the case, it isan example of delayed reservoir induced seismicity. The earthquake was probably at a depthexceeding 12 km, and occurred about 12 years after reservoir filling commenced.1981 November 15, Appin, ML 4.6: An earthquake of magnitude ML 4.6 occurred near Appin on1981 November 16 at 0358 am, AEST. This is about 50 kilometres south-west of Sydney. Intensitiesof MM 4 were felt over a broad area south-west of Sydney, but with only isolated values of MM 5 inthe epicentral area. No damage was reported.1985 February 13, Lithgow, ML 4.3: An earthquake of magnitude ML 4.3 occurred near Lithgow on1985 February 13 at 0701 pm AEDT (daylight saving time). This is about 100 kilometres west ofSydney. Intensities of up to MM 7 were reported in the epicentral area, with minor damage toplaster, brickwork, tiles and chimneys, including several partly demolished chimneys. Objects felloff shelves in many parts of Lithgow. Total damage was estimated at A$65,000 (1985). Theintensity in Sydney was very low, with only a few people reporting MM 2 to 3. The earthquake wasfelt much further to the west than to the east, suggesting that it may have been on a west-dippingfault.1989 December 28, Newcastle, ML 5.6: The earthquake on Thursday 1989 December 28 at 1027 amAEDT was the first Australian earthquake confirmed to have caused fatalities. Thirteen people werekilled by the earthquake, and there were hundreds of injuries. Extensive minor and moderate damagegave a total cost that exceeded A$1,500 million. This earthquake was centred off the north-east ofthe map in figure 1, and was felt over a radius of about 300 kilometres.1999 March 17, Appin, ML 4.4: An earthquake of magnitude 4.4 occurred near Appin onWednesday 1999 March 17 at 12:58 pm AEDT. The maximum reported intensity was of MM 5,although there were some reports of minor damage in the epicentral area. It caused some powerfailures, and was felt throughout the Sydney area.49
Seismic Hazard in SydneyProceedings of the one day workshopPre- and Post-1992 SeismicityThe quality of seismograph coverage of any area changes with time, and the general trend is forimprovement with time. In the Sydney area, all events before 1960 were very poorly located usingintensity data alone.Figure 1: Sydney region earthquakes to 1992.From 1960 to 1991, there were only three to five seismographs in the area. Only smaller earthquakeswithin about 10 to 20 kilometres of these could be located with a well-defined depth estimate. The50
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