The scale of geological time never ceases to impress:
“There was plenty of accumulated stress, enough to permit a quake with 3 m (10 ft) of slip. That suggests that one can, indeed, have aftershocks 150 years after very large mainshocks”
What I don’t get is how is a quake which happens on a disconnected and different fault (heretofore unknown) an aftershock of a previous quake (which occurred over 100 years ago)?
I looks like quakes are on a continuum. The extremes are, each quake is an individual event; on the other all quakes are a result and continuation of previous quakes. It seems like the slider position on the continuum is up to a bit of “interpretation”.
As a person that knows nothing about this subject, that's the impression I got as well. The tectonic plates are constantly moving, so of course earthquakes in one place will often cause stress in another place. Understanding this process is certainly important, though.
While plants are moving over 1cm per year that’s not all across a single fault. If you look at a map of them California has an extensive fault network which means it takes far longer than 100 years for a single fault to build up 3m worth of stress.
Thus, you can have multiple points of stress all linked where it’s not obvious which one is going to slip first, but they are likely to cluster over relatively short periods. Where 100 years can still be considered short.
The writing and research following this quake series has again underscored for me both a) how little we actually know about predicting earthquakes b) and how frustrating that is. You can read every article out there about the things, and each one ends with, roughly, shrug. As somebody who derives a sense of control from knowledge, it's extra terrifying to have something with such a huge potential impact on me completely in the dark.
Right there with you. My wife keeps asking me questions about it and she seems dumbfounded that my relaying of information via research generally ends with "we just don't know how it works".
It seems to me like we've recently (~15-30yrs) had a lot of new technology deployments (and accessibility to the underlying data that's produced) which might considerably help us with gaining an understanding over time. Things like high-resolution, high-precision aerial & satellite radar/lidar/photography and the like.
I tend to think it's just a function of time at this point, but on geological time scales that may still take quite a while I suppose.
1. Hold your hands together, palms open, as if you were praying.
2. Press them together very hard, and at the same time try to slide them past one another.
3. Predict exactly when they will slip, by how much, and how loud the sound will be. To be roughly to scale, it must be with millisecond [0] and millimeter [1] accuracy.
[0] Assuming avg. 100 years between quakes, prediction accurate to a week, avg. 5 seconds before hands slip, then 100 yrs * 52 weeks : 1 week ~ 5,000:1 ~ 5 sec : 1 msec.
[1] A 150 KM fault with a prediction of slip accurate to 0.5 M movement is 300,000:1. For a hand span of 150 mm that would equate to 0.5 um. On the other hand (pun intended), we could compare maximum slippages; assuming an earthquake movement max of 20 M and a hand slippage max of 0.2 M, a real-world resolution of 0.5 M would equate to a hand-slip prediction accurate to 2 mm.
I don't see the point worrying about things outside of your control. Solar storms, nuclear war, infectious diseases, asteroids, any number of other unknown natural phenomena we know nothing about. Mitigate what you can, try to help others, but accept that at the end of the day, you (and the rest of humanity) are most likely inconsequential in the story of the universe.
I'm just a casual ham radio operator, military history hobbyist, amateur health science researcher, and I know a tiny bit about space. But it seems the four types of disasters you mention have been studied and measured in depth, with the result bring great impact on our vulnerability to them. Is this not so, and should we not continue improving our measurement (control) systems?
We should strive to improve our model of the universe, but I was specifically responding to the notion of being “terrified” by the person I responded to. I think am not terrified by it because I’ve accepted that there are always any number of risks that can wipe me out, known and unknown.
Is it not? As far as I know, it’s plausible a new bacteria, fungus, or virus could develop and we can’t figure out how to fight it, or at least not quickly enough.
Anything is possible, but I’m not saying we can’t or shouldn’t fight it or take steps to prevent it or mitigate damage from it. I’m saying no point in being worried about it.
(sorry there is no reply option for lots of pulp).
Isn't worry the one human emotion that actually makes us ready for things. If we had an earthquake 1000 years ago that killed half of society and the people just said, damn oh well. They don't do things the same way after that do they? They change design, learn more about the planet, adjust adjust adjust. All of that is driven by worry.
Perhaps worry is not the right word, as the person I initially responded to had used the word “terrified”. As in I wouldn’t dwell on things out of my control.
It is not from lack of trying. Geophysicists have been trying for 50 years. There was a glimmer of hope when I started grad school with Russians promoting pre-quake velocity anomalies and radon emissions anomalies. And Chinese promoting animal behavior. Neither were reproducible or reliable after extensive study.
