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Author Topic: What caused the earthquake in Melbourne, Australia?  (Read 4765 times)

Offline Damo the Optics Monkey

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Apparantly it was felt over a large area.  Here is a USGS report. The epicentre was about 110km South east of Melbourne.

It was a 4.7, which is a lare quke for Australia - there is some minor damage in the city and the power is out over parts of the city.  My parents live near the epicenter and felt it.

Fires, doughts, windstorms, now quakes for my home state of Victoria (of which Melbourne is the capital)
« Last Edit: 06/03/2009 11:39:08 by chris »


 

Offline Damo the Optics Monkey

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What caused the earthquake in Melbourne, Australia?
« Reply #1 on: 06/03/2009 11:58:25 »
postscript: I know that this earthquake is intraplate (not from plate boundaries) -  I have been interested in the dynamics of intraplate earthquakes.
 

Offline JimBob

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What caused the earthquake in Melbourne, Australia?
« Reply #2 on: 06/03/2009 23:59:33 »
The southern part of the Australian plate is bounded by a developing mid ocean ridge (the blue line just south of the continental mass of Australia, indicated in gray and white.) This extends into the Bass Straits and probably formed the Bass Strait Basin. Early seismic studies for oil and gas revealed that the basin was most likely the result of a left lateral strike-slip faulting. However, the combination of the ridge pushing Tasmania south and the spreading of the newly forming ridge differentially pushing Tasmania to the east faster than it is moving north creates stresses producing the earthquakes in the Bass Strait areas.

Complicating all of this is the spreading ridge in the Tasman Sea, compressing the Tasman "Peninsula." This ridge can be seen more dramatically on another map available at the link below the stolen picture. The reds are pressing together.
 


Image from http://www.earthbyte.org/Research/Current/Resprojects/Platekinematics/Australia/Australian.html
 

Offline Damo the Optics Monkey

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What caused the earthquake in Melbourne, Australia?
« Reply #3 on: 07/03/2009 05:57:58 »
shearing seems to be having an effect.

I wonder if the non-active hotspot south of the west Victoria volcanics has anything to do with this.

I studied all this, but I am very rusty
 

Offline JimBob

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What caused the earthquake in Melbourne, Australia?
« Reply #4 on: 07/03/2009 21:42:03 »
The present hotspot is located approximately under King Island. It is considered inactive but earthquakes are associated with it. However, the hotspot cannot be considered in isolation. All of the geological structures and the stresses are interrelated. There is no such thing as a closed system in any area of the earth. The earth itself isn't even a closed system as there are such things as earth tides.

To say the earthquake was or was not related to the hotspot is an impossible question to address.
 

Offline Damo the Optics Monkey

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What caused the earthquake in Melbourne, Australia?
« Reply #5 on: 07/03/2009 23:50:18 »
yes, that makes sense.

Gippsland (to the east of Melbourne) usually gets small tremors, looking at the map you posted earlier I think I can see why.

It is all starting to come back to me now, thank you JimBob!
 

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What caused the earthquake in Melbourne, Australia?
« Reply #5 on: 07/03/2009 23:50:18 »

 

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