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Vito

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PostSubject: Tectonic unrest   Fri Feb 08, 2013 2:53 pm

I'm on the USGS email notification list for significant earthquakes. I've been getting an unusually high number of notifications about quakes in the vicinity of Santa Cruz Island in the South Pacific, roughly 270 miles east southeast of the Solomon Islands, and about 1,300 miles east of Port Moresby, Papua, New Guinea.

There have been 187 temblors of magnitude 4.4 or greater since January 22, with 17 of those being magnitude 6.0 or greater since January 30. The most powerful one (8.0) occurred two days ago, and caused a tsunami that reportedly killed five people and destroyed some villages.

It's not unusual to see seismic activity anywhere along the Ring of Fire, especially in the huge boundary between the Australian and the Pacific tectonic plates. But this has been an especially active cluster of seismic events, and they've been gradually increasing in magnitude over the past three weeks.

It might be a good idea to delay that vacation on Santa Cruz Island until things settle down.

jocolor
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Kyle Weiss

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PostSubject: Re: Tectonic unrest   Fri Feb 08, 2013 2:56 pm

Swarms happen. We had a bunch of them in the Reno area a few years ago, something like 30 1.5 - 3.5 mag. quakes every day for two months. Then boom, nothing.

The R.O.F. has been very quiet lately until recently. I check in at USGS quite a bit, too.

Head to Santa Cruz, just get a place to stay that has a few hundred feet of elevation. And bring a surf board.
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Vito

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PostSubject: Re: Tectonic unrest   Fri Feb 08, 2013 3:23 pm

Yeah, we get shakers here in SoCal fairly regularly, and they always happen in swarms. That's because the breaks in the fault line are seldom clean. Rocks stick to each other pretty well when they're under pressure. So they break in one place, then another, then another...IOW, swarmage of quakage.

A quake results from the difference between the coefficients of static and kinetic friction. It's the same principle as sliding a heavy object across the floor. It takes more force to get it moving (static friction) than it does to keep it moving once it gets going (kinetic friction). The same thing happens underground. The surfaces along the fault zone build up tension, but when it finally breaks free, it moves a bunch.

Obviously, it depends on the amount of friction between the fault zone surfaces. I can't recall the name now, but there's a town* in California that sits right on top of the San Andreas fault, and they never get big quakes. Geologists think they know why; there's a huge deposit of chalk talc in the fault zone, which lubricates the strike-slip motion of the fault in that region.

I remember seeing a photo of a curb that runs transverse to the fault line in that burg. It has sheared and offset by several feet over time, marking a great deal of movement. But because the chalk moves easily across itself, it all happens so smoothly and so gradually that it never makes big jumps...meaning, there's plenty of motion there, but it doesn't happen in fits and starts. Hence, no quakage.

*UPDATE: The town is Hollister, CA.

jocolor


Last edited by Vito on Sun Feb 10, 2013 3:53 pm; edited 1 time in total (Reason for editing : Updated.)
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Kyle Weiss

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PostSubject: Re: Tectonic unrest   Fri Feb 08, 2013 3:32 pm

I look at faults, and for good reason, when I work, Veet. The old ones tell a story about where water, fluid and gasses have pushed the minerals I seek. Cool

Earthquakes are a huge mystery. Rock type, movement, pressure (orbital, gravitational, plate-to-plate) all have a factor to play. Smaller faults have all sorts of buckling, breaking and moving going on, and Nevada's full of 'em. They are a little harder to study, but talking to vulcanologists and seismologists in my neck of the woods has revealed quite a bit. Fascinating stuff. With the Basin and Range systems here in this area, often earthquakes are a result of whole range cleavage pushing wedges of rock up (or down) making for some cool ground-shaking.

