Date: May 19, 2021 at 11:10:51 From: blindhog 6th sense, [DNS_Address] Subject: I Wonder What Happened 599 km Deep in the Crust Below...
... Argentina that caused the 5.1 magnitude quake on 5/19/21 15:06:54 UTC?
That's a fairly large quake.
Was it just a further movement of either the Nazco Plate moving down, or the South American plate moving up, a combination of both, or did a large section of one of either of those plates snap off?
I wonder if there are instruments which can detect the difference in sound, vibrations, or whatever it is they measure, than can tell scientists the answers to that question?
Date: May 21, 2021 at 16:07:02 From: blindhog 6th sense, [DNS_Address] Subject: Hmm, It's Interesting That a 72 Story Skyscraper is a close...
...antipode of the 5.1 earthquake, with a depth of 598km, that struck Santiago Del Esteem Prob., Argentina and started unexplainably shaking about the same time.
The skyscraper is in Shenzhen China, north-northwest of Hong Kong. And it started shaking on May 18 and again on May 20.
The deep 5.1 earthquake was on May 19.
I can't be the only one who thinks there's a relationship between these two events.
Date: May 23, 2021 at 09:24:58 From: Skywise, [DNS_Address] Subject: I made a mistake, but....
I did make a mistake. I got the latitude right, but the longitude wrong.
The quake epicenter is:
28.386°S 63.296°W
You reverse the latitude, but add/subtract 180° to the longitude.
28.386°N 116.704°E
Which places the antipode near Nanchang, China. That's about 420 miles/677 km north-northeast of Shenzhen.
Closer than my first erroneous location, but still far enough away I think to not be meaningful. Seismically, that's far enough apart that if, for example, two large quakes occurred that far apart they would not be considered related, except maybe for the largest M9 events.
One must be wary of coincidences. They DO happen. Our brains are naturally wired to look for patterns. It's a survival instinct. Hence why we see faces in clouds and rock formations.
So it's important to look at the facts and use carefully reasoned scrutiny and logic to determine the truth.
According to news reports, the shaking started on May 18th, at about 12:30pm local time. Shenzhen time zone is UTC+8, so that's 04:30 UTC.
The quake occurred on May 19th, at 15:06:54 UTC.
It's immediately obvious the quake happened 35 hours AFTER the skyscraper shaking.
Date: May 23, 2021 at 08:29:45 From: blindhog 6th sense, [DNS_Address] Subject: You'd Lose Your Bet
An antipode is found on the opposite part of the earth, which would be something in the range of 12,450 miles away from Shenzhen, China.
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Date: May 19, 2021 at 21:46:20 From: Skywise, [DNS_Address] Subject: Re: I Wonder What Happened 599 km Deep in the Crust Below...
Pieces of subducted plate don't "snap off" in the sense you may be thinking. Remember, these are processes that happen over extremely long time scales. The section of slab where this quake occurred probably took mny millions of years to be subducted that deep.
Also, it's not like the slab is floating in emptiness. It's surrounded by other rock, albeit rock of slightly different composition and conditions. So where would it "snap off" to?
Another point is that this is 'only' a magnitude 5.1 event. Quakes happen across fault surfaces, like the plane between two bricks. The size of a quake is related to the area of the fault surface that ruptured and how far it moved. Quakes of this size rupture an area of maybe a couple ten's of kilometers squared at best.
On the other hand, what IS happening is much more interesting.
These are known as deep focus earthquakes and are an active area of study. It's not well understood just what causes quakes this deep as the physics of the rock as we understand it shouldn't allow fault rupture at these depths. Quite simply, the rock should be too 'soft' to fracture in any brittle way.
For the quake in question, I used my Quake3D visualization tool to poke around the area. This quake occurred along a line of deep focus quakes in the region. Some quite large, reaching into the magnitude 7's. The placement of historical quakes quite nicely outlines the subducting Pacific plate as it dives below South America. However, the quakes along the subduction zone cease much shallower than this quake. Yet, if we extrapolate deeper along the same path, we eventually reach the depth of this quake and find a whole zone running north/south along the subduction zone. It's like the subducting slab has become too soft to fracture yet something new happens at this depth as the softened slab continues further down into the mantle.