Then prediction research became the black death of academic careers with little progress.
This century a milder version called 'earthquake forecasting' has gained acceptance. That is more big data and statistical odds.
Plus 'early warning' seeks to detect quakes and warn people at the speed of light, seconds before damaging waves arrive at the speed of sound.
One thing I noticed is that when the US talks about earthquakes, it often only notes the seismic magnitude value of the quake and doesn't always mention the seismic intensity scale values of the affected locations. This is in contrast to Japan where quakes are almost always mentioned in both magnitude and the Japan Meteorological Agency's "shindo" intensity scale [1], eg. "The 2011 Tohoku Earthquake was a M9.0 quake with a maximum intensity of shindo 7." The US does have the equivalent of the JMA shindo scale - the Modified Mercalli (MM) scale [2], and they do seem to be used, but I see the MM values mentioned much less frequently than how both the Japanese agencies and the general public refers to shindo values.
While the magnitude value signifies the overall energy of the quake, intensity scale values indicate the shaking intensity of a given location; hence, it feels more grounded in one's daily life experiences. Many Japanese individuals have developed an approximate sense of how strong a quake is - conversations like "That was a bit big, somewhere around shindo 4?" are common after quakes. People do of course care about magnitude, but the thing they care most about after a big quake is more likely "what was the seismic intensity in the worst-hit area?"
Any idea why intensity scales seem to be much less common in the US?
It might be a data collection problem--the JMA has deployed a pretty dense network of sensors over their entire territory, which makes sense given how geologically active it is.
In fact the Earthquake Early Warning's "next steps" plan says "New sensors need to be added in California to shorten the CISN sensors spacing to approximately 12 miles to facilitate timely EEW. The shorter the station spacing, the smaller the blind zone will be because warnings can be issued faster."
Probably because the average Japanese person experiences a lot more earthquakes than the average American even those in the highest risk areas. It's much harder to get a feeling for a value on a particular earthquake scale if you only experience 2 in your lifetime.
If you live in California, you'll experience more than two earthquakes per year (hell, SoCal just had two reasonably strong ones over a span of two days). It's certainly enough to develop an intuition around relative amounts of shaking.
Yeah I don't generally either. I live north of the Bay Area and the last quake I remember feeling there was the Napa one in 2014. I believe it was somewhere between a 5.5 and 6.0.
I went to school in the LA Inland Empire area - there was a quake I felt last year there during class. It was really close but I'm pretty sure it was just short of 4.0.
We have hundreds (thousands?) of quakes per year, but the likelihood your average resident feels a quake in any given year? I think it's low.
I have lived in the bay area for 7 years (2012-2019). I have never felt an earthquake. I recall a few happening (from news reports, twitter), but I either didn't feel them or they happened at night while sleeping.
The only time I've felt the ground shake was in the earthquake simulator at the California Academy of Science in SF :)
The Hayward fault seems to have the most seismic activity lately. You'll feel them 2+ times a year in the East Bay--especially if you're in an older, multi-story building when it strikes.
You're misrepresenting things by mentioning the two recent earthquakes. Most earthquakes come in waves, quite literally, so it was almost expected that the first one might be followed be another.
I remember in my "lyceum" years (15-17) among many other geological studies we were taught the significance and uniqueness of the Richter Vs Mercalli scales. It always surprised me how in Europe you never hear of the Mercalli scale and its importance to assess. I assume it is (as some others mentioned below) the lack of the necessary wide-scale of sensors that need to be deployed throughout certain seismogenic areas that tend to be wide (e.g. majority of Italy, Greece). Good to know that Japan (not surprised though as they are more mature/experienced in certain areas) they still use fantastic "tool" called Mercalli.
I haven't lived in seismic areas much, but I was in central LA for both of these quakes. I was hoping for a simple Richter*distance (or d^.5, whatever may be appropriate) value to be reported. I realize that real effects are multivariate, but wouldn't that at least provide the maximum possible effects to report a magnitude-distance metric? Bc for a few million people I think the quake felt like a strong spin cycle in the next room , but we were told it was the biggest in decades.
Yeah really depends one distance and local conditions. And sometime 'micro' local conditions.
Friend of mine that lived in Oakland during the 89 earthquake mentioned seeing a 'line' of damaged buildings that snaked through a neighborhood. One or two houses on a block were wrecked. The houses across the street were also wrecked. Houses next to them were fine. Go the next street over same thing.
