Very Strong Quake Off Chile With Tsunami Warnings

[William Parcher]

Chile earthquake: 8.3-magnitude quake strikes off coast

A powerful 8.3-magnitude earthquake struck off Chile's coast on Wednesday, according to a preliminary assessment from the U.S. Geological Survey. The quake's epicenter was about 55 kilometers (34 miles) west of Illapel, Chile, USGS said. It occurred around 7:54 p.m. (6:45 p.m. ET) and had a depth of 33 kilometers (20.5 miles).

Chile's national emergency agency issued a tsunami warning, ordering evacuations in coastal areas from Arica to Puerto Aysen. There were reports of damages to homes in Illapel, Interior Minister Jorge Burgos told reporters.

"Widespread hazardous tsunami waves are possible" along the coast of Chile and Peru, the Pacific Tsunami Warning Center said, and a tsunami watch is in effect for Hawaii. A strong aftershock could be felt in the country's capital, CNN sister network CNN Chile reported...

 

[cullennz]

That is a very very big quake

 

[William Parcher]

The depth given is obviously wrong. Other reports are saying 4.8 miles.

 

[Dinwar]

Preliminary reports are pretty bad when it comes to earthquakes. Self-reporting is a big issue in the USA--it takes a while to sort through the idiotic nonsense ("It was a 9.0!!!!!" when the windows barely rattle, that sort of thing), and triangulating the depth can take time. Doesn't help that earthquakes happen in areas that are crossed by fault zones.

Seems a bit large for that depth and the setting. A deeper quake would be more likely, as part of a subducting slab snaps off. Shallower quakes are more likely, given the faults and the volcanism, but they'd be less powerful I would think, because less force is required to move the shallower rocks around. It's certainly not impossible, just weird.

 

[William Parcher]

Dinwar, the USGS first said 7.9 then immediately updated it to 8.3.

There were numerous aftershocks with 3 of them at magnitude 6.

Any tsunami waves will reach Hawaii at about 3am. The whole Pacific is standing by for updates.

 

[Dinwar]

Dinwar, the USGS first said 7.9 then immediately updated it to 8.3.

What was the methodology? They use several, of varying accuracy--as evidenced by the adjustment you mentioned.

 

[William Parcher]

USGS General Summary.

The September 16, 2015 M8.3 earthquake west of Illapel, Chile, occurred as the result of thrust faulting on the interface between the Nazca and South America plates in Central Chile. At the latitude of this event, the Nazca plate is moving towards the east-northeast at a velocity of 74 mm/yr with respect to South America, and begins its subduction beneath the continent at the Peru-Chile Trench, 85 km to the west of the September 16 earthquake. The size, location, depth and mechanism of this event are all consistent with its occurrence on the megathrust interface in this region...

 

[cullennz]

Equivalence - 8.35

50 megatons 210 PJ
Tsar Bomba—Largest thermonuclear weapon ever tested. Most of the energy was dissipated in the atmosphere.
The seismic shock was estimated at 5.0–5.2[23]

 

[William Parcher]

Pacific Tsunami Warning Center with watch/warning messages and updates.

 

[Dinwar]

Okay, so it was related to the plates themselves, not the volcanism. Got that part right, at least! Still surprised at the shallow depth, though.

 

[William Parcher]

Okay, so it was related to the plates themselves, not the volcanism. Got that part right, at least! Still surprised at the shallow depth, though.

But isn't it generally true that where plates meet you have volcanism?

 

[Dinwar]

But isn't it generally true that where plates meet you have volcanism?

Not necessarily. See the San Andreas, or a few other faults in California. It's also not true that you need plates meeting to have volcanism--see caulderas.

The issue is, which is the primary driver HERE? Was the earthquake caused by shifts in magma chambers/shallow faults, or was it caused more directly by the subducting plate? In this case, it seems clear that the subducted plate caused the quake, meaning it's not volcanism.

 

[William Parcher]

Reports of large tsunami waves on Chilean coastline.

 

[William Parcher]

PTWC measuring 10.2 foot waves near epicenter at coastline. The tsunami is on.

 

[cullennz]

PTWC measuring 10.2 foot waves near epicenter at coastline. The tsunami is on.

Surfing down, surfing down, surfing around.....................ouch!!!

Hope they got the warnings

 

[William Parcher]

Coastal cities reporting flooding.

 

[William Parcher]

Dinwar, Chile is on The Ring of Fire. Plates meeting and volcanism.

 

[Dinwar]

Dinwar, Chile is on The Ring of Fire. Plates meeting and volcanism.

That was my point. The two cause quakes in very different ways, which produce very different quakes. It can have both. The shallow depth indicated one, the magnitude indicated the other, which meant that there was some ambiguity in the cause from my perspective.

If it was in California, Ohio, or Washington there wouldn't be a question really.

 

[Skeptic Ginger]

Lot of ongoing updates here:
http://www.theguardian.com/world/li...o-live-updates#block-55fa156ee4b0d1b4cd9dd42e

 

[William Parcher]

All eyes on French Polynesia (Tahiti) as being next in the tsunami path.