5 ms·

I heard that smaller (relative) earthquakes actually lower the prob of larger ones, so maybe it is a good thing? A bunch of 7.X earthquakes in the ocean are not

I heard that smaller (relative) earthquakes actually lower the prob of larger ones, so maybe it is a good thing? A bunch of 7.X earthquakes in the ocean are not going to be hugely destructive.

jacquesm 11mo ago
That's correct, if relatively small earthquakes would stop that could be the precursor to a much bigger one. It's like releasing tension gradually rather than all at once.
- tonmoy 11mo ago
  Isn’t that a myth? Do you have any sources to back up your claim?
  - indigodaddy 11mo ago
    Various scientists in this video. The video is a great watch btw. https://youtu.be/HBluLfX2F_k https://youtu.be/HBluLfX2F_k (stresses build up and are often released through many small, unfelt earthquakes (25:54). If these small movements don't dissipate the stress, it can accumulate and lead to a powerful chain reaction (26:25) * disclaimer I used YouTube's built-in AI to find/summarize the timestamps, as I couldn't remember offhand where it was when I previously watched this.
    - mturmon 11mo ago
      I don't believe the video quite says this (I watched the relevant section). It's worth noting that they are mostly interested in critical phenomena in general, and earthquakes are kind of a drive-by application, treated along with fires and sand piles. They do hint around the edges, but they don't head-on make the claim for earthquakes that small EQs materially lessen stress buildup and thereby make larger EQ's less likely. I was looking for a credential of one of the people they interview, to see if they are really a solid earth person or more of a critical phenomena person -- their names aren't easy to find. This particular myth ("small earthquakes relieve stress") is a bit of a stinker in the solid earth community, and I think a solid earth person would be quite careful about their words as they discuss this.
      - indigodaddy 11mo ago
        I think you've summed it up correctly. It's not proof and some scientists claiming some things isn't the same as studies/evidence. However, is there evidence that it's not true? The fact is we do have these smaller movements and earthquakes quite regularly, so we don't really know what would happen after a long absence of them (do we? I suppose there are simulations perhaps that could be run? But I don't know that that's proof either way). To me though it makes a lot of sense that it would/could spur a huge event.
  - __s 11mo ago
    Seems like it, & each rank is 30x more energy than the last[1] https://www.usgs.gov/faqs/what-probability-earthquake-a-foreshock-a-larger-earthquake https://www.usgs.gov/faqs/what-probability-earthquake-a-fore... Suggests 5% for larger quake to follow within week. But overall most sources I could find suggested it's hard to know, needs more research 1: https://www.reddit.com/r/askscience/comments/10wecl8/do_little_earthquakes_prevent_big_earthquakes https://www.reddit.com/r/askscience/comments/10wecl8/do_litt...
  - jacquesm 11mo ago
    https://www.geo.ruhr-uni-bochum.de/en/new-study-connects-earthquake-energy-release-strength-rocks-beneath-our-feet https://www.geo.ruhr-uni-bochum.de/en/new-study-connects-ear...
    - criddell 11mo ago
      https://news.caloes.ca.gov/earthquake-myths-separating-fact-from-fiction/ https://news.caloes.ca.gov/earthquake-myths-separating-fact-... Myth 5 is "Small Earthquakes Relieve Pressure and Prevent Larger Ones"
      - jacquesm 11mo ago
        Myth: new knowledge never trumps old knowledge. Check the dates on those two publications.
      - fc417fc802 11mo ago
        GP is correct; I'm not sure why CA gov is calling that a myth (it's not). However keep in mind that it's not necessarily true 100% of the time. Or at least the things it might seem to imply at first glance aren't true - the presence or absence of small quakes in a given period doesn't necessarily tell you anything useful about the future.
        jacquesm 11mo ago
        Indeed. But I get why people are confused because it is a subtle difference between 'stress relieved through small earthquakes is stress expended' vs 'stress relieved through small earth quakes is not indicative of the magnitude of future events'. The long term absence of stress relief small quakes on a known fault line might be bad news, or no news at all, statistics are where the difference is here, not in particular events. See also, 'the big one' and various theories around it.