I wish I could find that amateur video of someone on the highway that captured a large fault (not sure if it was San Adreas or not, sure looked like it) during a quake...this miles-long plume of dust just poofed out of the fault line, and it was dramatic. I like it when I'm reminded I'm a puny human and there's much bigger stuff going on. Twisted Evil
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Vito

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PostSubject: Re: Tectonic unrest   Fri Feb 08, 2013 3:38 pm

Starting at 1:37, this video shows the examples where the fault motion is smooth (as referenced in my previous post), but in this particular segment, they don't name the town, or explain the reason:



jocolor
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Kyle Weiss

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PostSubject: Re: Tectonic unrest   Fri Feb 08, 2013 3:41 pm

I know of that one...sheesh, I wish I could find the video that I mentioned...grrr... lemme keep looking. It's impressive.
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Kyle Weiss

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PostSubject: Re: Tectonic unrest   Fri Feb 08, 2013 3:51 pm

I found a terrible copy of it. Baja, Easter 2010.



Here's some others...





I bet the repenting was in full force that evening. Laughing

Cool
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Vito

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PostSubject: Re: Tectonic unrest   Fri Feb 08, 2013 4:17 pm

Kyle Weiss wrote:
...I bet the repenting was in full force that evening. Laughing

Cool
Yeah, that's a hoot. But the fun is somewhat diminished by the fact that such superstitions are so ubiquitous.

I'm still looking for the original video too. I think it's something I watched on Netflix...like a Discovery, Nova, or NatGeo thang.

jocolor
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Rob_In_MO

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PostSubject: Re: Tectonic unrest   Fri Feb 08, 2013 4:25 pm

Living near the New Madrid fault line and on top of an area that has been extensively mined, I keep an eye on these things too. Shocked
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Kyle Weiss

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PostSubject: Re: Tectonic unrest   Fri Feb 08, 2013 4:26 pm

Rob_In_MO wrote:
Living near the New Madrid fault line and on top of an area that has been extensively mined, I keep an eye on these things too. Shocked

Geologically, that's a fascinating area. Very active.
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Rob_In_MO

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PostSubject: Re: Tectonic unrest   Fri Feb 08, 2013 4:28 pm

Kyle Weiss wrote:
Geologically, that's a fascinating area. Very active.

When it decides to 'really act up' again, I'll give you a full report (once communications are restored).
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Vito

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PostSubject: Re: Tectonic unrest   Fri Feb 08, 2013 5:16 pm

Rob_In_MO wrote:
Living near the New Madrid fault line and on top of an area that has been extensively mined, I keep an eye on these things too. Shocked
I've delved into some of the history of that area, Rob. Major seismic stuff has gone down there for a long time...changing the river's course, sand volcanoes, and other interesting stuff (geologically speaking). The big 1811-1812 quake swarm didn't take a huge toll because of the relatively sparse population then. A repeat temblor of that magnitude nowadays is not going to be a whole lotta fun.

Makes me wonder whether folks there are taking earthquake preparedness seriously. We do here (...well, some of us, anyway.) I've got steel in all the structures I've built, bookcases and china cabinets bolted to the wall, an emergency generator and spare fuel, lots of candles, oil lamps, radios, batteries, wood for the fireplaces, enough food and bottled water to last for several weeks...and of course, plenty of duct tape.

jocolor
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Natch

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PostSubject: Re: Tectonic unrest   Fri Feb 08, 2013 7:23 pm

Rob_In_MO wrote:
Kyle Weiss wrote:
Geologically, that's a fascinating area. Very active.

When it decides to 'really act up' again, I'll give you a full report (once communications are restored).

Just took a break from writing up our first exam for the semester, covering.....(drum roll please....) plate tectonics, earth processes, and natural disasters. Rob, I've had a couple of my students end up working for FEMA, Arkansas Disaster Management (no, that's not our state budget office!) and related agencies. One did a fantastic project for his honors course on wireless communication in Memphis post quakes of various magnitudes. Basically, every transmission tower is on the ground and all the repair parts are in-accessible. Remember, pretty much every bridge is also gone, so the engineer may be just a few miles from the parts needed, and a few more from the transmission site, but you're not driving more than a mile or so (to the first little creek) and you ain't getting further for perhaps months or longer (other than on foot). Another helped develop the emergency protocols for my community in the event of a major quake. We're primarily a triage center for aid going in and injured, homeless coming out. Although, our water, sewer, electricity, gas lines and roads will also be down for several months to a year or more as well, but at least most of our buildings should survive. When we built our house, I got the biggest backhoe in the county and dug down to bedrock for my foundation, so the house should (with some level of damage) not fall down.

