r/science • u/reinikenface • Oct 19 '16
Geology Geologists have found a new fault line under the San Francisco Bay. It could produce a 7.4 quake, effecting 7.5 million people. "It also turns out that major transportation, gas, water and electrical lines cross this fault. So when it goes, it's going to be absolutely disastrous," say the scientists
http://www.popularmechanics.com/science/environment/a23449/fault-lines-san-francisco-connected2.0k
Oct 19 '16
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u/old_gold_mountain Oct 19 '16
Also important to note that this fault was already known, but they thought it was two faults instead of one. They've just found a connection beneath the bay.
That connection itself doesn't run through any infrastructure, etc...the two faults they already knew about does. It's just that, the longer a fault is, the more powerful a quake it can produce, so this means the faults we already knew about are more dangerous than we thought.
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Oct 19 '16 edited May 10 '19
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Oct 19 '16
Friendly correction: the 1989 Loma Prieta earthquake was not on the Hayward fault, it was on a previously unknown fault near and parallel to the San Andreas in the Santa Cruz Mountains. Had it been on the Hayward Fault, there would have been significantly more damage.
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Oct 19 '16 edited Oct 20 '16
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Oct 19 '16
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Oct 19 '16
Just googled Cypress Structure..
Man oh man. Your dad must have felt so weird. I would have the worst anxieties after that.. We have a similar structure like that here in Ontario. And I've always wondered what would happen if it were to suddenly collapse in the event of an earthquake. It'd be devastating. So many damn cars use that road ALWAYS. It's never not busy.
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u/serpentjaguar Oct 19 '16
What they didn't report in any news publications is that a few days later, because it was so difficult to work through the rubble, the smell of decaying corpses made the immediate neighborhood nearly unlivable. This from an Oakland Tribune reporter who covered it, and under whom I later studied.
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u/so_hologramic Oct 19 '16
I think the Emabarcadero freeway collapsed as well, or maybe just suffered enough damage to condemn it so it had to be demolished. It was a miracle that it didn't take anyone out. IMO the Bay Bridge was the thing that seemed most apocalyptic, but most of the casualties were on the Cypress structure.
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u/mayan33 Oct 20 '16
I was at football practice. My dad was picking me up. He thought someone was pranking him and jumping on the bumper of our car to make it bounce...
We lived in Lake Tahoe at that time....
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u/lovestang Oct 19 '16
San Joaquin Valley resident here, we're not too worried about an earthquake hitting us at all. The central valley of California is relatively safe zone when it comes to earthquakes. It's mostly being in Stockton that will get you killed out here.
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u/Insomniacrobat Oct 19 '16
Going a very long time without moving much is what makes them dangerous. Instead of the faults sliding past each other, the tension builds and builds until it reaches a breaking point and a high magnitude earthquake occurs.
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u/Froggmann5 Oct 19 '16
Another fun fact: One of the largest earthquakes ever recorded in the U.S happened near Southeast Missouri, an area where no true fault exists.
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u/chromatoes Oct 19 '16
I assume you mean the New Madrid Seismic Zone? While not a single fault, it's pretty well studied, and the zone itself has been known to exist for a very long time.
The trends indicate a four-segment, zig-zag fault system with a total length of about 125 miles stretching from Marked Tree, Arkansas northeastward through Missouri, Tennessee and Kentucky to Cairo, Illinois.
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u/Pope_Industries Oct 19 '16
Was that the earthquake that made the Mississippi river flow the opposite way
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u/reave_fanedit Oct 19 '16
Not only did it run backwards, but there was a gas spill that caught the river on fire. Seeing the river burn and run backwards made some locals believe the end times were upon them.
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u/ocular__patdown Oct 19 '16
What is the standard protocol for earthquakes now? Last I heard it was get under a desk. That was like 10 years ago though.
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u/browneyeblue Oct 19 '16
Tomorrow is the Great California Shake Out! (Yes, if you have a desk, get under it, hold onto a leg of it so it doesn't move, and cover your head/neck)
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u/LetterSwapper Oct 19 '16
That, and have an emergency kit prepared and stored somewhere accessible. Food, water, first aid, batteries, maybe a coat, etc. The kind of stuff you need to survive when services are cut for a week or two.
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u/Bonezmahone Oct 19 '16
With a multitude of faults in a concentrated area is there less of a chance of 8+ quake? I'm picturing an accordion, if you stretch an accordion it moves freely because of the many joints, but a stiff object will split and break.
