7.1 magnitude earthquake strikes Southern California
latimes.com
latimes.com
This isn't entirely accurate. While it's "score" was higher, the magnitude doesn't account for things like the type of fault, the type of movement, the depth, the soil, the duration of movement, etc.
Northridge was far more severe than this one, with an "apparent magnitude" greater than 9.
Don't get me wrong, this one sucks for all the people affected, no doubt, but as someone who lived through Northridge very close to the epicenter, it's sort of personal to me.
A lot of this also has to do with how close to populated areas the earthquake is, and if the same quake happened today, the damage would be much less due to better construction.
Not sure how to compensate for distance, but my gut feel says that's about equivalent to a 5.9 in SF itself?
That's overstating things by quite a bit. There was severe damage and fatalities but 'destroyed a lot of San Francisco' was 1906, an estimated 7.9 followed by fires.
PS: I lost my proverbial "I survived the Loma Prieta in San Jose" t-shirt. Lost half a swimming pool, bookshelves, dishes and so on... our furniture was anchored to the wall studs and computer monitors and other electronics were industrial Velcroed to surfaces.
destroyed a lot of San Francisco
Almost killed my friend, who just happened to move his bed away from the bookshelf the day before. The bookshelf smashed to the ground right where his bed had been.
We also had to dig my grandparents out of their house with shovels.
We got shovels and started digging, calling out their names. Finally got the back and found them sleeping in the pull out sofa! We packed some of their stuff and took them back to our house since we had minimal damage (despite being thrown from bed) and then went back later to survey the damage.
At that point people in the larger multi-family buildings had all evacuated and set up tents in the median strip on the main street (Ventura Blvd). Many of those buildings were condemned.
My neighbours - well, lets just say that by the time I got my senses together to go outside and inspect things, they'd already packed all their shit and their kids into the SUV and were moving back to Oklahoma that instant, no time to wait - they GTFO'ed out of California... their house wasn't even that damaged, apart from its chimney laying in the street, like every other brick chimney in the neighbourhood ..
Northridge was wild. I'll never forget the feeling of walking around Hollywood that morning, looking at the kitchen and toilet sections of apartment buildings that had their walls stripped off them, like some bear had ripped open a beehive to get to the goods ..
I could never sleep under a mirror for exactly that reason.
The magnitude scale that is most used is an expression of the total energy release in the earthquake is called the 'moment magnitude' or 'work magnitude' because it's measured in those units (Newton meters or dyne-cm). It is calibrated to be similar to the original Richter scale, which was an empirical, I believe unitless, scale based directly on seismometer readings. If someone credible says that an earthquake is a 3 or a 7 or something, they are almost certainly referring to the moment magnitude. The 1989 Loma Prieta event was a M 6.9 event, Northridge was M 6.6 or 6.7.
There is another measure called the 'intensity' that you may be referring to with the 'apparent magnitude' reference. This is a non-quantitative, basically ranked categorical description of the amount of ground shaking and subsequent damage that occurred. The most common intensity scale is the Modified Mercalli intensity scale; it is usually (and correctly) denoted in Roman numerals. The Wikipedia page for the Mercalli scale [1] is good, however I prefer [2]. The intensity has a sort of tree-falling-in-the-woods element to it: the categories are based on how people and the built environment respond to the earthquake, so did earthquakes in the 4.6 billion years before humanity have intensities? They had magnitudes.
Quantitatively, ground shaking is measured as 'peak ground acceleration', a force, usually compared to gravity 'g' (i.e., 9.81 m/s^2), as 'peak ground velocity' which is a velocity (m/s), or as 'peak ground displacement' which is a distance.
The intensity of an earthquake will be related to the peak ground acceleration and velocity, as well as the duration of the shaking. These are functions of both the earthquake properties (magnitude, faulting style, depth) as well as the properties of the ground in the region of the earthquake, and the distance from the earthquake (as the amplitude of the waves decreases with distance). Solid rock does not shake nearly as much as loose or wet sediment, for example, and some geologic basins that are deep pockets of sediment surrounded by bedrock can amplify earthquake waves and make the shaking locally much worse than it was elsewhere, even closer to the earthquake. This was a big deal in Loma Prieta, for example--the damage in Oakland, built on water-saturated sediment, was worse than in some of San Jose, or in my (current) house in the Santa Cruz mountains just a few km away (I was safely dodging tornadoes in Tulsa at the time).
[1]: https://en.wikipedia.org/wiki/Modified_Mercalli_intensity_sc... [2]: https://www.mcsweeneys.net/articles/levels-of-the-mercalli-s...
As I said, I was up coding all night. At the time I had a U-shaped desk flanked on all sides by bookcases full of books. Lots of databooks filled these shelves (for software guys: These are books published by chip makers containing their catalog of chips and technical details on each one).
