11:32 am PDT. Thanks everyone for the good questions. I had fun. Signing off. Lucy

Hi, everyone! I’m Dr. Lucy Jones, USGS Seismologist. With the recent movie release of San Andreas, I thought it would be a perfect time to separate the fact from the fiction when it comes to the San Andreas fault system. I'll be on at 1:30pm (Eastern)/10:30am (Pacific).

We also have all of our earthquake information and data available at http://earthquake.usgs.gov/

I just tweeted the IAmA from @DrLucyJones on Twitter: https://twitter.com/DrLucyJones/status/605421046573850624

Comments: 167 • Responses: 28  • Date: 

geocatherder41 karma

What is the latest thinking on the possibility of a big earthquake on one fault triggering a big earthquake on another wound-up fault? For example, can a San Andreas fault quake in the San Francisco Bay Area trigger a Hayward fault quake?

Dr-LucyJones52 karma

Yes, earthquake triggering is very realistic. A Hayward fault earthquake after a San Andreas quake would just be considered an aftershock - like the Big Bear aftershock to the Landers earthquake.

We also see triggered earthquakes at greater distances where we don't use the word "aftershock" but they are still related. In the day after the great 1906 earthquake that devastated San Francisco, we saw a M6.0 in Imperial County and a M5 in Santa Monica Bay

dbxwr40 karma

What is your opinion of (building) a hi-speed rail line that crosses the S.A. faultline ?

Dr-LucyJones76 karma

The Japanese have shown that you can safely operate hi speed rail with earthquakes if you have earthquake early warning systems. No trains derailed in the 2011 M9 because no trains were moving when the strong shaking got to them.

Xzadows32 karma

I notice that reports do not use the term "Richter Scale" anymore and the term "magnitude" is used in the same context instead. What is the difference between the two if there is?

Dr-LucyJones53 karma

"Richter Scale" used a very particular type of seismogram. "Magnitude" can be one of many different ways to determine the innate size of the earthquake. The most reliable now is "Moment magnitude" that processes the complete seismogram for the best picture of the total energy.

Neither of these is what you feel in an earthquake. That is described by "Intensity", usually the Modified Mercalli Intensity scale. . Because the shaking varies from place to place in a given earthquake, the intensity does to

coonlife26 karma

What should I have in my earthquake kit? And what should my course of action be in the event of a devastating earthquake in LA?

Dr-LucyJones45 karma

A good discussion of how to be ready for an earthquake is at http://earthquakecountry.org/sevensteps/

But remember that you can and should do more than be ready to pick up the pieces. We can prevent the pieces from coming down in the first place. Have you had your home's foundation inspected? Have you secured bookcases?

jkljkl12425 karma

Could we possibly set off a big quake by either

  1. A nuke detonated along the faultline, James Bond style?
  2. Injection of deep liquids a la fracking?

I'm not Al Qaeda, I swear.

Dr-LucyJones35 karma

Nuke no. We set off huge nukes in Nevada during testing and the biggest earthquake we ever set off was a M3.7

Injection, maybe. The increased pore pressure reduces the effective friction on the fault. The largest induced earthquake we know about is a M6.5 at a dam in Kazakhstan.

jdbranded23 karma

What's the biggest possible earthquake the San Andreas fault could produce? I can't remember where, but I read that even if the entire fault ruptures, it wouldn't be bigger than 8.0 or so.

Dr-LucyJones46 karma

If the whole southern section goes in one earthquake, that would 8.2 to 8.3

silkyhankering11 karma

Can you specify what you mean by 'goes'?

Dr-LucyJones21 karma

An earthquake begins at an epicenter but happens over a whole surface. The rupture moves from the epicenter up the fault at about 2 miles/sec. Where it stops determines the magnitude

tommyburger23 karma

Hi Dr. Jones! I'm a Los Angeles native, been through the Northridge quake, etc. I think you're awesome.

Question: what are the biggest myths the public has regarding earthquakes?

Dr-LucyJones52 karma

"California falling into the ocean" - the ocean is not a hole. It is land with a lower elevation "We have good building codes so we must have good buildings". Building codes aren't retroactive so your building is as good as the building code in place when it was built. Also, our building codes are life-safety only - make sure you can crawl out alive

JSquiddy1018 karma

Hi Dr. Jones. My question involves the amplification in the LA Basin. If I understand the science correctly, does that mean that areas like the Hollywood Hills (which are built on solid rock and not in the basin) would experience less shaking than an area like lets say West Hollywood or Beverly Hills? Or would the shaking intensity be similar? How much does the ground that an area is built on play into that shaking?


