M7.7 Jamaica Quake: Surface Waves Coming Soon

[davenn]

TL;DR

Jamaica quake

Mw 7.7 quake coming in on my seismograph now

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

The surface waves have not arrived yet ( at time of writing this) they will probably max out the display

 

[phinds]

Gads, that's big. How close to the island is the epicenter, or is it ON the island?

 

[davenn]

Gads, that's big. How close to the island is the epicenter, or is it ON the island?

from the USGS map ...

 

[berkeman]

No reports of deaths or serious injuries yet (fingers crossed), but it looks like it even shook up folks in Miami for the Superbowl...

https://weather.com/news/news/2020-01-28-strong-earthquake-strikes-jamaica-cuba

 

[fresh_42]

Summary:: Jamaica quake

The surface waves have not arrived yet ...

Yeah, there is always some delay of time on Jamaica ...

 

[fresh_42]

Can't be too serious - hopefully. CNN international still covers the current farce in DC, German news channels have breaking news a) new Corona infections b) Jamaica 7.7 no damages reported so far, and another one has only the usual irrelevant news in the ticker. And @berkeman's link speaks of a possible 3ft (1m) tsunami.

 

[Astronuc]

https://earthquake.usgs.gov/earthquakes/eventpage/us60007idc/executive
Fairly shallow at 10 km.

• Lucea, Hanover, Jamaica125.9 km (78.2 mi) SSE, Population: 6289
• Montego Bay, St. James, Jamaica139.1 km (86.5 mi) SE, Population: 82867
• Niquero, Granma, Cuba140.3 km (87.1 mi) ENE, Population: 18771

I wonder how it relates to the Mag 6.4 earthquake in Puerto Rico. Seems to be same fault system.
https://earthquake.usgs.gov/earthquakes/eventpage/us70006vll/executive
https://www.usgs.gov/news/magnitude-64-earthquake-puerto-rico

 

[davenn]

I wonder how it relates to the Mag 6.4 earthquake in Puerto Rico. Seems to be same fault system.

Same plate boundary, yes. But there's over 1000km between the 2 events, so kinda like asking if a quake
near Mexico City is related to a quake in Los Angeles.
The Puerto Rico was south of the plate boundary, by some 200km, but the Jamaican event was on the boundary.

The Jamaican event was primarily strike-slip, with a little oblique slip component
The Puerto Rican event was a back arc extensional motion (normal faulting)

so both events had a very different tectonic setting

Dave

 

[anorlunda]

back arc extensional motion

Interesting. Please explain what that means. Or maybe a graphic.

 

[davenn]

Interesting. Please explain what that means. Or maybe a graphic.

OK ... A belt of extensional tectonics is a very common feature behind (back from) a subduction
trench. Because of the extensional ( pulling apart) action the crust thins creating a basin and volcanism
is the common result, eg the Taupo Volcanic Zone (TVZ) in the North Island of New Zealand and many
other places around the world. The back arc basin can be on land or in the ocean depending on how
mature the island arc is.

in the caldera, you can see the faults that angle inwards from either side. These are the extensional
(normal) faults.

((I had another couple of images to upload, but the forum is on a go-slow again for me and refuses to
upload files I will do so when it starts working properly again)))https://en.wikipedia.org/wiki/Back-arc_basin

 

[davenn]

A single normal fault

now multiple versions of the above to form a basin with a thinned crust

Dave