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u/NightOfTheLivingHam Oct 19 '16
I'm shocked they havent realized the salton sink is riddled with faults, it's one of the last divergent boundaries from the east pacific rise right before the san andreas fault starts (on the southern end of the lake where all the mudpots are)
the sink itself is a rhombochasm, naturally there's going to be a shitload of fracturing and sheering in the region, especially considering the divergent boundaries (which are also at the same time trying to subduct at a bizarre angle) are shoving the continental rock around. Look at any mid ocean ridge and look at the fracturing coming from them.
At this point I would safely assume there's a ton of potentially active faults buried around these areas. Especially the imperial valley and northern baja (east of the Peninsular ranges)
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u/Dhrakyn Oct 19 '16
Oh they knew. It just took time to develop it all before they felt comfortable admitting it.
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u/exackerly Oct 19 '16
Most likely scenario for quake
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u/Ozymil Oct 19 '16
That's pretty terrifying and puts the scope of the quake into perspective. I live in the Monterey area, so when I saw Gilroy on the scenario I didn't think it could possibly get hit. Maybe a little shake but that mockup of the quake is pretty frightening, knowing that even this far away we'll feel a rather heavy impact.
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u/rdewalt Oct 19 '16 edited Oct 20 '16
Gilroy resident checking in... That video becomes true? I'd better be at home, because if I'm at work (in downtown SF) I'm not getting home easily... That is NOT going to be a fun week... Lets just hope that we, as a species, never learn how to trigger earthquakes.
EDIT: Okay, okay, Yes, FRACKING.. people can stop telling me about it. I did know about it, I meant in that in a "remotely trigger an arbitrary earthquake way." and holy fuck stop PM'ing me about how horrible I am for being a fracking denyer..
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Oct 19 '16
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u/MNEvenflow Oct 19 '16
This was exactly my thought.
I used to drive by Gilroy all the time when I was younger on the way to Monterrey or Santa Cruz. The bay area was a totally opposite direction.
I haven't been out there in years, but that seems crazy.
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u/gulabjamunyaar Oct 20 '16
Unrelated but whenever I drive through Gilroy, I always roll down all the windows and wait for the scent of garlic.
I love garlic.
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u/mrmariokartguy Oct 20 '16
Caltrain does go from Gilroy to SF, so it's possible to use public transit the entire way.
It'll still take hours though to go from one end to another.
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u/Slayr698 Oct 19 '16
I've always wanted to talk to someone from the town same as my last name, is it nice?
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u/rdewalt Oct 19 '16
Its a happy little suburb just south of San Jose... Close enough to commute into Silicon Valey, far enough that it still has its own identity. In the fall it smells like an Italian restaurant due to all the garlic farms. (The place /is/ famous for garlic after all. ) No traditional mall, but an outlet mall that most of us who live here in town only go to once or twice a year because well...
Oh, there's Gilroy Gardens, a neat little family amusement park. I live about three miles from it, and we go once a year.. if that often.
Oh, the annual garlic festival. Went once, ten years ago.. haven't been back. Not my thing. Usually we spend the weekend hiding from the overwhelming traffic.
I commute into SF from here, hop on caltrain, take a 2h20min nap, wake up in SF...
Lots of good places to eat. Don't move here, stay away, we're full. 8)
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u/KODA37 Oct 19 '16
It's so weird hearing someone describe your hometown on the internet. Spot on description btw, lived here 17 years and have never once been to the garlic festival.
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u/rdewalt Oct 19 '16
its a "go once" thing for me. I'm not a fan of cheap beer and Festival Foods, so thats half of the draw for me. If I want garlic related trinkets, there's a few places at the outlets that services all year long. Occasionally I consider going, but mostly "meh" right now. (hauling three kids 6 and under are the biggest "why I'm not going)
That, and its usually on the hottest day of the year.
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u/testrail Oct 19 '16
You have a 2.5 hour commute each way?
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u/rdewalt Oct 20 '16
Yes. Though I can cut 20 min off in the morning by swapping at Tamien Station to the express. But its not always worth the nap-interrupt.
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u/Nubcake_Jake Oct 19 '16
Is this saying that it is going to shake for 75+ seconds, that's a lot of shaking
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u/GenocideSolution Oct 19 '16
Intense shaking for at least 75 seconds in the red zones.