Dr-LucyJones25 karma

For the same earthquake wave coming in, the Hollywood Hills will have less shaking than a site in the flats. We have made a map of what the amplification factor is, based on type of sediment and thickness of sediment. http://www.scec.org/phase3/amplificationmap.html Downtown LA has about a factor of 5 amplification. Beverly Hills is about 3.

two_off17 karma

What's your review of the movie?

Were you able to suspend your knowledge about the topic and focus on the movie or were you always taken out of it by the things they did wrong?

Dr-LucyJones29 karma

I actually did a review of San Andreas for the Hollywood Reporter. See http://www.hollywoodreporter.com/news/a-seismologist-reviews-san-andreas-798800

I enjoyed it but didn't worry about the very bad seismology

Dr-LucyJones12 karma

I also live tweeted the premiere https://twitter.com/DrLucyJones

my9r1desshotgun16 karma

do you think it is harmful to the understanding of earthquakes that the SAF is portrayed as a subduction zone in the film?

Dr-LucyJones25 karma

Only if people believe it. I think it is getting people talking and asking so maybe people will now hunt out information. If you want to know about tsunamis in California, we did a scenario of one of the worst possible tsunamis. For California, that is coming from Alaska.http://www.usgs.gov/natural_hazards/safrr/projects/tsunamiscenario.asp

The damage in all within 1 mile of the coast

mama_says15 karma

What can be done to convince more people to get covered by earthquake insurance?

I live in the Bay Area and I've been asking around my friends if they have policies just out of curiosity. Wow. The complancency, the fatalism, and the just plain "I dunno"s are amazing.

Dr-LucyJones25 karma

We have to see earthquakes as the threat to our pocketbooks rather than a threat to our lives. You are more likely to die in a auto accident than an earthquake. Our estimate of a San Andreas earthquake in southern California is more than $200 billion in losses. The USGS works with the California Earthquake Authority to understand the rate of earthquakes so they can set reasonable rates. http://www.usgs.gov/newsroom/article.asp?ID=4146#.VWyZCFzBzRY

MalevolentCat18 karma

I'd bet that if an 8.0 earthquake hit, the insurance company would file bankruptcy and go under without providing you support. The damages they would have to pay would far outweigh any possible future profit and there would be no point in them even trying to stay open. Their bets are on there NOT being a major earthquake, and if there is, their execs have already made enough money to live comfortably. It might be helpful with lower-strength or more localized earthquakes, though. I personally think earthquake insurance is a bad investment for most people.

Source: see victims of the Hurricane Katrina who had hurricane insurance.

Dr-LucyJones38 karma

So few people have earthquake insurance at this point that the insurance companies won't have a problem paying up. The California Earthquake Authority is a public entity, not a private insurance company, & always buys reinsurance at whatever level they need to cover all claims.

efects14 karma

do you live in california? if so, are you doing anything different than the standard advice to prepare for the so called, big one?

Dr-LucyJones43 karma

I have lived in California my whole life with the exception of time at college and grad school. I focus on making sure that all preventable damage is prevented. When we buy a house, we get a foundation specialist to inspect the foundation and strengthen it if possible. We hook down our bookcases and TVs, big computers, etc. My grandmother's china is stored in protected cases on bottom shelves. We don't have glass framed pictures in bedrooms or halls. The earthquake is inevitable but the disaster is not.

Rabbit_3814 karma

If there is a major earthquake along the San Andreas fault, will it result in the entire faultline rupturing and causing severe damage right along the line?

Dr-LucyJones24 karma

The length of the fault that moves in an earthquake determines the magnitude. We think that sometimes only part of the fault will go and sometimes the whole southern section. The middle part of the fault creeps in small earthquakes and we think we won't have a big earthquake through that. The damage will be heavy near the fault and die off with distance. But basins (like LA) will see amplification

MedicUp13 karma

Dr. Jones, thanks for doing this AMA.

When California's Earthquake Early Warning System finally gets rolled out for public release- as a seismologist - what magnitude/intensity of earthquake would you want for it to alert you to? I would imagine a seismologist would want to be alerted to everything compared the average citizen that is averse to non-significant shaking.

(Maybe another way of phrasing the question: what magnitude/intensity of earthquake in the State gets you particularly excited/interested)?

Dr-LucyJones20 karma

I have the prototype EEW on my computer and have it alert for every 2.5 - but that's when I am at my desk and working, not for instance, when I am asleep. I think most citizens would want to know whenever they will have obvious shaking - Intensity III or IV. The EEW message will reassure you that this is NOT going to grow into a big earthquake

WayneWilco11 karma

Are you familiar with the method called "Operational Earthquake Forecasting" that Dr. Tom Jordan is involved with? Based on the idea that probabilities fluctuate over months and weeks. Do you think that shorter term forecasting is something that should be pursued?