    - mturmon 11mo ago
      I think you intended this to be a validation of the idea that small quakes relieve stress and therefore lower the chance of a large quake. The above link does not answer that question. It is relating stress release to "fault strength", or the maximum shear stress that can be withstood by the fault. There is an incidental relationship with depth that plays a role. The video linked nearby (on criticality) also does not address the question at issue. I'm only replying because I work adjacent to this area, and my understanding is that the idea that small EQ's release stress is a myth. Here [1] is another link, listed as #1 in the "Myths" category. And you can dig up quotes from none other than Lucy Jones [2] saying that this is a myth. I don't work directly in this area, so I'm not willing to say absolutely no. But I'd really like to see a head-on reference supporting the claim that it's not a myth. [1] https://earthquakes.berkeley.edu/outreach/faq.html https://earthquakes.berkeley.edu/outreach/faq.html [2] https://en.wikipedia.org/wiki/Lucy_Jones https://en.wikipedia.org/wiki/Lucy_Jones
  - numpad0 11mo ago
    This type of argument is kind of logical but not so immediately useful. Earthquakes just happen and no one is involved in that process. There could still be the big one coming, or that one might have been defused by this one. No one knows.
lostlogin 11mo ago
> A bunch of 7.X earthquakes in the ocean are not going to be hugely destructive. New Zealand’s 5th most deadly disaster was Christchurch’s 6.2 which killed 185 people. It was a shallow aftershock from a larger, less destructive quake. The damage was huge. https://en.wikipedia.org/wiki/2011_Christchurch_earthquake https://en.wikipedia.org/wiki/2011_Christchurch_earthquake
- y1n0 11mo ago
  The key phrase in the parent is “in the ocean”
  - lostlogin 11mo ago
    Yeah, I didn’t miss that. It’s a bit academic for a country like New Zealand where the sea is usually pretty close by.
- alex1138 11mo ago
  Leading Sarah Wynn-Williams to decide Facebook was a great idea, to be able to contact people in an emergency, later got dissuaded, wrote a book https://www.amazon.com/Careless-People-Cautionary-Power-Idealism/dp/1250391237 https://www.amazon.com/Careless-People-Cautionary-Power-Idea...
deleted 11mo ago
[deleted]
jansan 11mo ago
That is correct, but OTOH there was a 7.3 foreshock two days before the 2011 Tōhoku earthquake. So the only thing we can say for sure is that it is still extremely difficult to predict earthquakes.
Someone 11mo ago
On the one hand earthquakes remove tension from the earth’s crust and release energy that can’t be used in future shocks. On the other hand, if a shock doesn’t release all energy it may come to rest in a relatively weak spot that will soon give away again (https://en.wikipedia.org/wiki/Earthquake_swarm https://en.wikipedia.org/wiki/Earthquake_swarm: “The Matsushiro swarm lasted from 1965 to 1967 and generated about 1 million earthquakes. This swarm had the peculiarity of being sited just under a seismological observatory installed in 1947 in a decommissioned military tunnel. It began in August 1965 with three earthquakes too weak to be felt, but three months later, a hundred earthquakes could be felt daily. On 17 April 1966, the observatory counted 6,780 earthquakes, with 585 of them having a magnitude great enough to be felt, which means that an earthquake could be felt, on average, every two and a half minutes.”) Because of that, I think an earthquake will increase the probability of one occurring again soon, but decrease its strength.
xvedejas 11mo ago
Almost all energy released in earthquakes is released in the biggest ones. No realistic number of smaller quakes is ever going to add up to even the single biggest earthquake ever recorded.
- ed 11mo ago
  To dissipate the energy of a M9 (which happens about once per decade) you'd need about 32,000 quakes of M6 (still big enough to collapse buildings). Energy scales as 10^(1.5 × ΔM) ΔM = 9.0 − 6.0 = 3.0 10^(1.5 × 3) = 10^4.5 ≈ 31,600