I was working on a the microprocessor code for a high power motor control. The hardware, 100A power supply and test equipment where all on my desk, turned on and operating. I was using a very large ceramic wound resistor in a bucket full of ice as a test load. The bucket was on the floor and connected to the motor driver via very large conductors (think jumper cables).
At 4:31 AM I felt a single jolt. I know because that's when I looked up at the digital clock up on the shelf immediately in front of me. It was a Radio Shack clock with red LEDs for the digits. It was part of their home automation system, with buttons on top to turn on and off various satellite plugs, lights, etc.
The jolt felt like The Hulk shoving the house or something like that. One sharp short jolt. My first thought was "this is going to be bad". I had been in a couple large quakes but this jolt had a different feel to it.
That's when it started. And what was bad about it is that the vertical component was significant. Well, significant enough to launch me and every single book and object on my bookcases straight up into the air. The compressed air spring in my chair acted like a pogo stick. I literally got launched upwards, I'll guess at least a foot, if not more.
My last memory of this portion of the event was floating in space with all of my books in the air at the same time. It was very, very weird. Power went out, I fell to the ground and so did everything else around me. The shaking was violent, as I said before, like a train going through the house.
Thankfully the motor driver wasn't hot because I was not driving the load at the time. It ended-up on the floor buried under a pile of National Semiconductor databooks. That would have easily been a fire had the thing been hot and power not gone out.
I later found a massive 8 inch drive that was on a shelf across the room landed just inches from where I fell to the ground. That thing could have sent me to the hospital. Amazing.
I still have the clock somewhere.
Can't see your contact details anywhere, so using a comment here instead. ;)
I didn't even feel the one yesterday either.
My daughter kept saying she wanted to go see the earthquake. I think she thought it was outside.
> “The mirror shaking was easy … put a little vibrating motor in and shook it.” Lantieri said. “But the water was another story. It was a very difficult thing to do. You couldn’t do it. ”
> “In order to replicate that for the eventual shot, they “fed a guitar string through the car, down to the ground, and then I had a guy lay under the car and pluck the guitar string,”
https://www.businessinsider.com.au/jurassic-park-water-cup-2...
More info in this article (linked to from the one above): http://temblor.net/earthquake-insights/southern-california-m...
Point is, I wonder if this was the sound of Badwater Basin (lowest point in North America) getting a little bit lower...
In the meantime, I wonder if there are any good photos of them? I wouldn't know what to search for.
These hikes aren't nearly as hot as the valley, and probably manageable even in the summer. Much of Death Valley's heat comes from the air being more compressed the lower you go, so if you're 6000 ft up it's not that bad at all. Although, be careful.
Here's some pictures I found online: https://www.americansouthwest.net/california/death_valley/wi... . Note that the rock below you has clearly toppled over to almost a 45 degree angle. All the mountains in the distance are like that also.
A few hours later I was on a different ridge and a bunch of fighter jets flew through a canyon _below_ me. Death Valley is awesome. (although that may have been right outside of it?)
Today's earthquake was a strike-slip earthquake, where two parts of the crust slide laterally by each other on a fault plane inclined close to vertically in the crust. The fault is probably oriented NW-SE [1], parallel to the San Andreas fault, although from the pattern of energy release from the earthquake (known as the focal mechanism[2] or moment tensor[3]) it also could be on a NE-SW oriented fault, with the direction of shear being the opposite. Because this was a strike-slip earthquake on a vertically-inclined fault, there won't be more than a few cm of uplift or subsidence of any parts of the earth's surface.
The domino-style faulting that occurs in the Basin and Range of the US, basically from Owens Valley to Salt Lake City, is an expression of 'normal faulting' (rather than strike-slip faulting). Normal faults are inclined from the horizontal, and the block of crust above the fault slides down the fault, like down a ramp. After a lot earthquakes (hundreds to thousands of M6+ earthquakes) the blocks have rotated on a horizontal axis quite a bit, so that they are no longer upright [4]. Furthermore, and quite importantly, as a result of this faulting, the crust (or at least the upper crust where the faulting happened) is both thinner from top to bottom than it was previously, and wider than it was previously--we say that the crust got 'extended' because it is horizontally lengthened/widened. You are absolutely right that Death Valley is forming in this kind of environment.
There are two main reasons for crustal thinning and extension. One reason is that the boundary of that part of the crust moved away, so the crust stretched or extended to fill the gap. The other is that the crust was too thick and high, so it spread out. The continents are kind of like rafts of granite floating on more dense, hot, ductile rock below (the mantle). The density contrast between the lighter crust and the mantle is sort of like icebergs floating in sea water, so most of the continents are below the surface of the ocean basins. When a big mountain range is built that gets high, it also has to have a thick root to support its surface elevation, like the undewater part of an iceberg. However, the crust isn't always strong enough to support a big mountain range for a long time, and so it will break apart under the force of gravity and spread out laterally, reducing the gravitational potential energy contrast between the (formerly) high mountains and the surrounding lower elevation crust.