The New Madrid isn't really that active (on a global scale) but it's location is about as dangerous as you can get. It's an ancient fault burred under almost a half mile of saturated mud (which the Mississippi has laid down since the end of the last ice age) and nothing shakes more than unconsolidated sand and silt that is completely saturated. You don't want to be on Mud Island when the next big one hits (or Memphis, or St. Louis, or any place in the neighborhood). I've flown over the area a couple of times in a Piper and you can still see the sand blows in the fields from 1811. Those quakes rang church bells uncontrollably in Boston and cracked sidewalks in New York half a continent away. Fortunately (for me, at least) there are several transitional geologic layers between us and the fault, so even though I live less than 150 miles from the fault, we'd feel it less than 500 miles or so to the east.

The building laws regarding seismic resistance are non-existent in this part of the world. We're way behind San Francisco and most of coastal California, and way, way, way behind Japan. But that would be expected when a natural disaster is a rare event. If it happened often, people would be prepared.

I predict (the oracle bones tell me so!) the next really big one will be just east of Tokyo. Arguably the most dangerous location on earth for a major city, (three converging, rapidly moving plates coming to a point about 50 miles off shore, think mega earthquake followed by mega tsunami). That would be an economic disaster for the world.

Ain't life fun?

Natch
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Vito

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PostSubject: Re: Tectonic unrest   Fri Feb 08, 2013 8:24 pm

Natch:

I guess that answers my question: There are a relatively few people who are taking preparedness steps, but it sounds like the vast majority of folks who live in the New Madrid fault zone are in for a rude awakening.

We're a little better off here in SoCal thanks to the constant reminders provided by our numerous fault systems, but there will still be a wide disparity in Mercalli scale effects. The most immediate problems will occur in those areas built on sedimentary soils or poorly consolidated fill, where liquefaction is a certainty. Those areas include some of the greatest concentrations of industry and commerce. If The Big One™ hits during business hours, it's not going to be pretty.

Up here in the hills, we're on siltstone and sandstone bedrock. In the California Dep't of Mines & Geology Earthquake Planning Scenarios (8.3 Richter on the San Andreas fault, 7.3 on the Newport-Inglewood fault) for this area, we'll sustain Mercalli 7 damage at the worst—cracked stucco, loosened drywall, but no significant structural damage. Five miles away, down in the valley, they'll be looking at Mercalli 9 or worse, especially for the oldest buildings, which will suffer complete structural failure.

And those are older scenarios. The relatively recent (1999) discovery of the Puente Hills thrust system has the emergency planners scrambling. It's a system of blind faults that runs west from the Puente Hills and right under downtown Los Angeles. The older scenarios didn't plan for that, which means that the seismic building codes that covered most of the existing construction were inadequate. And most of the L.A. basin is built on sedimentary soils.

Uh-oh... affraid

It's not gonna be a whole lotta fun. If a quake hits during the day, it will be a mess. As you obviously know, the epidemic of serious injuries will be compounded by the destruction of infrastructure. Apart from the loss of electricity and gas (and the danger of fire from ruptured gas lines), there'll be loss of water (nothing to fight fires with). Add to that the loss of sanitation facilities, and the shit will literally hit the fan.

Thanks to many hard lessons learned from the 1994 Northridge quake, there has been an ongoing program of reinforcing bridges and highway overpasses, which will help keep the roads open, facilitate repair and emergency services, and greatly accelerate the resumption of normal activity. But any way you cut it, it's going to be a disaster that will affect the whole country. The disruption of port activity alone at Long Beach and Los Angeles will devastate the southwestern U.S. economy, and will have significant consequences for the rest of the nation as well.

jocolor
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Rob_In_MO

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PostSubject: Re: Tectonic unrest   Fri Feb 08, 2013 11:05 pm

Natch mentioned something that I've always found interesting and keeps proving itself again and again during disaster situations - communications (or lack of) during a disaster situation.