He thinks that line followed an old creek bed that developers filled in. So those houses were built on mud overlain with poorly compacted fill. During the earthquake the mud liquefied and sloshed around and the fill settled.
Flip side, friend in the Santa Cruz mountains a couple of miles from the epicenter. His house is built on top of a hard shale outcrop. His house suffered no damage at all.
The weakness of poor fill was also demonstrated by the collapse of row houses in the Marina district of SF.
One striking effect was the directionality of the damaging waves. Bookcases and such that were perpendicular to the waves from the hypocenter went over; those that were parallel were fine.
I think the 1906 earthquake was one or the first to be extensively scientifically documented. I've read recently that total estimated energy doesn't translate very well. California is a mass of faults and poorly consolidated rock.[1]. Apparently that dissipates the energy quickly and shaking drops off sharply with distance. Other parts of the world with large areas of solid bedrock shaking can extend for very long distances. The new Madrid earthquake was thought to be an 8+ magnitude originally. But more recent estimated put it at ~7.3.
Your assessment is incorrect. The NEIC releases two intensity maps very quickly (1) 'Did you feel it?' based on internet crowd sourcing reports And (2) 'Shake Map' from instrumental readings.
Well I didn't say they're not used, just not as much by everyday laypeople and the media. The article for this thread makes no mention, for instance, and out of the top 5 DuckDuckGo search result news articles for "ridgecrest quake" [1], only one of them contained the words "intensity" or "Mercalli". Mentions of shindo values in Japanese news are ubiquitous.
If you can don your anti-quackery bio hazard suit, the youtube channel Dutchsinse is entertaining for his forecast of earthquake locations. His guesses involve following trends along tectonic boundaries on a globe scale. One of the things I've heard him say that I've not heard elsewhere is the implied correlation between geothermal pumping operations near the latest epicenter and crust weakness. https://www.youtube.com/watch?v=Oj6Vj4TOtx4
What I found interesting about his work is the hypothesis that earthquakes are predictable based on recent nearby earthquakes. This feels like something a machine learning algorithm would have little trouble building a model of, so I'd be interested to know what sort of results people have achieved if this has been attempted before.
I can't speak to the merits of this article, but the tone is a bit sensationalist, especially the conclusion, and then they link to some commercial entities to help you prepare for doom. It makes me dismiss the entire article as a fear-mongering advertisement.
'...nothing at the ground surface had given this fault away before it fired off the quake. Some of the world’s best field geologists had scoured this area for the past 50 years...'
I live in SoCal and can't believe the amount of attention this has gotten, literally world wide. Am I underestimating the importance or is it just a slow news cycle?
I live in Corona California and an avid follower of Dutchsinse and his earthquake webcasts. I have the utmost respect for Dutch and for the support he provides on a daily basis 24/7 if he needs to. I as well as hundreds to thousands of people participate daily to be more attentive to events seismically and be prepared not scared. He has been attacked personally and ridiculed being labeled a fear monger! The information is utilized by data researching provided by the professional agencies. Dutch has our backs and provides me the knowledge to feel my safety and my family atleast have a chance of survival and what to look for. I am ashamed to say that my 57 years in california none of the agencies do anything for my safety concerns and I and many like myself feel the same way I trust Dutch and his crucial updates 1000% before considering what my officials status news conferences, broken earthquake alert app malfunctions(available Los Angeles residents only). 7.1 earthquake and Usgs site crashed and unavailable. I reside in Riverside county where shake app is not available. As far as fear-monger tactics Dutch is dedicated to what he does and is extremely gifted with having high school diploma. If you don't like what is being told to you and events surrounding you then go about your way and don't judge someone until you check it out and see his wonderful webcasts and how much he helps anybody who wants to see the truth of earth events. So Blessed to have found Michael Janitch aka DUTCHSINSE.
