Earthquake early warnings.

[Ianab]

Was relaxing here at home last night (about 9pm) when the phone gives an unusual "bleep". Glance at it, and it's an earthquake warning to expect moderate shaking from a mag 5.5 quake situated about 100 miles South. 

Nothing happened for about 5 seconds, then we got some mild shaking for about 10 seconds. Turns out to be a 5.8, but deep and out at sea so no damage, but widely felt over most of the country. 

But it was a bit freaky getting told about the quake before it started. The propagation time for the quake gives enough time for it to be picked up, measured and a warning sent out to every phone in the area it's expected to affect. 

[Dan_Shade]

That's very interesting.

I've only experienced one earthquake, it was quite interesting. 

A bit of notice could make a difference in people's safety. 

[bigblockyeti]

That's impressive they're able to predict the speed of the quake through the ground.  Sound (movement) through air is pretty fast, way faster in water and I expect quite a bit more so through this ball of dirt and rock we live on.  I'd be interested in seeing the time between detection which would obviously be at least a little time after it start, then how quickly data can be compiled then warning messages sent out.  No doubt it could certainly help saves someone's life!

[rusticretreater]

The seismometer equipment today is really sensitive, so they immediately know what is going on.  Since its all computers now, it can figure it out and trigger the emergency messages right away.  I saw a video where the guys doing strip mining were going to set off a long line of explosives to break up the surface for scraping.  They had to notify the officials and wait for everyone to be notified and the clearance to blast come back.  You can't hide a rocket launch, underground bomb testing or anything else from them now.

I get severe weather reports over the phone too.

[bigblockyeti]

My brother reminded me when he worked for GE Power in Greenville, SC, they had to notify local officials when certain events were going to take place.  They dropped something(?) that weighed 300T+ once and it only fell 4" but they got a call right away from the AHJ to see if it was them.  I suspect with an array of seismometers at known distances from each other, they can probably triangulate where a seismic event originated as well.

[barbender]

I hear there was a guy in SE Minnesota that pulled a stunt back when Tannerite was first becoming a thing. He loaded up an old dump truck with the stuff, shot it and set it off, reportedly blasting the truck apart. Well there is also the Prairie Island nuclear facility down in that area, apparently the detonation was detected by siesmometers and he soon had a visit from Federal agents😬😬

[barbender]

2008 story: Blast near Red Wing brings felony charges | Local News | republicaneagle.com

[Ianab]

That's impressive they're able to predict the speed of the quake through the ground.  Sound (movement) through air is pretty fast, way faster in water and I expect quite a bit more so through this ball of dirt and rock we live on.  I'd be interested in seeing the time between detection which would obviously be at least a little time after it start, then how quickly data can be compiled then warning messages sent out.  No doubt it could certainly help saves someone's life!

Doing some rough calcs, seismic waves travel through rock at about 5,000 meters / sec, about 11,000 mph. So would have reached our location about 30 secs after the quake started.  In that time the system had the approximate location and magnitude worked out and had sent out phone alerts. 
Now I saw it was a "only" a 5.x and relatively distant, so nothing to panic about. If it had been a Mag 8 I would have had time to dive for cover. Of course the worst quake is one that's shallow and close, where there is no time to send a warming. But in a big enough quake (or tsunami) the affected area is much wider, and some warning is going to be useful. 

NZ is "Ring of Fire" with  frequent earthquakes and several active volcanoes, so it's wired up with seismographs. Last time the Foo Fighters played a concert in Auckland the seismographs recorded it as a long lasting Mag 2 quake. Basically enough people dancing can be detected. 

[barbender]

Haha maybe we can start giving rock and metal bands a siesmometer reading rating. "Man that Slayer concert the other night registered a 3.1!"😂

[bigblockyeti]

2008 story: Blast near Red Wing brings felony charges | Local News | republicaneagle.com

I bet it was a heck of a party, probably a floating keg or four too.

