Friday 20 April 2012

Canberra shaken by mild Earthquake.

On Friday 20 April at 5.09 am, local time (7.09 pm on Thursday 19 April GMT), the Australian capitol city, Canberra, was shaken by an Earthquake recorded by Geoscience Australia as measuring 3.7 on the Richter Scale and occurring 40 km west of the city at a depth of 4 km. There are no reports of any damage or casualties, but the quake was apparently felt across much of the city, as well as in the communities of Tumut, Murrumbateman, Batlow, Carwoola and Tuggeranong.

Map showing the location of the quake, and the area across which it was felt. Geoscience Australia.

While Canberra is a long way from any active tectonic plate margins, it is moderately Earthquake-prone. This is due to ancient folding of the rocks of the region, which has left many areas where the layers of strata are arranged vertically rather than horizontally, which is a less stable configuration. Typically strata lie flat, like a stack of books or magazines laid flat on a table. When geological movements turn these on their sides the resemble books or magazines lined up on a shelf, but without the shelf to provide a steady base. Such rocks are often prone to mild quakes.

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