Skip to main content

Silent earthquakes are tied to changes in fluid deep below Cascadia's fault

earthquakes, slow earthquakes, backwards earthquakes, seismology, geophysics, cascadia subduction zone, cascadia fault line, pacific northwest earthquakes
A schematic drawing of the Cascadia subduction zone. New research suggests that tiny, imperceptible quakes in the region are connected to the movement of fluid deep below the surface.
(Image: © USGS.)

Every 14 months, silent earthquakes ever-so-slightly rattle the Cascadia subduction zone, which is capable of producing a magnitude 9.0 earthquake. Now, research shows that these so-called aseismic quakes are tied to fluid moving miles underground.

These findings don't affect what we know about the risk of a dangerous quake in the Cascadia region; that information is well-known from the cycle of stress build-up and release during large earthquakes, said Pascal Audet, a geophysicist at the University of Ottawa and a co-author of the new research. A better understanding of the aseismic quakes could eventually help bridge the gap in understanding between this well-observed earthquake cycle and the processes happening deep within the subduction zone

Related: The 10 biggest earthquakes in history

The new study, published Jan. 22 in the journal Science Advances, looked at the Cascadia subduction zone, a seismically active region spanning from northern California to Vancouver Island, in which the oceanic Juan de Fuca plate is sliding under, or subducting under, western North America. According to the Oregon Office of Emergency Management, the area has experienced earthquakes of magnitude 9.0 in the past and has the potential to experience quakes of similar or larger sizes in the future. A massive earthquake in the region could also trigger a tsunami of up to 100 feet (30.5 m). 

The inner workings of the fault system, though, are still challenging to understand. Researchers now have sensitive ground instruments that can detect extremely slow, subtle movements deep within the subduction zone, Audet said. These instruments have revealed that parts of the fault between the two subducting plates regularly slip, moving slowly over a period of days or weeks. The slip is too gradual to cause noticeable shaking at the ground level, but it can put pressure on new parts of the fault, raising the risk of large earthquakes. 

Researchers also know that the rocks that undergo this slow slip, 25 miles (40 kilometers) down, are saturated with fluid, Audet said. The fluids, trapped within small pores in the rock, are under a great deal of pressure from the rock and Earth above them. This weakens the saturated rock, which may contribute to the slow-slip episodes on the fault. 

The new research investigated the link between the fluids and the slip. Audet and his colleagues compared 25 years of tremor data from southern Vancouver Island with data on rock structure and the pressures many miles down. There were 21 slow-slip earthquake events during that time period. With each imperceptible quake, they found, fluid pressures quickly dropped. 

"This could mean that part of the fluids escapes into the overlying rock mass, or the micro-fractures [in the rock] expand and decompress the fluids to some degree," Audet wrote in an email to Live Science. "This change is very rapid, however, and occurs over a period of days or perhaps weeks." 

The finding is the first direct evidence that the fluids in subduction zones move around during slow slip, Audet said. But now, it's a chicken-and-egg question. It's not clear from the available data whether the fluid movements actually trigger the slow quakes, or whether the fluid moves in response to the slipping of the rocks. 

Audet and his colleagues are now working to see if they can find the same link between fluids and slow slip at other subduction zones across the world. Cascadia is a particularly simple example of slow slip, with the gradual tremors occurring across the entire fault, Audet said; other subduction zones are more complex. Understanding the behavior of fluids during these events, though, could help explain why some subduction zones experience regular slow-slip events and why some are more erratic. 

Originally published on Live Science.

OFFER: Save at least 53% with our latest magazine deal!

With impressive cutaway illustrations that show how things function, and mindblowing photography of the world’s most inspiring spectacles, How It Works represents the pinnacle of engaging, factual fun for a mainstream audience keen to keep up with the latest tech and the most impressive phenomena on the planet and beyond. Written and presented in a style that makes even the most complex subjects interesting and easy to understand, How It Works is enjoyed by readers of all ages.
View Deal

  • 71bronco
    So I’m not a scientist but if we continue to pump crude oil out of the earth are we actually taking away the natural lubrications that were made thru millions of years and this will cause some really bad news such as a 9+ magnitude earthquake on the west coast?
    Reply
  • David Kumo
    No that's not correct, if that were the case we would see a large earthquake or M9 ones happen a lot around the world every other day or month considering the fact that its been more than 150 + years we have pumped up oil and still continue to do so. I have been researching silent quakes for many years now and done many lab tests and the fluids are aqueous and metamorphic fluids in fact there many studies and past scientific work to support this. You should read Pascal Audets countless research work on silent earthquakes that gives evidence on the types of fluids involved e.g hot water, melt, etc. I've read on the fluids type in silent earthquakes and Pascal Audet on Google you will find proof. Additionally You can find evidence here:

    https://pubs.geoscienceworld.org/books/book/1221/chapter/107020974/Metamorphic-Fluids-and-their-Relationship-to-the
    Another evidence: https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/94JB01147
    Reply
  • russellmeans
    71bronco said:
    So I’m not a scientist but if we continue to pump crude oil out of the earth are we actually taking away the natural lubricants that were made thru millions of years and this will cause some really bad news such as a 9+ magnitude earthquake on the west coast?
    Oh yes, that is a unknown. I do think there now have been some studies about this and fracking. No doubt it has to have some consequences. You can go on the computer and draw image of just that. It will show you just what can and will happen in time. Fooling around with these plates can cause a disaster.
    Reply
  • David Kumo
    71bronco said:
    So I’m not a scientist but if we continue to pump crude oil out of the earth are we actually taking away the natural lubrications that were made thru millions of years and this will cause some really bad news such as a 9+ magnitude earthquake on the west coast?
    71bronco said:
    So I’m not a scientist but if we continue to pump crude oil out of the earth are we actually taking away the natural lubrications that were made thru millions of years and this will cause some really bad news such as a 9+ magnitude earthquake on the west coast?
    71bronco said:
    So I’m not a scientist but if we continue to pump crude oil out of the earth are we actually taking away the natural lubrications that were made thru millions of years and this will cause some really bad news such as a 9+ magnitude earthquake on the west coast?
    Read my reply.
    Reply
  • David Kumo
    71bronco said:
    So I’m not a scientist but if we continue to pump crude oil out of the earth are we actually taking away the natural lubrications that were made thru millions of years and this will cause some really bad news such as a 9+ magnitude earthquake on the west coast?

    No that's not correct, if that were the case we would see a large earthquake happen a lot around the world every other day or month in places like Saudia Arabia (biggest oil producer , Norway, Eastern USA, etc) every month considering the fact that its been more than 150 + years we have pumped up oil and still continue to do so. I have been researching silent earthquakes for many years now and done many lab tests and the fluids involved are aqueous and metamorphic fluids, in fact there many studies and past scientific work to support this fact, especially in Subduction zones like Cascadia when the plate sinks under another, a lot of different fluids are generated during the subduction process and have been mentioned in many scientific texts.

    As to answer your question on oil, Earth made oil through ancient organisms to sequester CO2 inside the earth so that oxygen levels could increase in the atmosphere and make life like ours possible.- (You can google this and find tremendous evidence to support this too). Whereas for fluids involved in silent earthquakes, You should read Pascal Audets countless research work on silent earthquakes that gives evidence on the types of fluids involved e.g hot water, melt, etc. Go to google type in Pascal Audet and silent earthquakes you will find countless work published over the years on this. Additionally You can find evidence here:

    https://eos.org/articles/fluid-pressure-changes-grease-cascadias-slow-aseismic-earthquakes
    Metamorphic Fluids and their Relationship to the Formation of Metamorphosed and Metamorphogenic Ore Deposits | Metamorphic and Metamorphogenic Ore Deposits | GeoScienceWorld Books | GeoScienceWorld
    Abstract. Metamorphic rocks produce fluids as devolatilization occurs during prograde metamorphism or as melts (which act as temporary repositories for fluids)
    pubs.geoscienceworld.org

    Another evidence: https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/94JB01147
    Reply
  • David Kumo
    russellmeans said:
    Oh yes, that is a unknown. I do think there now have been some studies about this and fracking. No doubt it has to have some consequences. You can go on the computer and draw image of just that. It will show you just what can and will happen in time. Fooling around with these plates can cause a disaster.

    Actually each time we subtract something from beneath the earth and dig it out- or each time we add something to it, it causes a pressure shift, and shifts the pressure on rocks in the ground, which causes earthquakes, this is evidenced from mining of all sorts- e.g gold, metal ores, water extraction even (if we extract a lot) as far goes for fracking..the amount of water drilling companies throw down on the rocks no doubt it will cause movement!
    Reply
  • seismo-q
    Actually no, that's not how it works. I'm a seismologist and subduction earthquakes are a different beast. They occur on large faults and are one of the earth's recycling machines in the birth and death process of continents and oceans. Induced seismicity from fracking is real but not anywhere near a 9.0.
    Reply
  • russellmeans
    seismo-q said:
    Actually no, that's not how it works. I'm a seismologist and subduction earthquakes are a different beast. They occur on large faults and are one of the earth's recycling machines in the birth and death process of continents and oceans. Induced seismicity from fracking is real but not anywhere near a 9.0.
    Time my friend, time.
    Reply
  • FreeBra1n
    admin said:
    Fluid pressures in the Cascadia subduction zone are ed to regular, imperceptible earthquakes.

    Silent earthquakes are tied to changes in fluid deep below Cascadia's fault : Read more

    This probably adds credibility to the theory of Moon Phases (Full and New) and extreme Tides correlating with bigger quakes in a Japanese study published by Nature.... The study covers 15 years after the Japan Tsunami...

    I ve noticed a pattern in Puerto Rico in the last months, with bigger tremors when It was very unstable ...and every 2 weeks we had bigger quakes. (I can just imagine Tidal bore waves, following the Moon underground and fluids moving between crevices and caverns). I bet it could be an important factor...
    Reply