I heard that smaller (relative) earthquakes actually lower the prob of larger ones, so maybe it is a good thing? A bunch of 7.X earthquakes in the ocean are not going to be hugely destructive.

jacquesm 11mo ago

That's correct, if relatively small earthquakes would stop that could be the precursor to a much bigger one. It's like releasing tension gradually rather than all at once.

tonmoy 11mo ago
Isn’t that a myth? Do you have any sources to back up your claim?
- indigodaddy 11mo ago
  Various scientists in this video. The video is a great watch btw. https://youtu.be/HBluLfX2F_k https://youtu.be/HBluLfX2F_k (stresses build up and are often released through many small, unfelt earthquakes (25:54). If these small movements don't dissipate the stress, it can accumulate and lead to a powerful chain reaction (26:25) * disclaimer I used YouTube's built-in AI to find/summarize the timestamps, as I couldn't remember offhand where it was when I previously watched this.
  - mturmon 11mo ago
    I don't believe the video quite says this (I watched the relevant section). It's worth noting that they are mostly interested in critical phenomena in general, and earthquakes are kind of a drive-by application, treated along with fires and sand piles. They do hint around the edges, but they don't head-on make the claim for earthquakes that small EQs materially lessen stress buildup and thereby make larger EQ's less likely. I was looking for a credential of one of the people they interview, to see if they are really a solid earth person or more of a critical phenomena person -- their names aren't easy to find. This particular myth ("small earthquakes relieve stress") is a bit of a stinker in the solid earth community, and I think a solid earth person would be quite careful about their words as they discuss this.
    - indigodaddy 11mo ago
      I think you've summed it up correctly. It's not proof and some scientists claiming some things isn't the same as studies/evidence. However, is there evidence that it's not true? The fact is we do have these smaller movements and earthquakes quite regularly, so we don't really know what would happen after a long absence of them (do we? I suppose there are simulations perhaps that could be run? But I don't know that that's proof either way). To me though it makes a lot of sense that it would/could spur a huge event.
- __s 11mo ago
  Seems like it, & each rank is 30x more energy than the last[1] https://www.usgs.gov/faqs/what-probability-earthquake-a-foreshock-a-larger-earthquake https://www.usgs.gov/faqs/what-probability-earthquake-a-fore... Suggests 5% for larger quake to follow within week. But overall most sources I could find suggested it's hard to know, needs more research 1: https://www.reddit.com/r/askscience/comments/10wecl8/do_little_earthquakes_prevent_big_earthquakes https://www.reddit.com/r/askscience/comments/10wecl8/do_litt...
- jacquesm 11mo ago
  https://www.geo.ruhr-uni-bochum.de/en/new-study-connects-earthquake-energy-release-strength-rocks-beneath-our-feet https://www.geo.ruhr-uni-bochum.de/en/new-study-connects-ear...
  - criddell 11mo ago
    https://news.caloes.ca.gov/earthquake-myths-separating-fact-from-fiction/ https://news.caloes.ca.gov/earthquake-myths-separating-fact-... Myth 5 is "Small Earthquakes Relieve Pressure and Prevent Larger Ones"
    - jacquesm 11mo ago
      Myth: new knowledge never trumps old knowledge. Check the dates on those two publications.
    - fc417fc802 11mo ago
      GP is correct; I'm not sure why CA gov is calling that a myth (it's not). However keep in mind that it's not necessarily true 100% of the time. Or at least the things it might seem to imply at first glance aren't true - the presence or absence of small quakes in a given period doesn't necessarily tell you anything useful about the future.
      - jacquesm 11mo ago
        Indeed. But I get why people are confused because it is a subtle difference between 'stress relieved through small earthquakes is stress expended' vs 'stress relieved through small earth quakes is not indicative of the magnitude of future events'. The long term absence of stress relief small quakes on a known fault line might be bad news, or no news at all, statistics are where the difference is here, not in particular events. See also, 'the big one' and various theories around it.
  - mturmon 11mo ago
    I think you intended this to be a validation of the idea that small quakes relieve stress and therefore lower the chance of a large quake. The above link does not answer that question. It is relating stress release to "fault strength", or the maximum shear stress that can be withstood by the fault. There is an incidental relationship with depth that plays a role. The video linked nearby (on criticality) also does not address the question at issue. I'm only replying because I work adjacent to this area, and my understanding is that the idea that small EQ's release stress is a myth. Here [1] is another link, listed as #1 in the "Myths" category. And you can dig up quotes from none other than Lucy Jones [2] saying that this is a myth. I don't work directly in this area, so I'm not willing to say absolutely no. But I'd really like to see a head-on reference supporting the claim that it's not a myth. [1] https://earthquakes.berkeley.edu/outreach/faq.html https://earthquakes.berkeley.edu/outreach/faq.html [2] https://en.wikipedia.org/wiki/Lucy_Jones https://en.wikipedia.org/wiki/Lucy_Jones
- numpad0 11mo ago
  This type of argument is kind of logical but not so immediately useful. Earthquakes just happen and no one is involved in that process. There could still be the big one coming, or that one might have been defused by this one. No one knows.