[barbender]

Yeah I would imagine, "seemed like a great idea at the time"😂

[beenthere]

Sounds (no pun intended) like back in the 60's, a plan to use low frequency sound to communicate to subs around the world.

In the 1960s, US Navy officials concocted an ambitious plan: they wanted to bury a gigantic grid of cables under roughly 41 percent of the state of Wisconsin in order to turn its bedrock into the world's largest radio antenna.

https://www.vox.com/2015/4/10/8381983/project-sanguine

Called project ELF under the Sanguine project.

[Guydreads]

The incredible advances of tech these days never cease to amaze me. I can't say that they're all good, because they're not... But MANY are.

[charles mann]

I was at our airbase in trilahue, Chile in late feb of this yr, waiting on a fire call when i felt my room shake for a few sec. Thinking it was someone scratching their back on the corner of the conex, i didnt think anything of it. A few minutes later, the conex really shook, which i jumped up from the chair and went outside to tell whomever it was to STOP and noticed the ground and other conexes shaking. That was my first time in an earthquake. Found out it was centered about 75 miles to the east, in the mountains and was a 4.8. 

[rusticretreater]

In 2011, there was a 5.8 mag earthquake in Mineral, Virginia.  It occurred at the base of the Blue Ridge Mountains which then transmitted the shock wave up and down the Eastern Seaboard.  Vibrations were reported from Maine to Florida and as far west as the Mississippi River Valley.  The Washington Monument in DC was damaged due to the swaying induced.

I was driving on the interstate about 200 miles west of the epicenter at the time.  I remember seeing a nearby 18 wheeler swerve at the same time I was wondering what the hell was the matter with my car.  A few seconds later the phone rang with my daughter calling me scared to death as our house 60 miles north of my location was also shaking.

It was "only" a 5.8 mag quake, but it has been recorded as the most widely felt earthquake in the US due to the mountains transmitting the shock waves.

[Southside]

My wife was in Philly that day for work and felt it.  I did not feel it here on our farm.  

[btulloh]

I felt it. I was standing in the garage and it was a fair shaking for about 10 seconds. Not bad, but unexpected and startling for Central Virginia. Months later I found out that it tugged on the line to my underground oil tank and afterward it was only picking up the top half of the tank.

[Tom King]

That day in 2011, I was installing a kitchen in a house on the lake.  I heard what I thought was a big helicopter really close overhead.  I remember thinking it must have been a Chinook, but it sounded like it was running okay.

I looked out the window with the lake right in front of me to see if I saw rotor shadows on the ground, but didn't see any.  That lot had a wooden bulkhead.  The water was like glass, but I was seeing very smooth waves going out from the bulkhead, but none coming in, which I had never seen before.  Any waves going out off bulkheads had always just been bounceback waves from ones coming in.

Thinking that was strange as I was getting a farmhouse sink installed into position, I looked down at the sink, and bumped it with the heel of my hand to get it into position.  The Instant I bumped it, the whole house started rocking.  I knew what it was after a few seconds, but it was quite startling!

One helper was running a string trimmer outside, and never knew anything had happened.

[Don P]

We were working on a house built on a 3' deep gravel trench foundation that day. Michelle was up on a stepladder on top of a wheeled 2 buck high scaffold finishing the timberframe trusses. It woke up a retired friend down below us from a nap and he came to check us out. We never felt it. The only thing I could figure is the gravel under us absorbed the shake. If so and if it wasn't just us distracted, that would be worth investigating for shaky ground.

[Tom King]

Granite is real close to the top of the ground here.  The house I was working on is one of the few lake houses without a daylight basement.  They couldn't build one because the granite was too close to the top of the ground. 

I didn't build it, but it wouldn't surprise me if part of the foundation was sitting directly on Granite.  

The end of the house I was working in was part of a large great room with a high cathedral ceiling.  Probably made a pretty good speaker.