Time and time again, with us living in the modern wireless/digital world, when something happens almost all communications go down. Cell Phone towers are overloaded, backup systems are good for a week, damaged stations and repeaters prevent emergency calls from getting through, etc.

The one thing that works as good today as it did 60-years ago is Ham Radio. When bad things happen and normal communications are down, Ham Radio still gets through. When Katrina hit over 75% of all communications from the affected areas to the outside world took place on or through Ham Radio.

I'm not an old codger, I'm all for cell phones and digital communications. But - during any type of Emergency Preparedness, this factor should be not only considered but should be implemented into the plan.

Let's face it - Ham Radio works even when everything else quits.
Sometimes newer is not always better...



And Natch - I'm about an hour S/SW of St. Louis. Geographically it's the same distance to St. Louis or Cape Girardeau, MO.
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PostSubject: Re: Tectonic unrest   Sat Feb 09, 2013 2:40 pm

New Madrid is pretty darned active. No, it isn't as active as Himalayan strike/thrust action, which is continuous, but the potential for massive slipping is debatably greater than even California. Quiet but active faults would and should worry folks more than ones that move about freely. Complacency is a tough thing for people to move beyond. The good thing about constant quakes is people anticipate and build for them...the danger is only lessened by proactive approach, wherein New Madrid residents are probably going to be headlines of a midwest disaster. California might get bigger and more quakes, but they're ready.

Reno's in the same boat. There's evidence of quakes as recently as 3,000 years ago that might have been as large as 7.0 MMS. That's one way to get rid of the downtown casinos. Laughing

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Vito

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PostSubject: Re: Tectonic unrest   Sat Feb 09, 2013 3:31 pm

Kyle Weiss wrote:
...as recently as 3,000 years ago ...
That statement jumped off the page at me. You're a mutant, Kyle, and I hope you know that's a compliment. To you, 3,000 years ago is recent. That bespeaks a genuinely long-term perspective. Most people I know think five years is "long-term".

jocolor
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Kyle Weiss

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PostSubject: Re: Tectonic unrest   Sat Feb 09, 2013 3:51 pm

Hahaha, no kidding. 3,000 years to me, talking to rocks as I'm known to do, is yesterday's lunch. Hell, two breaths ago, in the longer outlook. *sigh* Time is a tube where things get bigger and smaller, not nearer or farther away. I think we talked about that once. Very Happy

Then again, stock trading these days means anything held more than a month is "long term." My six-month old computer is "old," and watching 30 minutes of television is "experience."

No wonder I like rocks, the big one we're adhered to especially. Fun place.

I am very, very small. I like it that way.

Cool
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Vito

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PostSubject: Re: Tectonic unrest   Sat Feb 09, 2013 4:05 pm

Kyle Weiss wrote:
...I am very, very small. I like it that way.

Cool
It takes a big man to admit how small he is.

jocolor
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Kyle Weiss

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PostSubject: Re: Tectonic unrest   Sat Feb 09, 2013 8:38 pm

Word. cheers


I love you,

-- Mutant Weiss
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PostSubject: Re: Tectonic unrest   Sat Feb 09, 2013 10:12 pm

And........

Here in the Puget Sound region, we are apparently due (or overdue, depending on how you read the stats) for a significant event of 9.0 or greater, based on geological history.

We are literally criss-crossed with hundreds of faults. Saw a map of this a while back and it was impressive!

In fact, one fault line runs more or less directly under my neighborhood. Could be right under my house aamof!

Shocked

Apparently, these would be the worst kind too. Large, shallow thrust faults which would shake the ground for several minutes and produce 20' displacements. Major damage would be wrought in heavily populated areas of Seattle.