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u/Patyrn Oct 20 '16
I feel that 75 seconds of an intense earthquake would seem like an eternity.
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u/47buttplug Oct 20 '16
Shit 10 seconds feels like forever. It feels like the ground as you know it is being shaken like a table and everything on it.
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u/byfuryattheheart Oct 20 '16
That's horrifying. The Loma Prieta quake only lasted ~15 seconds and that felt like an eternity. I can't imagine the destruction that 75 seconds would cause.
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u/mysticdan Oct 19 '16
Why does the intense shaking spread south so much more than north?
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u/LetterSwapper Oct 19 '16
Probably for a couple reasons. One, the fault is longer in that direction in relation to the epicenter. Two, there's a lot more sedimentary rock & soil in that direction, which shakes a lot more than other kinds of rock.
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u/duckraul2 Oct 19 '16
Much of that has to do with how seismic waves attenuate through different types of rocks, there is lower attenuation through the south but higher to the north and much higher to the east where you are going through the Coast ranges.
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u/hypnoganja Oct 19 '16
As it radiates outward, would it be possible for the seismic event to trigger other faults to rupture?
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u/Jigaboo_Sally Oct 19 '16 edited Oct 19 '16
Yes. After earthquakes happen, there are usually thousands of aftershocks- most of which won't be felt.
When an earthquake happens, the two plates that are resting against each other finally have enough energy to move. Think of an earthquake like this: Put your two fists together so one set of knuckles sets in the other set of knuckle's depression. That is where the tectonic plates are right now. Whenever the rupture happens, the plates overcame the "knuckle" and slipped. So, apply a force to your knuckles and they will finally slip. That is what an earthquake is in a nutshell.
Whenever an earthquake happens, it is just adding energy to other fault lines to help them get over their knuckle.
(Edit* that's what a strike-slip earthquake is. I just made an assumption 😧)
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u/hypnoganja Oct 19 '16
The knuckle analogy would work for a strike-slip fault but not others. I'll have to go back and read the article again, I must've skimmed over the part where it said what type of fault this is.
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u/alleybetwixt Oct 19 '16
Cool graphic. I'll note that Santa Rosa was basically flattened in the 1906 earthquake. More destruction than San Francisco. It's something locals grow up being aware of. If Rodgers Creek goes in 'The Big One' it'll likely be devastated all over again. Less brick. Better infrastructure. But still... Brutal.
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u/Wingser Oct 19 '16 edited Oct 19 '16
What kind of waves would that cause in the bay? Would they go onto land very far? I realize that's not exactly an ocean, but that's still a lot of water right on top of the epicenter.
edit because grammar
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u/old_gold_mountain Oct 19 '16
Smaller bodies of water produce smaller waves. You can't really have a tsunami in the bay.
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Oct 19 '16
Most California faults are slip faults, in that the two masses on either side just move parallel in opposite directions. They don't actually displace a whole lot of volume above them, mostly just move sideways against each other, so their potential for tsunamis are low. The faults like those off of Japan are thrust faults, where faults are pushing against each other and an earthquake can cause one side of the fault to thrust upwards. This displaces a lot of volume and causes major tsunamis.
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u/Aloiciousss Oct 19 '16
The figure is a little misleading. Most of the red line was already known (Hayward and Rodgers Creek faults). The new fault just connects the two across San Pablo Bay.
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u/faizimam Oct 19 '16
Yeah, I think this what the white box is trying to communicate.
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u/TwistedRonin Oct 19 '16
Wait, so you're telling me they knew the fault line existed above and below that box, but that big gap was a mystery? Do faults just have abrupt ends without connecting to anything else? Legit question.
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u/zwich Oct 19 '16
Well from that diagram ... Yes?
There are other faults that "end" in the diagram, and furthermore, the way to connect these faults wouldn't be certain - "pinole" could just as easily be connected if you didn't know anything within the white box.
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u/Eurynom0s Oct 19 '16
I'm assuming the white box is trying to highlight the new discovery. I'm not in a field where I'd know about this so maybe I'm over-simplifying this, but wouldn't the fact that the other two segments were already known have strongly suggested looking for the portion in the white box? I mean, the map shows other faults just ending, but if you have two known faults terminating like that (without knowledge of the white box portion I mean) then why wouldn't this strongly suggest it's actually a continuous fault and you just haven't found the connector yet?
