Fault off San Diego, Orange, Los Angeles counties could produce 7.3 earthquake

UNIVERSITY OF CALIFORNIA – SAN DIEGO

SCEC Community Fault Model. This map shows the 3-dimensional structure of major faults beneath Southern California. Vertical faults such as the San Andreas (yellow band from top left to bottom right) are shown as a thin strip. Faults that are at an angle to the surface are shown as wider ribbons of color. The nearest fault to you might be a few miles beneath your home. Areas that seem to have few faults can still experience strong shaking from earthquakes on unmapped faults or from large earthquakes on distant faults.

Fault system off San Diego, Orange, Los Angeles counties could produce magnitude 7.3 quake
Study finds rupture of offshore Newport-Inglewood/Rose Canyon fault is possible – fault previously produced a 6.4-magnitude quake in Long Beach, Calif. that killed 115 people in 1933

A fault system that runs from San Diego to Los Angeles is capable of producing up to magnitude 7.3 earthquakes if the offshore segments rupture and a 7.4 if the southern onshore segment also ruptures, according to an analysis led by Scripps Institution of Oceanography at the University of California San Diego.

The Newport-Inglewood and Rose Canyon faults had been considered separate systems but the study shows that they are actually one continuous fault system running from San Diego Bay to Seal Beach in Orange County, then on land through the Los Angeles basin.

“This system is mostly offshore but never more than four miles from the San Diego, Orange County, and Los Angeles County coast,” said study lead author Valerie Sahakian, who performed the work during her doctorate at Scripps and is now a postdoctoral fellow with the U.S. Geological Survey. “Even if you have a high 5- or low 6-magnitude earthquake, it can still have a major impact on those regions which are some of the most densely populated in California.”

The study, “Seismic constraints on the architecture of the Newport-Inglewood/Rose Canyon fault: Implications for the length and magnitude of future earthquake ruptures,” appears in the American Geophysical Union’s Journal of Geophysical Research.

The researchers processed data from previous seismic surveys and supplemented it with high-resolution bathymetric data gathered offshore by Scripps researchers between 2006 and 2009 and seismic surveys conducted aboard former Scripps research vessels New Horizon and Melville in 2013. The disparate data have different resolution scales and depth of penetration providing a “nested survey” of the region. This nested approach allowed the scientists to define the fault architecture at an unprecedented scale and thus to create magnitude estimates with more certainty.

In 2013, Scripps research vessel New Horizon towed a hydrophone array to map the bathymetry of the Newport-Inglewood/Rose Canyon fault zone.
CREDIT
Scripps Institution of Oceanography at UC San Diego

They identified four segments of the strike-slip fault that are broken up by what geoscientists call stepovers, points where the fault is horizontally offset. Scientists generally consider stepovers wider than three kilometers more likely to inhibit ruptures along entire faults and instead contain them to individual segments – creating smaller earthquakes. Because the stepovers in the Newport-Inglewood/Rose Canyon (NIRC) fault are two kilometers wide or less, the Scripps-led team considers a rupture of all the offshore segments is possible, said study co-author Scripps geologist and geophysicist Neal Driscoll.

The team used two estimation methods to derive the maximum potential a rupture of the entire fault, including one onshore and offshore portions. Both methods yielded estimates between magnitude 6.7 and magnitude 7.3 to 7.4.

The fault system most famously hosted a 6.4-magnitude quake in Long Beach, Calif. that killed 115 people in 1933. Researchers have found evidence of earlier earthquakes of indeterminate size on onshore portions of the fault, finding that at the northern end of the fault system, there have been between three and five ruptures in the last 11,000 years. At the southern end, there is evidence of a quake that took place roughly 400 years ago and little significant activity for 5,000 years before that.

Driscoll has recently collected long sediment cores along the offshore portion of the fault to date previous ruptures along the offshore segments, but the work was not part of this study.

In addition to Sahakian and Driscoll, study authors include Jayne Bormann, Graham Kent, and Steve Wesnousky of the Nevada Seismological Laboratory at the University of Nevada, Reno, and Alistair Harding of Scripps. Southern California Edison funded the research at the direction of the California Energy Commission and the California Public Utilities Commission.

