What's Causing All These Earthquakes Today?

[davenn]

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)

 

[davenn]

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

 

[fresh_42]

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?

 

[davenn]

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 ...

annotated map

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