It is thought that in the western US, both processes (the moving boundary condition, and the gravitational collapse and spreading of the crust) have been the cause of the crustal extension that produced the domino-style block faulting. The big collapse was probably during the Miocene, say about 15 million years ago, which produced a lot of the faults and smaller mountain ranges that we see today. Many geologists think that California was one or two hundred kilometers closer to Colorado, and the area that is now Nevada and western Utah was narrower and much higher--say a mean elevation of over 10,000 feet. This has been nicknamed the 'Nevadaplano' in reference to the Altiplano of Bolivia and Peru, which is an analogous geologic feature. I think that there is also a slight component of extension between the North American and Pacific plates at this latitude, i.e. the Pacific plate is mostly sliding by North America on the San Andreas and parallel faults, but it might also be moving away from North America (i.e. Kansas) at a few mm per year.
[1]: https://earthquake.usgs.gov/earthquakes/eventpage/ci38457511...
[2]: https://en.wikipedia.org/wiki/Focal_mechanism
[3]: http://seismo.berkeley.edu/~rallen/eps122/lectures/L12.pdf
https://www.fema.gov/media-library-data/20130726-1728-25045-...
When the first quake happened, I did run. But it didn't really occur to me that we'd had an earthquake until after. It was like I was auto responding to an emergency, but the mind hadn't had time to process that it was an earthquake.
And, this is considering the fact that we'd sort of known that a big one was due soonish.
It should contain all your valuable documents, medication if you need it, first-aid kit, spare water bottles, emergency food and water for 5 days, backup cell device, etc.
Nobody living in a quake zone should be content with themselves unless they have a proper bug-out bag prepared .. you don't want to be fighting for scraps in SoCal after a big quake.
(I once watched two little old ladies - grandma's - beat the shit out of each other in a 711, fighting over the last bottle of water on the shelf..)
It's like what happens to thunder when it's far away.
Any HN regular should be able to study for a few hours and pass the Technician test. This gives you access to all the VHF and UHF frequencies that are often used in emergency communications. A bit more study and you can get the General license, which lets you use more HF (potentially longer range) frequencies.
Here is a good place to start:
Many hams start with a cheap Baofeng handheld. These sell in the $25-60 range. Here's one I have and recommend - it's at the high end of that range but has several improvements over the cheaper ones including a better antenna:
https://smile.amazon.com/dp/B01J2W4JUI/
Ham radio has been popping up on HN a lot lately. Besides emergency communications, there are a lot of interesting things you can do once you get your license. Feel free to holler with any questions!
I have probably a dozen RTL SDR’s strewn about boxes and junk drawers, but the idea of relying on them in an emergency is unsettling. The little baofengs have a terrible interface but last a long time on a charge and are pretty rugged.
The point about practicing is legit. Most comms with these radios happen with relays, but you’ll want to know where people will be in simplex (walkie talkie style) operation if there’s no infrastructure.
This isn’t hyperbole. I got my Technician license after literally only studying for an hour (admittedly I had some prior experience, but most of what the test is just memorizing various things you should know).
Maybe the proliferation of more 5G towers could make the internet more resistant?
Relatedly, remember when long distance vs. local was something you had to consider when making a call? Hahaha.
Random notes:
- The epicenters tends to be relatively close (<20 miles) and relatively shallow (<10 miles).
- I think the 7.1 brings this into the territory of stronger than we had growing up.
- I've seen people mention that it didn't impact a densely populated area. Normally I feel the same relief about that except this time I know the people which brings a different perspective
- My biggest concern is for those who were evacuated from the hospital in the 100 degree weather. A childhood friend's dad is bedridden, trying to recover, and is now out in the heat.
- I've seen reports of roads to towns like Trona being closed off. Unsure if that is all routes and how long until they re-open but that is probably my next biggest concern.
"Scientists said it the fault causing the quakes appears to be growing."
First time felt earthquake .. Surreal experience
Its very important to work on ones mindfulness during quakes.
- how to spot "unreinforced masonry" in order to avoid it?
- why is a strong table to be looked for inside, to get underneath it?
- I would imagine basements are bad to be in, is that so?
- I would imagine upstairs is a bad place to be too, right?
- does the ground really split underneath your feet?
Modern buildings don't usually completely collapse ("pancake"), and being under a sturdy table can absorb the weight of partial collapse: as an example, an interior wall collapsing onto you. See [0].
> I would imagine basements are bad to be in, is that so?