Dr-LucyJones11 karma

Operational Earthquake Forecasting is not a "method" per se. It is an operational approach to routinely use the various methods we have for calculating short term changes in probability in a routine manner for use by the public. Tom and I wrote the first editorial about OEF in Seismological Research Letters. http://srl.geoscienceworld.org/content/81/4/571.extract The biggest changes are the hours right after a big earthquake. My early research was on how to calculate the probabilities and was used for the State of California to issue advisories. OEF is trying to do the same thing automatically.

alpinevx11 karma

How possible is the scenario of an earthquake severing the southern part of California into the ocean/abyss? Obviously this is a bit of an apocalyptic fantasy, but it seems like a strong enough earthquake along the San Andreas would actually make this come true.

Dr-LucyJones41 karma

The San Andreas does not open up!. During an earthquake the western side moves north. If it could open, there would be no friction and there would be no earhtquake

Donghanger9 karma

Do you think buildings that arent in high earthquake zones should still be built to earthquake proof standards like those in SoCal? Just in case?

Dr-LucyJones31 karma

You make the mistake of thinking that buildings in California are “earthquake proof.” In fact, the California standard is only “life-safety” – make sure you can crawl out alive. This is going to make it very difficult for our economy to recover after an earthquake and is a reason that Mayor Garcetti of Los Angeles asked for http://lamayor.org/earthquake
In other regions, I think that life-safety is a good standard. So I’d like to see not active areas go up to the life-safety standard and California to go above it.

CoffeeHamster9 karma

How big would the earthquake have to be for people to, as the trailer put it, "feel [it] on the east coast?"

Dr-LucyJones36 karma

Impossible big

lp4ever558 karma

Hey! What other geology "related" movies do you like? Any "hidden gems" that I might not know about?

Dr-LucyJones12 karma

The original Earthquake movie in 1973 had an advisor from Caltech and the seismology is not bad.

baseball5008 karma

If a quake struck off coast of Los Angeles, how large a tsunami could we see? I'm particularly curious whether there is high-ground in the area of Santa Monica/Venice/Marina del Ray that could be "high enough" to be safe?

Dr-LucyJones9 karma

There is plenty of territory that is high enough. The State tsunami hazard maps http://www.conservation.ca.gov/cgs/geologic_hazards/Tsunami/Inundation_Maps/Pages/Statewide_Maps.aspx

are the basis of the posted signs you see. Those maps include possible offshore faults. Luckily, southern and central California do not have a subduction zone - the only type of fault that moves enough water to create a very big tsunami

Bronloneus5 karma

My 5th grade son loved San Andreas!

Do you know of any good mnemonic devices for remembering the difference between p-waves and s-waves? I teach 4th grade science.

Thanks for doing this AMA.

Dr-LucyJones11 karma

"P-wave" literally means primary wave and "S-waves" are secondary waves. The P wave comes first

WayneWilco4 karma

Hi Lucy! I have heard you say that a large earthquake could just be a small earthquake that grows without stopping. Does this mean that there has not been a small earthquake (even magnitudes <2) on the locked portions on the San Andreas itself in modern times?

Dr-LucyJones13 karma

The southern San Andreas does not have small earthquakes. There are small earthquakes around it but not on it. We think that the San Andreas has really big earthquakes because it is so weak, it cannot stop a little rupture from getting bigger.

JSquiddy103 karma

When we hear about a fault going, what is the importance of the direction of the rupture? For the handful of Baldwin Hills small quakes we've been having, I've been in the same place for most of them, and one gave my place a nice jolt, while the other (almost the same magnitude) was barely noticeable. If the SAF goes north to south how different would that be for LA County and SoCal as a whole?

Dr-LucyJones4 karma

Direction of rupture only matters on large earthquakes. The shaking is stronger when the rupture is moving towards you. In the small earthquakes, the difference is either the size (a M3.8 is actually many times stronger than a M3.3) or the radiation patter - the shaking varies with your orientation to the fault that produces it.

theacidbull3 karma

What's your opinion on the US Geological Survey's report on earthquakes being caused by oil and gas drilling or more specifically fracking? http://www.theguardian.com/world/2015/apr/24/earthquakes-fracking-drilling-us-geological-survey

Dr-LucyJones6 karma

The report does not show that earthquakes have been caused by fracking. The report confirms the triggering of earthquakes by increasing the pressure in ground water at the depth that earthquakes occur (below about 2 miles in the earth). We see induced earthquakes where they dispose of wastewater produced during the fracking at depth, or at geothermal power plants

NaturalisticAsHell2 karma

Fracking causes earthquakes. True or False?

Dr-LucyJones7 karma

The report does not show that earthquakes have been caused by fracking. The report confirms the triggering of earthquakes by increasing the pressure in ground water at the depth that earthquakes occur (below about 2 miles in the earth). We see induced earthquakes where they dispose of wastewater produced during the fracking at depth, or at geothermal power plants