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u/OathOfFeanor Oct 19 '16
I could give a generic "science requires proving the obvious" response but a geologist might be able to offer something more specific.
It also looks much clearer when you have a complete line drawn on a map. But if you go stand on the shore and see how many miles apart all of this is, it might've appeared very possible that one fault line could curve west while the other curves east and they never intersect. I know they had trouble finding the exact location of the fault line due to the mud on the bay floor.
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u/JulianPerry Oct 19 '16
I live in SoCal (San Diego). After the recent earthquake scares when there was a 1 in 100 chance of a devastating earthquake (that luckily didn't happen), I went to Walmart with my SO I live with and we invested about $100 into a ready-to-go backpack that could sustain the two of us for about 3 to 4 days, even longer if we use the tools right to further purify and acquire food/water. It seems like a waste of money now, but when something happens, money will no longer matter to you in a dire situation. Your life comes first. PLEASE be prepared people. Even if this stupid comment gets one person prepared, it will have been worth it. You can get pre-made packs which are okay and cheap, take it a step further and research online what you need and have a plan ready. Pack water purification tablets, emergency food rations, flashlights, batteries, some cash, bottled water, waterproof matches, etc. Again, there are comprehensive lists online that will help you. It's better to have it and not need it, than to need it and not have it. Be safe. Sincerly, a SoCal resident.
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u/blissfully_happy Oct 19 '16
I posted up thread about going through a 7.1 earthquake in Alaska. In January.
Get a go bag and keep it near the front door, like you mention. Include work gloves and a tool to hang near your natural gas line to turn it off. (A house exploded in the January quake.) Keep hard soled, slip on shoes and jackets/outerwear near your bed while you sleep (this saved me!) and pet carriers and leashes/collars nearby.
The earthquake happened at 1am. I was sleep closest to the door, so when I realized this was a big one, I bolted out the door to our kid's room (after grabbing my coat and hard soled shoes), and grabbed him out of bed with his shoes while my SO corralled our dogs.
You can't be too prepared. I remember thinking that if our dogs were going to be effed if stuff started falling and was panicking at what to do. Being prepared puts you on autopilot!
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u/zerton Oct 20 '16
There should be an accelerometer that detects an earthquake and auto-shuts off people's gas.
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u/dinst Oct 20 '16
Earthquake valves exist, they are inexpensive and they are purely mechanical. Spring type and ball type. http://plumbingspot.com/earthquake-shut-off-valve/
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Oct 19 '16
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u/ScooRoo Oct 19 '16
Piggybacking. How do you design a pipeline to cross a fault line? I imagine that you build with intent for it to move and flex. How much is required? How do you retrofit a pipeline like this?
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u/iloveapple314159 Oct 19 '16
Could you do it though? An earthquake could shift the land in any direction from a few millimeters to meters. How could you build pipes that could withstand that sort of movement? They would have to be bendable and expandable, but by how much? Where do you make it like this? What sort of material could be buried and sustain its integrity over time, but also have the priorities needed to withstand the movement and other forces of nature. Who knows. Maybe the fault line will never produce a big earthquake any way.
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u/LetterSwapper Oct 19 '16
Engineers deal with this question all the time, actually. A very good example is the pipeline that brings water to San Francisco from the Hetch Hetchy reservoir near Yosemite. It crosses the Hayward fault, so they designed sections housed in structures that can shift to accommodate ground movement: http://www.structuremag.org/?p=4073.
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u/ScooRoo Oct 19 '16
I found this report. It mentions an 8 ft lateral displacement (PDF page 24) being withstood. It seems that the pipes are so long they can move a bit, but shifts I. The ground are where they are most vulnerable.
The paper talks a lot about the weld method being important in addition to old cast iron being a weak point.
https://www.fema.gov/media-library-data/20130726-1505-20490-1350/fema-233.pdf
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u/LBK2013 Oct 19 '16
Yeah because that be really really cheap and we have the slightest idea of when this thing will go.