And a Tsumani would also affect areas in the Puget Sound, despite its distance from the Pacific Ocean.

The local media does much to warn of this on a regular basis. In fact there was yet another news piece last night.

All the same, I recognize that the media has to sell air time. And doom and gloom sells more than warm fuzzy stories. Be that as it may.

All to say that I'm aware that my region is on the crosshairs of a major seismic event, possibly in my lifetime.

Been through several shakers since I've lived here. Last big one was in '01.

That was a 7.1..........and while it didn't produce any casualties and terribly significant damage (depending on one's POV) it did get our attention.

Suspect

The details of this one will be for another thread. Don't particularly want to revisit it just now..........

Evil or Very Mad

Hopefully I won't live here when the "big one" hits...........

affraid


Cheers,

RR

















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Vito

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PostSubject: Re: Tectonic unrest   Sat Feb 09, 2013 11:12 pm

Brewdude wrote:
...we are apparently due (or overdue, depending on how you read the stats) for a significant event of 9.0 or greater, based on geological history.
Aaaccckkk!!! That 9.0 stuff is serious bizniss, RR. affraid

I see that the Puget Sound area is now featured on the USGS "Shakemap":
Glad to hear you folks aren't being complacent up there.

As you probably know, the tsunami risk in your area comes from the motion of the Juan de Fuca plate, which is sliding under the North American plate. The subduction zone starts well offshore, but that's the problem. When the North American plate won't let itself be pulled down any farther, it will snap back up, and...ZAH!! It's tsunami time.

The full force will hit the western side of the Olymplc peninsula, but Puget sound won't escape. Wave motion is weird. Waves wrap around obstacles. The tsunami will bend around Cape Flattery and roll through the Strait of Juan de Fuca. It will eventually push its way around Victoria to the north and Port Townsend on the south, picking up amplitude as it crowds through the increasingly narrower passages, especially the channels into Puget Sound. It will be a good idea to get to higher ground.

Motion along the faults that run inland present another hazard, and I don't envy anyone who's anywhere near a 9.0 magnitude quake. Anyone who's been in a big shaker knows that the relatively puny forces we self-prepossessed humans can muster don't amount to a phart in a hurricane compared to what the Earth can do. Once you've experienced it, it'll make a real Boy Scout outa you: "Be prepared."

jocolor
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Harlock999

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PostSubject: Re: Tectonic unrest   Sun Feb 10, 2013 4:14 pm

Sorry guys,
But every time I read the title of this post, it reads "Teutonic unrest" in my head, and I start thinking "oh no, not again!?" Rolling Eyes
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Vito

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PostSubject: Re: Tectonic unrest   Sun Feb 10, 2013 4:55 pm

Harlock999 wrote:
...every time I read the title of this post, it reads "Teutonic unrest" in my head, and I start thinking "oh no, not again!?"
Yeah, I noticed that too after I started the thread. Yet, miraculously, the thread has managed to (mostly) stay on topic, without devolving into any-onic unrest...Teutish or otherwise. Wink
________

Linked below is a letter to Nature documenting core drilling observations of fractured serpentinite in the locus of the San Andreas fault south of Hollister, CA. (I have updated my earlier post in this thread.)

http://www.nature.com/nature/journal/v448/n7155/full/nature06064.html?free=2

The core samples show the presence of talc, which the geologists believe accounts for the "creep" in the fault zone in that region, wherein the Pacific plate moves (relatively) continuously. That is, the fault moves easily in frequent, small increments, gradually releasing seismic tension. The talc acts as a lubricant between the tectonic plates in that area, so they never stick together tightly enough to accumulate enough tension to be released as an earthquake.

The geologists believe that explains why Hollister never has any earthquakes, even though the San Andreas Fault runs right through the town, and the evidence of plate motion is obvious.



I snagged the image from the video at the following link. The narration is loaded with sensationalism that should embarrass The History Channel. But it does contain some interesting information about how the San Andreas fault was discovered.

http://www.youtube.com/watch?v=jzc4sdbHjig

jocolor
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