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

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Discussion Overview

The discussion centers around two significant seismic events: a Mw 7.4 earthquake south of Tonga and a Mw 8.3 earthquake off the southwest coast of the Kamchatka Peninsula. Participants explore the characteristics of these earthquakes, including their depths, wave patterns, and geological implications, with a focus on the technical aspects of seismic monitoring and analysis.

Discussion Character

  • Technical explanation
  • Exploratory

Main Points Raised

  • One participant notes that the Mw 7.4 quake occurred at a depth of 171 km within the Tonga-Kermadec Trench, highlighting the relationship between subduction rates and earthquake depth.
  • Another participant mentions that the Mw 8.3 quake was recorded at a depth of 608 km, emphasizing the absence of surface waves due to its depth and the predominance of body waves in the seismic data.
  • There is a discussion about the complexity of the subduction process, where the outer edges of the subducting slab warm faster than the core, allowing for continued fracturing and seismic activity at great depths.
  • Participants share links to seismic data visualizations, indicating ongoing monitoring of both events.

Areas of Agreement / Disagreement

Participants generally agree on the technical details regarding the depths and characteristics of the earthquakes, but there is no explicit consensus on the broader implications of these events or their geological significance.

Contextual Notes

The discussion does not resolve the complexities of the subduction process or the implications of the observed seismic activity, leaving open questions about the geological dynamics at play.

davenn
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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
 
Earth sciences news on Phys.org
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 existent 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
 
I have attached the image here, for the latecomers.

attachment.php?attachmentid=58983&stc=1&d=1369382846.gif


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

Keep these reports coming!
 

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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
 
No problem, just tell me what "Reg." means? Registered?
 
Reg = region :)
 
Oops, OK.
 

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