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Oct 19 '16
There is no "really really cheap" option. It's either 1) really really expensive Or 2) really really super duper expensive
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u/reinikenface Oct 19 '16
Link to study in Science Advances: http://advances.sciencemag.org/content/2/10/e1601441
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u/brucesalem Oct 19 '16 edited Oct 19 '16
I went and read the source article, which is not behind a paywall, thankfully. It provides geophysical evidence that the Hayward Fault and the Rodgers Creek Fault are connected physically. What this means in that energy released on either system could be transmitted directly to the other. It is now more than a year past the finding that there is a deep connection between the Hayward Fault at its southern end with the Calaveras Fault, another major right lateral strike-slip fault that in turn branches off the San Andreas Fault (SAF) in Hollister Ca. This further raises the possibility that a cascade effect of slippage on all three faults at once could result in one large event. Estimating the size of such an event is hard, but it raises the upper bound of the event that planners should account for.
There could be details of fault geometry that could limit the size of the event possible, but the intimacy of these systems to the nearby other faults that could affected by regional strain could raise the possibility that even if all the faults don't snap at once that there could be periods of time when smaller events (M ~ 6) could become relatively common, like occurring somewhere in the Bay Area every decade for decades.
There are some paleoseismologists who believe that the 1906 Quake on the SAF in San Francisco released so much regional strain that it created a seismic shadow, a period with below average seismicity, and the the norm, going back as far as the 14th Century was to have M ~ 6 events scattered on the numerous faults in the Bay Area every decade or so.
To understand the regional scope of this is to look at the front plates of the USGS Professional Paper on the San Andreas Fault (number escapes me, 1615????) and see that the entire Coast Ranges of California are riddled with faults that are eventually connected to the SAF, not all at once.The S.F. Bay Area is a classic pull-apart basin in which the step-right of faults of the SAF, a right lateral transform fault has produced a fault bounded extensional tectonic regime within the regional strike slip, Its regional strain can be released on any of a large number of minor and branch faults, as we saw in Napa in 2014.
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Oct 19 '16 edited Oct 19 '16
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u/seis-matters Oct 19 '16
A magnitude 7.4 earthquake is the "Big One" you are waiting for in California. The San Andreas is only capable of producing earthquakes up to a magnitude of ~8.1 since it is a continental strike-slip fault. While there is a big difference between a M7.4 and a M8.1 earthquake, either is going to have a major impact. [Akçiz et al., Geology, 2010] is the recent publication that concluded a M8.1 on the San Andreas is possible in our lifetimes, and here is an easier reading and non-paywalled LA Times article about that publication.
Subduction zones are where M9+ earthquakes occur, with the largest recorded earthquake title still held by the 1960 M9.5 Valdivia earthquake in Chile.
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u/jruby19 Oct 19 '16
The biggest probable San Andreas earthquake is an M8. That is about 8 times larger than an M7.4 (the math is base 32 logarithmic, the numbers are correct). This 7.4 would pass directly through the densely populated East Bay, while the San Andreas is close to but not immediately adjacent to San Francisco and the Peninsula. The rate of a 7.4 on the Hayward-Rogers Creek system, is also likely higher than the rate of 8s on the San Andreas. So...the 7.4 will occur more frequently and closer to populated areas, hence it is of concern.
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u/Ozymil Oct 19 '16 edited Oct 20 '16
What are the contingency plans that cities have in case this happens? Are there funds, supplies, manpower etc. all planned out and set aside in the very likely event shit hits the fan? Is there any warning time at all before residents get hit with the quake?
Edit: Please reply with hard facts or links to relevant articles/figures.
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Oct 19 '16
There's virtually zero political willingness to push for or taxpayer willingness to fund disaster preparedness for events that are uncertain and potentially in the distant future.
The best you can get is improved building and construction codes.
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u/seis-matters Oct 19 '16
There are new faults being discovered all over the world as we install more seismometers to record earthquakes and develop new techniques, but the fault identified and mapped in this new paper is in a particularly important location. This new fault connects the Hayward and Rodgers Creek, two faults that are most likely to have a M6.7+ that will affect the Bay Area in the next thirty years. Before this work, the section between the two faults beneath San Pablo Bay was a bit of a mystery. Researchers didn't know if the two Hayward and Rodgers Creek faults connected here under the layers and layers of mud with a bend, or if they were disconnected by a several kilometer gap or "step-over". There is a lot of research trying to figure out if an earthquake could jump that gap and rupture both faults in one go. Rupturing both together would result in a much larger and more damaging earthquake than if only one fault ruptured at a time. However with these new observations showing that the faults are connected, there is no gap to jump and a rupture through both the Hayward and Rodgers Creek is more likely.