“Further study is warranted to improve the current understanding of hazard and potential ground shaking posed to urban coastal areas from Tijuana to Los Angeles from the NIRC fault,” the study concludes.

###

Full paper, open source: http://onlinelibrary.wiley.com/doi/10.1002/2016JB013467/epdf

Advertisements

101 thoughts on “Fault off San Diego, Orange, Los Angeles counties could produce 7.3 earthquake

    • Hmmm. Now, if only we could find a way of completely removing this problem through, say, increased taxation. Then we could revoke the citizens of Earth’s carbon sintax. Win, win. What’s not to like?

      The doobie always gets passed to the left.

  1. There is evidence that warming of the crust leads to earthquakes and volcanos as shown by the increase in volcanic activity after we enter the inter-glacial period and the modulation of mid-oceanic crust formation by the ice-age cycle.
    http://scottishsceptic.co.uk/2017/02/03/the-caterpillar-effect-now-with-second-confirmation-it-must-be-rock-solid-science/

    It is therefore possible to argue that global warming causes ice-ages and if this fault is part of the general westward moving zone on the west coast of America then any earthquake here could be attributed to global warming – even though the relevant global warming took place ~10kyrs ago.

    • Hey man. That must be some good $#;+ you are smoking. Why don’t you pass it around.

      • I don’t see why that 7.3 couldn’t become an 8.3 with a simple doubling of atmospheric CO2.

        ($200K buys a complete study including a state-of-the-art hybrid geologic/climate model. Results guaranteed ;)

      • The physics is simple, when rock heats up it expands. It is therefore simple physics that the crust will have expanded as a result of the ice-age warming and we can work out that that effect reaches several kilometers down into the crust. As the article I link to above shows, there is evidence of increased volcanic activity as we warm up and there are changes in the formation of the mid-oceanic ridge.

        So the Caterpillar effect is well supported by the science and evidence.

        But what would be very difficult to sustain is that warming since the little ice-age will have much effect as that heat has only penetrated a few 10s of meters. – however no doubt we’ll sooner or later hear some alarmist suggest it has an effect.

    • I think the correlation is between post-glacial crustal rebound, rather than atmospheric warming of the crust.

  2. “never more than four miles” from the coast. Is that close enough that there wouldn’t be a tsunami?

    • Wrong sense of motion on the fault – strike -slip will not produce vertical movements needed to generate a tsunami

      • Wrong sense of motion on the fault – strike -slip will not produce vertical movements needed to generate a tsunami

        Good logic, but … the Rose Canyon section of the fault running from just East of La Jolla, South to the I5-I8 junction has a visibly downtilted fault delineated block on its West side. As you drive North on I5 from Pacific Beach, Interstate 5 runs right along the (previously assumed to be inactive) Rose Canyon Fault. The strata on the East (Clairemont Mesa) side are visibly flat lying. Those on the West (Mt Soledad) side dip visibly to the South. I used to drive that most every day. Never really believed that the fault was inactive. Still don’t believe it.

      • RE: Don K

        From the article :
        “They identified four segments of the strike-slip fault”
        …. Having not mapped the geology myself, I took them at their word. Perhaps it is an oblique compressional fault (neither fully dip slip or strike slip), thus giving the authors to classify it as strike slip ?
        Oblique slip faults are not unheard of in SoCal based on focal mechanisms.

      • Jeff. I wasn’t really criticizing. And you’re surely correct for most places other than Southern California and (probably) Japan. Even there, you’re likely mostly correct. Furthermore, much of the Southern California coastline has decent sized sea cliffs between the ocean and the population which should limit tsunami damage even more. The problem is that the region adjacent to the San Andreas is a jumble of often poorly mapped faults intersecting other faults and I don’t see how earthquake risk there can be projected with all that much confidence. Not a region where, for example, pumping fracking fluids into the ground is likely to be a good idea. Come the next quake, you’ll be sued whether your fluids had anything to do with the damage or not.

        Here’s a link to a — somewhat alarmist IMHO but still concerning — article on the offshore faults in the region. https://news.agu.org/press-release/little-known-quake-tsunami-hazards-lurk-offshore-of-southern-california/

      • “Furthermore, much of the Southern California coastline has decent sized sea cliffs between the ocean and the population which should limit tsunami damage even more.”