The possibilities are discussed in the Wikipedia article on deep focus quakes. Some of the more likely explanations involve chemical or crystalline structure changes caused be the extreme pressures at these depths.
Sorry I don't have any images or video from my software. I've been very busy with work lately and just don't have the time at the moment. Working 50+ hours over 6 days a week. I really want to start making videos and posting them on YouTube. Discussing something like this quake is what I have in mind. Playing around with my software has enlightened me to some very interesting seismic structures deep within the Earth that I wasn't aware of before.
Date: May 21, 2021 at 01:02:59 From: blindhog 6th sense, [DNS_Address] Subject: OK, I'm Going to Play Devil's Advocate
In paragraph two you say there are rocks all around so there's no place for the slab to break off.
In paragraph five you say that at that depth the rocks should be soft.
So I'm saying, using a simple comparison, like the lava flows we watch in Iceland, we notice the top of the lava flow has a slight crust on top of it because it is being "hardened" by the cool air, well wouldn't the same kind of principle apply below the earth...the part of the subducting slab (which could be 50 to 100 miles in thickness) that is farthest away from the hottest deep area (kind of like the the crust on the top of the lava) would be cooler and therefore be able to "snap off to" the soft rock you described in your 5th paragraph.
Re your comment about the size of the quake, yes, it was only a 5.1, but seeing as how it was nearly 350 miles below the surface, in a way isn't it kind of like being in Reno and feeling a 5.1 quake from some quake that happened in San Francisco. I mean, whatever happened 350 miles away (or below) must have been something huge?
As an aside, while driving through Arkansas or Missouri I saw where the highway had been cut through rock which had a pattern in it of waves, as if the rock at one time was so soft and the pressure from something was so strong, that that pressure was able to squish the rock but not snap it. It obviously was rock that originally came from the deep part of the earth...meaning a humongous event happened on/in earth that would bring that rock to the surface.
Also, I hope they are paying you time and a half for those extra 10 hours per week.
Date: May 21, 2021 at 21:33:54 From: Skywise, [DNS_Address] Subject: Re: OK, I'm Going to Play Devil's Advocate
Last question first, of course I'm getting time and a half. Makes for some nice paychecks!!!
"Soft" is a relative term. The rock is still very much solid. The analogy to the lava flows in Iceland isn't quite accurate. The Earth's interior isn't liquid like that except in the outer core, which is nearly 3,000km/1,800mi deep.
The subducting slab is typically 10km/6mi thick orless.
A mag 5 quake is hardly "huge" in the grand scheme of things. Quake magnitudes are logarithmic. A single magnitude jump is approximately 32 times the energy. So a mag 9 like Japan or Sumatra releases 1 million times more energy. That *IS* huge.
Road cuts can be great places to see some great geology. What you saw in that articular one sounds like 'folding'. Layers of rock laid down as sediment, when driven deep within the Earth by tectonic force can come under tremendous pressures. Although the rock is still solid, on time scales of millions of years, it still 'flows'. Given enough time and pressure, those layers can get squished together like taffy.
Again at these depths the rock is still solid. If it were possible to visit such rock at these conditions, it would still be quite hard. You could bang it with a hammer and break chips off.
Tectonic forces involve pressures on the order of tens to hundreds of thousands of atmospheres - over a million psi. This is from the tremendous weight of the overlying rock bearing down.
And those same tectonic forces that drove those layers deep within the earth to become squished and folded under pressure can also drive them back to the surface, sometimes to be seen in road cuts. But do remember, these forces are acting over tens or hundreds of millions of years.
So again, when I said 'soft', it's in a relative way. The rock at these depths is hot enough and under enough pressure than it's soft enough to not break in a brittle fashion, like snapping a Butterfinger bar. Instead, it should be malleable more like a caramel bar.
Below is a good video I know of demonstrating how folds form.
Brian
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Date: May 19, 2021 at 17:06:38 From: Roger , [DNS_Address] Subject: Re: I Wonder What Happened 599 km Deep in the Crust Below...
Seismograph stations provide most of the information but what that information reveals is left up to human interpretation.
Check the NEIC website to see if anything is posted.