lostlogin 11mo ago

> A bunch of 7.X earthquakes in the ocean are not going to be hugely destructive. New Zealand’s 5th most deadly disaster was Christchurch’s 6.2 which killed 185 people. It was a shallow aftershock from a larger, less destructive quake. The damage was huge. https://en.wikipedia.org/wiki/2011_Christchurch_earthquake https://en.wikipedia.org/wiki/2011_Christchurch_earthquake

y1n0 11mo ago
The key phrase in the parent is “in the ocean”
- lostlogin 11mo ago
  Yeah, I didn’t miss that. It’s a bit academic for a country like New Zealand where the sea is usually pretty close by.
alex1138 11mo ago
Leading Sarah Wynn-Williams to decide Facebook was a great idea, to be able to contact people in an emergency, later got dissuaded, wrote a book https://www.amazon.com/Careless-People-Cautionary-Power-Idealism/dp/1250391237 https://www.amazon.com/Careless-People-Cautionary-Power-Idea...

deleted 11mo ago

[deleted]

jansan 11mo ago

That is correct, but OTOH there was a 7.3 foreshock two days before the 2011 Tōhoku earthquake. So the only thing we can say for sure is that it is still extremely difficult to predict earthquakes.

Someone 11mo ago

On the one hand earthquakes remove tension from the earth’s crust and release energy that can’t be used in future shocks. On the other hand, if a shock doesn’t release all energy it may come to rest in a relatively weak spot that will soon give away again (https://en.wikipedia.org/wiki/Earthquake_swarm https://en.wikipedia.org/wiki/Earthquake_swarm: “The Matsushiro swarm lasted from 1965 to 1967 and generated about 1 million earthquakes. This swarm had the peculiarity of being sited just under a seismological observatory installed in 1947 in a decommissioned military tunnel. It began in August 1965 with three earthquakes too weak to be felt, but three months later, a hundred earthquakes could be felt daily. On 17 April 1966, the observatory counted 6,780 earthquakes, with 585 of them having a magnitude great enough to be felt, which means that an earthquake could be felt, on average, every two and a half minutes.”) Because of that, I think an earthquake will increase the probability of one occurring again soon, but decrease its strength.

xvedejas 11mo ago

Almost all energy released in earthquakes is released in the biggest ones. No realistic number of smaller quakes is ever going to add up to even the single biggest earthquake ever recorded.

ed 11mo ago
To dissipate the energy of a M9 (which happens about once per decade) you'd need about 32,000 quakes of M6 (still big enough to collapse buildings). Energy scales as 10^(1.5 × ΔM) ΔM = 9.0 − 6.0 = 3.0 10^(1.5 × 3) = 10^4.5 ≈ 31,600