        There are no cliffs at Ventura but there are a lot of folk living just above sea level.

    • Slip/strike faults slide horizontally, thus they don’t displace as much water as do subduction faults. Tsunamis aren’t out of the question, but the damage should be less.

      • correct, and agreed. however there are places where strike-slip faults near very steep underwater landscape can trigger large scale slumping/landslides. these are strong tsunami generators.

  3. Could, might, maybe . . . . Call me when you get to the point where you can definitely say “will” and “when.” Up to then, I can make the same predictions you can.

    • When they get to “will” and “when,” it will be too late to do anything but run outside and pray that a building doesn’t fall on you.

    • When dealing with earthquakes, probabilities is all you got.
      For example, when an earthquake starts, how much of the fault slips is a big factor in determining how strong the earthquake ends up being.
      In this situation, the mechanism by which faults that aren’t directly connected but are close to each other are not precisely understood. However it is known through observation that the closer to faults are too each other the more likely (but not guaranteed) it is that a rupture that starts on one fault could transfer to and continue on, another.
      The knowledge that the end points of these two fault systems are closer together than previously thought increases the chance that they will act as a single fault if there is a big quake.
      That is useful knowledge because it gives building designers and emergency preparation teams better information with which to do their jobs.

    • When it comes to earthquakes, probabilities is all you got. It’s impossible to get perfect information on how much strain has built up. Nor is it possible to get perfect information on what the condition of the rocks below our feet are in.

  4. I realize that it’s important to study and map and understand these faults, but how useful (in the rudimentary sense of the word) is this information. We really can’t predict earthquakes with any degree of certainty and certainly not certainly enough to be able to take any action (e.g. “evacuate”). I’m not pooh-poohing this research but I have to wonder.

      • This isn’t really about accurately predicting the next earthquake. It is about sounding authoritative enough to get the next grant.

    • If we know that a bigger earthquake is possible, then the designers of buildings will know that they need to build stronger buildings and the disaster response teams will know that the possibility of greater damage exists and their plans need to adjust.

      • PS: It’s nice to see scientists admit that there are limits too their knowledge for a change.
        As opposed to claiming that we know the temperature of the earth to within a thousandth of a degree.

      • That is quite right. See New Zealand for earthquake strengthening of buildings. Some older historic buildings are demolished because there will be big quakes in the future. and others are closed until strengthening can be accomplished. Even more modern buildings have to be brought up to higher standards of strengthening than when they were built. So the predictions in California will be taken to heart by planners and builders.

    • scientist have been constantly reevaluating faults in Californian when new information or scientific understandings develop. The state in turn constantly adjusts or modifies building codes to account for the new knowledge. In the last 20 years California has modified or replaced most freeway overpasses and bridges because we know know the old earthquake codes were deficient. The most recent big bridge to repaced is the East section of the bay bridge. It was badly damaged in 1989 and repaired but after evaluating most retrofit options they decided to replace it. While there are a lot of unsubstantiated claims of poor or faulty construction most independent engineer consider it to far safer than the old bridge. Additionally in the San Francisco bay area about 12 dames have also been modified due to the improved understanding of earthquake faults in the area. Some of these dams also received spillway upgrades to account for our better understanding of 100 year flood events such as the 1866 flood much of central California. Orville dam was not affected by earthquake code changes because it is not near a major earthquake fault and was originally built to the better earthquake standards. The recent problems with the main and emergency spillway were not caused by earthquakes.

  5. (sarc on)Don’t worry. The study was funded by a utility company so it’s totally bogus(sarc off).

    • I’ve always wondered. If you forget the end sarc tag, would that make the next post after yours, sarcasm as well?

  6. Despite the comments about the lack of ability to predict a quake, it is well established that the maximum magnitude of a quake is directly related to it’s length. So, if they have gathered seismic data to image the length of the fault & establish that it is much longer than previously thought, and therefore has a larger maximum magnitude potential, this is actionable information for building codes, emergency planning scenarios , etc.

  7. “Further study is warranted to improve the current understanding of hazard and potential ground shaking posed to urban coastal areas from Tijuana to Los Angeles from the NIRC fault,” the study concludes.