All I know about this is that having a (code-compliant) basement makes the entire house more resilient, but I couldn't find anything about being _in_ the basement during an EQ being good or bad. Know that basements in low-density structures are quite scarce[1] in Southern California, though -- I've lived in LA for four years and don't remember ever being in one, except in large apartment buildings.
Don't try to get out of a basement if you're in one when an EQ hits. Most injuries are a result of people breaking their ankles and legs trying to move while the ground is shaking.
> I would imagine upstairs is a bad place to be too, right?
It's a tradeoff. In the event of a structure collapse, you have further to fall but less structure to fall on top of you.
> does the ground really split underneath your feet?
Yes, if you're straddling the fault line and standing near the epicenter. (You won't be doing that).
There has never been a confirmed case of someone falling into an "earthquake chasm", but it might be something to worry about if you're a cow grazing in a Bay Area field[2].
---
Take a look at this study[3] of the 74 deaths caused by the '94 Northridge EQ. It's the best data we can use to project what would happen if a major EQ hit LA today.
[0]: http://www.cnn.com/2013/07/04/tech/innovation/the-earthquake...
[1]: https://www.latimes.com/home/la-hm-basement-side-20150509-st...
[2]: https://www.realclearscience.com/blog/2013/01/do-people-ever...
Maybe tomorrow will be the day...
I've found Google's AI to be significantly better than Siri.
Do NOT get in a doorway, unless it is one without a door. The door is more dangerous than any other damage.
Do NOT run outside, unless it's faster than getting under a table. And if you do go outside, get away from power lines.
* bathrooms with plumbing in the walls are supposed to be a little stronger.
* blankets can help protect you from breaking windows.
* if you are outside, watch out for trees, powerlines, things falling off buildings (tile roofs, pots), esp. brick buildings
It’s definitely not something you want to run on.
In Japan, they have earthquake simulators that drive this point home. The old version is a truck whose bed is fitted with a simulated apartment on hydraulic shakers. The newer version is VR.
Your second concern is fire. In Japan, gas is always run through a sensor that cuts the line if shaking is too intense. I’m not sure if California has the same. If there’s a gas leak nearby, that’s the next serious danger after falling objects.
> The quake caused further damage to a U.S. weapons testing facility outside Ridgecrest, the Naval Air Weapons Station China Lake, although details were sparse early Saturday. “NAWS China Lake is not mission capable until further notice; however, security protocols remain in effect,” the naval base said on its Facebook page after the latest temblor. The installation is the Navy’s largest single landholding, sprawling over 1.1 million acres, an area larger than Rhode Island.
But yes, AFAICT from the maps, the epicenter was basically right under China Lake.
The Naval Air Weapons Station China Lake in Ridgecrest was evacuated and deemed not "mission capable" https://ktla.com/2019/07/06/naval-air-weapons-station-china-...
Animals sometimes can feel earthquakes coming. Little is known about this but it is suggested that it has to do with electromagnetic fields.
We experience problems on earth when there were bug sun flames.
Could a big earthquake influence our communications?
The windows and doors were creaking and making loud cracking noises. Both times it felt like an unbalanced washing machine on a different floor.
Here in Los Angeles we felt it for sure but a quick survey of friends around town indicates that there wasn’t much damage.
That said, it does look like there was some damage from this one. The news is showing videos of burning buildings
I hope someday at least the Internet works on UTC :)
back to 7.1
Outside US it's Antarctica, but it sounds rather inconvenient..
Not to mention the risk of "Florida man".
https://pdfs.semanticscholar.org/6f7e/ce3f7045e645f6b5891a80...
Make sure to have a backpack with some essential items there. Have some gallons of water and make sure to have a plan in the eventuality of an accident, for example, make sure to close the gas main valve. Sync with your family on where to gather if they are at work/school, etc.
I was there for the 9.1 @ Chile in 2010 and all of this was super helpful, within 10 minutes my whole family was gathered in our parents house and we were already saving water in our bathtub and pans (which was super handy, because we had no water for about 3 weeks)
Infrastructure or buildings? Wood-frame buildings without a soft story are pretty safe, at least in terms of not killing you.
I always imagine water pressure being lost right away, so if you didn’t have water already stored you’d be SOL
Pressure in the “customer end” of the water supply network will still be available for a little while (minutes to hours) in the event of damage but damage will take time to repair and the impact of the damages ongoing effect and the time to repair make one of the most basic survival tips for the average person not otherwise maintaining survival supplies: “fill the bathtub and anything else you’ve got”. You might have 15 minutes before the broken pipe washes away enough dirt that pressure drops enough to stop the flow from your tap.
> Jumpstart is a surplus lines insurance broker working in full compliance with applicable insurance regulations. The insurance described here is effected with certain Underwriters at Lloyd's, London.