Mw 7.4 Quake S of Tonga and Mw 8.3 Kamchatka Reg.


by davenn
Tags: kamchatka, quake, tonga
davenn
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#1
May23-13, 11:15 PM
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A Mw 7.4 Quake S of Tonga occurred at 17:19 UT, 23-5-2013

still visible on my seismo for ~ another 24 Hrs till it scrolls off
http://www.sydneystormcity.com/sydln.gif

it was quite a deep event at 171km and within the boundary area of the down going Pacific seafloor slab along the Tonga - Kermadec Trench

Its depth meant that it didnt have high amplitude surface waves
P arrival at my station ( Sydney) @ ~ 17:25 UT and the S wave arrival just before 17:30

This trench is well known for very deep events that occur from under the North Island of New Zealand and right up via Tonga to Fiji. Events up 600+ km are not uncommon.
One of the main reasons for the quakes at great depth in this region is because of the high subduction rate along this plate boundary of up to 8cm / year. This allows the Pacific Plate to subduct to great depth before it heats and softens too much to allow fracturing to occur.

Its quite a complex process where the outer edges of the subducting slab are warming faster than its core and allowing the core to continue to fracture causing quakes long after the outer edges are softly deforming.

Dave
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davenn
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#2
May24-13, 02:45 AM
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I get home from work just a short time ago and another big quake is just tailing off.

2013/05/24 0544UT - Mw 8.3 offshore SW coast of Kamchatka Peninsula ( eastern Russia), NW Pacific.
This was one of those VERY DEEP events I spoke about in my last post. It listed at 608 km.
Again because of the depth surface waves are non existant and its primarily all the body waves that can be seen. If this had been a shallow event, less than 50km, the trace on the screen would have been covering almost top to bottom.

both events can been seen on my seismo -- http://www.sydneystormcity.com/sydln.gif

Dave
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#3
May24-13, 03:08 AM
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I have attached the image here, for the latecomers.



A little bit too wide for PF layout, but interesting enough so that I don't care.

Keep these reports coming!
Attached Thumbnails
sydln.gif  

davenn
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May24-13, 03:26 AM
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Mw 7.4 Quake S of Tonga and Mw 8.3 Kamchatka Reg.


Hi Borek
cheers

are you able to edit the thread subject line to have it read ....

Mw 7.4 Quake S of Tonga and Mw 8.3 Kamchatka Reg.

thanks lots :)

Dave
Borek
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#5
May24-13, 03:39 AM
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No problem, just tell me what "Reg." means? Registered?
davenn
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#6
May24-13, 05:40 AM
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Reg = region :)
Borek
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#7
May24-13, 05:42 AM
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Oops, OK.


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