    Now where have I heard that before?. Mind you in this case it is warranted to a point. Everybody knows that eventually a devastating earthquake is going to happen. It could be California, Cascadia or even the Mississippi valley. I would think the money should be going to preparation as in moving people away from certain areas . FE The cascadia event is overdue but it is estimated 15,000 people would die because of the resulting tsunami ( could be way worse in the summer), why are people allowed to live in those areas in the first place?

    • @asybot 3:48
      Regarding living along the WA & OR coast and the possibility of a massive earthquake and tsunami it was not known until a few years ago that such a thing had happened. Well, the natives knew from their oral histories, but until the man linked to below did the work there was no scientific knowledge:
      Brian Atwater

    • In this case it is warranted. The study of this fault system came up with data that showed a particular fault zone near a populated area is capable of creating an earthquake that is substantially bigger than previously believed. Studying other areas off the coast might reveal other, similar zones. If I were in charge of disaster planning in that area, I would be interested in funding such studies.

  8. How would they make such an estimate 7. 3-7.4! Did they measure the shear stress level? If the fault moved more slowly the strength would be lesser, or if it was lubricated with seawater or bitumen which is abundant offshore it would similarly reduce it’s energy. The last one was 6.3. A 7.3 one is ten times as strong. Scientists have learned to make scary stuff up to satisfy the impact factor favored by publications. And since the last time it moved before the recent one was 5000years, you want generations of citizens to stress themselves out over there this. A time limit on these types of concerns should be required or they are useless! If it is just of academic interest like the sun is going to fry us in a few B yrs, OK. Science needs more than a reset,. It needs repeating and replacing!

    • Repeating – dang illiterate lefty electronics screws up what you are trying to say.

    • Repealing – dang illiterate lefty electronics screws up what you are trying to say.

    • I believe that geophysicists put decimal points in their forecasts to show they have a sense of humor. H/T William Gilmore Simms

      • Hahaha :-)

        Actually, one puny decimal point increase in seismic moment magnitude corresponds to over 3x the energy released, so the “precision”, given that it’s a logarithmic scale, is a bit deceptive. 3x is a lot.

    • @Gary Pearse :
      “Did they measure the shear stress level?”

      Actually , it appears they have.
      From the Abstract:
      “Coulomb stress change along the fault zone are presented to examine the potential extent of future earthquake ruptures on the fault zone, which appear to be dependent on the location of rupture initiation and fault geometry at the stepover”

      Don’t be so quick to dismiss everything science presented here, just because it is presented here. With time, there seems to be an increased tendency of commenters on this blog to do just that. Read up, give it some critical thought, then comment.

      • This is one of my biggest complaints regarding the so called climate scientists.
        They have made people skeptical of all science.

    • Size of an earthquake is closely related to how much of a fault ruptures. Maximum energy is calculated based on this.

  9. Poor California. Floods. Earthquakes. And worst of all… Jerry Brown.
    They’ve really fallen on hard times…

  10. When the Atomic testing ended and the Scripps Institution lost funding to research the weather impact from Atomic explosions, they switched to Climate Change caused by CO2 and ran with it as long as the Federal money rolled in. Now that Trump and the Republican Congress is set to cut that research funding, Scripps needs a new area to collect research grants. Earthquakes and Tsunamis. Ahh, that’s a good one. Send us money, Washington.

    • “… Climate Change caused by CO2 and ran with it as long as the Federal money rolled in.

      Might I suggest any of these should move to Ocean Shores WA and study tsunamis, aka big harbour waves.

      • Use Google Earth and Street View with this location: 46.972183, -124.170342

        In years past when I’ve been vacationing on the Washington coast, I’ve gotten my truck stuck in the sand on that very beach. When the Cascadia Big One happens, the Grays Harbor area alone will lose 5,000 to 8,000 people straight away. Further south, Ilwaco, Long Beach, and the low-lying parts of Astoria, they’ll all be completely destroyed. There is no way so many people can get out of where they are living and working in the short time they will have before the tsunami comes ashore.

  11. Perfect storm for California this Spring: massive flooding, major earthquake, disruption of communications, power supplies, rails, roadways, food distribution systems. The rest of the US needs to be prepared to receive a million California refugees. It seems pretty certain no other countries in the world will take them.

