Australia: The Land Where Time Began

A biography of the Australian continent 

Earthquakes in Australia

Adelaide, the capital of South Australia, is the most earthquake prone of the Australian capital cities, with many minor shocks, most of which are only detected by sensitive instruments, though there have been several in the range of 5.0-6.5 on the Richter Scale. The 5.5 earthquake that occurred on 1 March 1954 affected dormitory suburbs of Adelaide and the Adelaide Hills (Mt Lofty Ranges). The effects on the inhabited areas were lessened because they were on areas of consolidated rock. Earthquakes of the same or lower magnitude can be more damaging in areas such as alluvial plains and valleys, as are present in areas such as those surrounding Gulf St Vincent, South Australia.

Areas where damaging earthquakes are more likely are those near active faults, the Gulfs region of South Australia, the Flinders Ranges, the Simpson Desert, the area of the Darling Fault, east of Perth, the capital of Western Australia. The crystalline zone of cratons, shield areas, are less prone to earthquakes but not completely immune. An example of such quakes is the Northern Territory town of Tennant Creek. It was struck by 3 earthquakes on the same day, 22 January 1988, of magnitude 6.3, 6.4 and 6.7, following a year of minor tremors.

Minnipa Hill, a low granite dome near the township of the same name, on the Eyre Peninsula of South Australia was hit by a minor tremor. Even though it was very small as earthquakes go it had a number of effects on the rocks of the area, fault scarps, rock bursts, dislodged blocks and slabs and A-tents were formed, more of which were formed as slabs buckled following later tremors.

Another example of an earthquake on a craton occurred at the small town of Meckering 130 km to the east of Perth, Western Australia, on the Yilgarn Craton, a crystalline region, was devastated by a 6.9 magnitude earthquake, the focus of which was about 7 km below the surface, on 14 October 1968. Meckering is in the South west Seismic Zone, a belt about 60 km wide that trends NNW-SSE, that extends from Moora-Dalwallina in the north to Katanning in the south, that has many tremors. It is a short distance to the east of the Darling Fault, that is a major tectonic feature, about 1,000 km long and a vertical displacement of at least 15 km. It forms the eastern wall of a half-graben extending to the edge of the continental shelf. Many buildings were damaged or collapsed, but in some parts the structure was rotated, a feature seen after the Adelaide earthquake of 1954. Geomorphologically, the main effect of the quake was an arc about 37 km long to the west and northwest of the town, of scarps and fissures. There were also some offsets and minor en echelon patterns, the main landforms generated forming a large arc. The scarps were mostly about 1.5 m high, though they reached up to 3.0 m, but being in soil they were quickly flattened. Fence lines were offset by up to 1.5 m.

A number of circular slumps were formed in the bed of the Mortlock River, and clastic extrusions in the bed. In alleviated areas sand and mud were ejected.

 

Sources & Further reading

Twidale, C.R. & Campbell, E.M., 2005, Australian Landforms: Understanding a Low, Flat, Arid, and Old Landscape, Rosenberg Publishing Pty Ltd 

Links

  1. List of Earthquakes in Australia
  2. Tennant Quake Memories
  3. Newcastle earthquake
  4. Newcastle earthquake images
Author: M. H. Monroe
Email:  admin@austhrutime.com
Last updated 18/05/2011 

 

 

Home
Journey Back Through Time
Geology
Biology
     Fauna
     Flora
Climate
Hydrology
Environment
Experience Australia
Aboriginal Australia
National Parks
Photo Galleries
Site Map
                                                                                           Author: M.H.Monroe  Email: admin@austhrutime.com     Sources & Further reading