Mw 7.7 SE of Loyalty Isl. - SW Pacific

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Discussion Overview

The discussion centers on a significant Mw 7.7 earthquake that occurred southeast of the Loyalty Islands on February 10, 2021. Participants explore the seismic activity associated with this event, including aftershocks and the geological context of the earthquake in relation to tectonic plate boundaries.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant reports the details of the Mw 7.7 earthquake, including its location, depth, and aftershock activity.
  • Another participant questions the occurrence of earthquakes in the middle of tectonic plates, specifically regarding the Pacific Plate and the Ring of Fire.
  • A different participant suggests that the earthquake's location is not far from the Ring of Fire, implying a connection to tectonic activity.
  • One participant clarifies that the earthquakes are not in the middle of a plate but rather at the Pacific-Indo Australian plate boundary, noting that the boundary is complex and not a single fault line.
  • Further elaboration is provided on the geological features surrounding the boundary, including loops and connections to other regions like Papua New Guinea and Japan.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between the earthquake's location and the tectonic plate boundaries, indicating that multiple competing perspectives remain in the discussion.

Contextual Notes

Participants reference the complexity of tectonic boundaries and the occurrence of seismic events in relation to these boundaries, suggesting that the discussion may involve assumptions about plate tectonics that are not fully articulated.

davenn
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A very large Mw 7.7 quake occurred Se of the Loyalty Islands on the 10 Feb ( UT)
This location is ESE of New Caledonia and SSE of Vanuatu.

Time: 2021-02-10 13:19:55 (UTC)
Location: 23.054°S 171.601°E
Depth: 10.0 km

M 7.7 - southeast of the Loyalty Islands (usgs.gov)

It maxed out my main long period seismometer
The main shock was preceded by a number of M5+ and two M6+ events
There have been many M5+ and several M6+ aftershocks. The largest aftershock so far is an Mw6.4

Long period high gain channel, centered on 15 seconds

210210 1320UT M7.7 Loyalty Isl zhi.gif


Intermediate period channel centered on 5 seconds

210210 1320UT M7.7 Loyalty Isl zlo1.gif
Intermediate period channel centered on 5 second showing the larger aftershocks

210210 1320UT M7.7 Loyalty Isl zlo1 showing aftershocks.gif
Dave
 
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Earth sciences news on Phys.org
210210 M7.7 Loyalty Isl.JPG
 
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I thought the fire ring was the border of the pacific plate. Where do those earthquakes in the middle of the plate come from?
 
fresh_42 said:
I thought the fire ring was the border of the pacific plate. Where do those earthquakes in the middle of the plate come from?
They are on the Pacific - Indo Australian plate boundary, and definitely not in the middle of a plate :smile:

If you look around the boundary, you will find lots of loops like this one. The boundary isn't always a single fault line.

Northern end PNG to Japan via Philippines, note the big loop east of the Philippines

Philippines area.jpg


Fiji to Philippines via PNG
Vanuatu region.jpg


closer up of the Fiji to PNG region ... note the comments ...
New Caledonia region.jpg
 
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