  12. The epicenter of the 1933 Long Beach was actually just off the Balboa Pier in Newport Beach. Apparently most of the damage was to unrienforced masonary structures. I read an article many years ago about the Newport Inglewood fault being the most dangerous fault in Southern California because of all that is built near it. Earth quakes as strong as 7.8 are not that uncommon on faults here in Southern California. The epicenters are miles below the surface and it is doubtful that a change in average surface temperature of a few tenths of a degree C has any effect on fault movement.

    • Evidently you don’t understand the process. It is not how much the temp changes, it is the fact that it did change. Therefore it is global warming and therefore deserving of research funds. /sarc off

  13. There will ALWAYS be earthquakes, if time is long enough everywhere on earth has or will ‘feel’ an earthquake, Some earthquakes are/will be larger than others, some will be in the magnitude 7.4-7.5 range. There is a high probability (whatever that means) that a 7.5 or larger earthquake WILL occur in California (SOMETIME!).
    Send money for a further study/report.
    Now go back to sleep.

  14. Not to worry,for according to the anti-Fracking forces and our useless idiots from the media..

    Fracking causes earthquakes.

    Therefor we need only drill and frac at selected points and we can relieve the building stress..triggering controlled earthquakes..on time and on budget.
    Never again need California residents fear the “Big One”.

    Sarcasm off.

  15. I have done my own calculations and have found that this fault zone COULD cause an earthquake of 7.0835925 magnitude.

  16. Oh strewth! A model! Any active fault has the potential to do that. It’s not a question of if, but when.

    • The point of this study is that the end points of two faults are closer to each other than previously believed, which increases the chance that an earthquake that starts on one could transfer to and continue on the other. Which means the max earthquake from this system is bigger than previously thought.

  17. I actually made a mental note on reading the start of this to expect someone to blame CO2 for causing earthquakes as a gag, but Lo and behold…
    Anyone actually tried heating a piece of rock, it’s a bit energy intensive to put it mildly, except for the black ones which seem to catch fire nicely after a short while.
    Is there anything that CO2 can’t be blamed for? Perhaps we should make a list to save time…
    Oh, it can’t be blamed for my football club being so crap, can it?

  18. Interesting fact:
    there is some indication from my results suggesting that warming in the NH, especially on the north pole, can partly be blamed on earth’s inner core moving north east. That this is happening can be shown by the movement of the magnetic north pole north east and by taking a lift here down in our gold mines notice the elephant in the room….
    In the case of LA, I would not be worried so much about the movement of earth’s inner core north, but I would be about the movement east. I think that is going to cause extra stress. There is some indication that the magnetic north pole will soon be on Canadian territory.

      • Volcanic eruptions in Iceland are not indicative of a mythical movement of the Earth’s core to the northeast.

      • Iceland has always gone through periods of enhanced volcanic activity followed by periods of less activity.
        Nothing unusual.
        PS: If the core had moved, the scientists who study it would have noticed.

      • If the core moved to a substantially different location, we would all be dead.

        Iceland is only about 15 million years old. It sits on the Mid-Atlantic Ridge, over a mantle plume. Iceland rarely goes five years without a significant eruption.

      • @david &

        Records indicate that the pole’s location barely moved in the early decades, but in about 1904, it began tracking north-east at a rate of about nine miles a year. That speed increased significantly from about 1989, possibly because of a “plume” of magnetism deep below ground. The pole is now believed to be heading towards Siberia at about 37 miles each year. “Earth’s magnetic field is changing in time. And as far as we know, it has always been changing in time,” geophysicist Jeffrey Love of the US Geological Survey in Colorado told Discovery News, which investigated the issue last week…..
        http://www.independent.co.uk/news/science/adjust-your-compass-now-the-north-pole-is-migrating-to-russia-2233610.html

        …..there are none so blind as those who do not want to see what is happening….

        to our inner core.

      • Good fracking grief… Magnetic drift of the poles has nothing to do with the Earth’s core moving around.

        https://www.ngdc.noaa.gov/geomag/GeomagneticPoles.shtml

        Magnetic polar drift is the reason why topo maps and navigational charts have always had to be updated for magnetic declination.

