What's Causing All These Earthquakes Today?

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Discussion Overview

The discussion revolves around the recent occurrences of significant earthquakes, particularly focusing on their locations and underlying geological processes. Participants explore the causes of these earthquakes, especially in relation to tectonic plate movements and fault lines, with a specific emphasis on the Mid-Atlantic Ridge.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant reports multiple recent earthquakes, including a Mw5.9 in northern Indonesia, a Mw6.3 aftershock in Chile, and a Mw6.5 in Vanuatu.
  • Another participant notes a Mw6.6 earthquake occurring at the central Mid-Atlantic Ridge, mentioning its distance from previous seismic events.
  • Questions are raised about the causes of earthquakes at the Mid-Atlantic Ridge, with one participant suggesting that tectonic plates are drifting apart.
  • A response affirms that the plates are indeed spreading apart and highlights the presence of large transform faults along oceanic spreading ridges, indicating a complex geological environment.
  • Maps are referenced to illustrate the relationship between spreading zones and transform faults, suggesting that the Mid-Atlantic Ridge is more complex than merely a spreading ridge.

Areas of Agreement / Disagreement

Participants express differing views on the complexity of the geological processes at the Mid-Atlantic Ridge, with some emphasizing the presence of transform faults while others focus on the spreading nature of the plates. The discussion remains unresolved regarding the full implications of these geological features on earthquake activity.

Contextual Notes

There are limitations in the discussion regarding the assumptions made about the geological processes, and the complexity of the fault systems is not fully explored. The relationship between the reported earthquakes and their geological context is still under examination.

davenn
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http://www.sydneystormcity.com/seismograms.htm

MY seismo has been busy over the last 4 hours

Mw5.9 northern Indonesia

Mw6.3 Chilean aftershock

And coming in now a Mw6.5 Vanuatu ( SW Pacific)
 
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davenn said:
and another large event coming in...

Mw 6.6, central Mid-Atlantic Ridge, NE of Brazil

https://earthquake.usgs.gov/earthquakes/eventpage/us7000biu8/executiveIt will be relatively small amplitude on my seismo as it's half way around the world
This event is ~ 600km NW of a Mw6.5 on the 30th Aug 2020
What causes earthquakes there? Aren't the plates drifting apart?
 
fresh_42 said:
What causes earthquakes there? Aren't the plates drifting apart?
Yes, they are spreading apart. There are lots of very large transform ( strike-slip) faults along all oceanic spreading ridges
and that's where these quakes usually occur as did this one ...

a couple of maps I have done, one annotated with which parts are spreading and which parts are transform faults

clean map showing quake location ...

Clipboard01.jpg


annotated map

Clipboard01a.JPG
Many people probably think that the Mid-Atlantic Ridge ( and others like it) are just spreading ridges.
This couldn't be further from the truth as it can be seen that it is a complex mix of spreading and fault zones
I have 1/2 arrows that indicate the relative motions on some of the faults ( didn't do all - for clarity)

cheers
Dave
 
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