        The solid inner core rotates inside the liquid outer core. The magnetic field is generated in the outer core.

        http://www.pbs.org/wgbh/nova/magnetic/reve-drives.html

        The increase in the rate of magnetic drift might be indicative of an upcoming polarity reversal… But this also has nothing to do with the core moving to a new location. It’s something the magnetic field has done many times throughout geologic history.

        The intensity and polarity of Earth’s magnetic field is always changing.

    • henry said
      I think that is going to cause extra stress. There is some indication that the magnetic north pole will soon be on Canadian territory
      henry says
      my bad.
      should be Siberia, apparently

      • but the direction apparently still is north east….
        Not good for LA

        was it not Nostradamus who predicted the end of the ‘city of angels’ by some terrible disaster?

      • @david
        surely
        you must realize that the change in the magnetic north pole must be related to the movement of earth’s inner core?
        @all
        anyone else here who agrees with david’s notion that this movement has nothing to do with it?

      • Actually there is no reason to assume that the moving pole is caused by anything other than shifts in the magnetic field.
        The core remains where it has always been, at the center of the earth where it is locked in place by gravity.

  19. In 2013, Scripps research vessel New Horizon towed a hydrophone array to map the bathymetry of the Newport-Inglewood/Rose Canyon fault zone.
    CREDIT
    Scripps Institution of Oceanography at UC San Diego

    Any bets as to whether it was also towing an an airgun?

    • David, looks like they used a sparker source for this which makes sense, I think, given that the goal was to acquire high(er) resolution imaging of the near sea bottom.

      Also interesting that they recently sold the ’60s vintage vessel. I suspect that its replacement will possess modern seismic technologies and be capable of handling a variety of source types… including the dreaded airgun. ;-)

      http://www.marine-geo.org/portals/seismic/news.php

      • Yeah, it probably was a sparker… Which has the same mythological effect on marine life as an airgun.

  20. More alarmism!

    LA hasn’t seen a quake in years… the quake trend in LA is clearly down. /sarc

    • Poor Griffie, the strain of finding something relevant to say has caused his final neuron to commit suicide.

  21. One thing I have noticed is that the quake pattern of the last several years has deviated over the last several weeks. Magnitude 5.0+ quakes have been popping off every few days or over successive days in a row, and out of synch with the Full/New Moon where one would typically see them. Does this portend anything? Unknown. Either it is a good thing that the plates are releasing stress, or it could be a precursor to a larger quake.

  22. When the San Onofre nuclear power plant was being projected in the 1960s, the consulting firm for which I then worked, along with Charles Richter, conducted a study of earthquake and tsunami potential at the site. As I recall, our conclusion regarding maximum likely earthquake magnitude offshore over the next 100 years was Richter 7.25 and a maximum tsunami run-up at the site of ~4 meters..

    The latter estimate was strongly objected to by the licensing agency of the federal government, which claimed that it was at least 3 times too low. In fact, during the life of the now-closed power plant, no run-up ever exceeded ~1 meter.

    There’s precious little difference in the findings of the current study insofar as the geophysical situation is concerned. What remains to be seen is whether a huge difference will persist between purely scientific findings and the public stance of regulatory agencies.

  23. Has anyone carried out a cost benefit analysts of the entire State of California sliding into the pacific?

    • CA won’t slide into the ocean. It will eventually slide “north to Alaska,” where it will frack up another oil producing State.

  24. Over time, blind thrust faults under actual populated areas will ultimately cause more damage in SoCal and will even yield substantial damage further North (hello Coalinga). There are even some here in the Bay Area. The thing about Strike Slip quakes is there is minimal vertical acceleration. That’s a best case scenario for many structures.

    • I thought it was side to side vibration that destroyed buildings.
      I know that the earthquake simulators that they use to test building design concentrate on horizontal movements.

      • Its both vertical and horizontal movements in an earthquake that stress buildings. I was in construction for some 30 years, and lived through the Loma Prieta earthquake in 1988. It was the racking forces that damaged frame structures without adequate wall ties to the roof, or between stories. There were also problems with inadequate sheer wall design. Concrete structures, like that elevated freeway in Oakland, mostly failed due to inadequate/improper reinforcement steel.

  25. I grew up in San Diego and now live in Orange County. I’ve long wondered if the two fault systems were one; it is interesting to find out that they are.

Comments are closed.