I live in Corona California and an avid follower of Dutchsinse and his earthquake webcasts. I have the utmost respect for Dutch and for the support he provides on a daily basis 24/7 if he needs to. I as well as hundreds to thousands of people participate daily to be more attentive to events seismically and be prepared not scared. He has been attacked personally and ridiculed being labeled a fear monger! The information is utilized by data researching provided by the professional agencies. Dutch has our backs and provides me the knowledge to feel my safety and my family atleast have a chance of survival and what to look for. I am ashamed to say that my 57 years in california none of the agencies do anything for my safety concerns and I and many like myself feel the same way I trust Dutch and his crucial updates 1000% before considering what my officials status news conferences, broken earthquake alert app malfunctions(available Los Angeles residents only). 7.1 earthquake and Usgs site crashed and unavailable. I reside in Riverside county where shake app is not available. As far as fear-monger tactics Dutch is dedicated to what he does and is extremely gifted with having high school diploma. If you don't like what is being told to you and events surrounding you then go about your way and don't judge someone until you check it out and see his wonderful webcasts and how much he helps anybody who wants to see the truth of earth events. So Blessed to have found Michael Janitch aka DUTCHSINSE.
47 comments
[ 5.4 ms ] story [ 105 ms ] thread“There was plenty of accumulated stress, enough to permit a quake with 3 m (10 ft) of slip. That suggests that one can, indeed, have aftershocks 150 years after very large mainshocks”
I looks like quakes are on a continuum. The extremes are, each quake is an individual event; on the other all quakes are a result and continuation of previous quakes. It seems like the slider position on the continuum is up to a bit of “interpretation”.
Thus, you can have multiple points of stress all linked where it’s not obvious which one is going to slip first, but they are likely to cluster over relatively short periods. Where 100 years can still be considered short.
It seems to me like we've recently (~15-30yrs) had a lot of new technology deployments (and accessibility to the underlying data that's produced) which might considerably help us with gaining an understanding over time. Things like high-resolution, high-precision aerial & satellite radar/lidar/photography and the like.
I tend to think it's just a function of time at this point, but on geological time scales that may still take quite a while I suppose.
1. Hold your hands together, palms open, as if you were praying.
2. Press them together very hard, and at the same time try to slide them past one another.
3. Predict exactly when they will slip, by how much, and how loud the sound will be. To be roughly to scale, it must be with millisecond [0] and millimeter [1] accuracy.
[0] Assuming avg. 100 years between quakes, prediction accurate to a week, avg. 5 seconds before hands slip, then 100 yrs * 52 weeks : 1 week ~ 5,000:1 ~ 5 sec : 1 msec.
[1] A 150 KM fault with a prediction of slip accurate to 0.5 M movement is 300,000:1. For a hand span of 150 mm that would equate to 0.5 um. On the other hand (pun intended), we could compare maximum slippages; assuming an earthquake movement max of 20 M and a hand slippage max of 0.2 M, a real-world resolution of 0.5 M would equate to a hand-slip prediction accurate to 2 mm.
Anything is possible, but I’m not saying we can’t or shouldn’t fight it or take steps to prevent it or mitigate damage from it. I’m saying no point in being worried about it.
(sorry there is no reply option for lots of pulp).
Isn't worry the one human emotion that actually makes us ready for things. If we had an earthquake 1000 years ago that killed half of society and the people just said, damn oh well. They don't do things the same way after that do they? They change design, learn more about the planet, adjust adjust adjust. All of that is driven by worry.
Then prediction research became the black death of academic careers with little progress.
This century a milder version called 'earthquake forecasting' has gained acceptance. That is more big data and statistical odds.
Plus 'early warning' seeks to detect quakes and warn people at the speed of light, seconds before damaging waves arrive at the speed of sound.
While the magnitude value signifies the overall energy of the quake, intensity scale values indicate the shaking intensity of a given location; hence, it feels more grounded in one's daily life experiences. Many Japanese individuals have developed an approximate sense of how strong a quake is - conversations like "That was a bit big, somewhere around shindo 4?" are common after quakes. People do of course care about magnitude, but the thing they care most about after a big quake is more likely "what was the seismic intensity in the worst-hit area?"
Any idea why intensity scales seem to be much less common in the US?
[1] https://en.wikipedia.org/wiki/Japan_Meteorological_Agency_se...
[2] https://en.wikipedia.org/wiki/Modified_Mercalli_intensity_sc...
In fact the Earthquake Early Warning's "next steps" plan says "New sensors need to be added in California to shorten the CISN sensors spacing to approximately 12 miles to facilitate timely EEW. The shorter the station spacing, the smaller the blind zone will be because warnings can be issued faster."
Check out this map comparison of the two networks: https://earthquake.usgs.gov/research/earlywarning/images/sta...
https://earthquake.usgs.gov/research/earlywarning/nextsteps....
I went to school in the LA Inland Empire area - there was a quake I felt last year there during class. It was really close but I'm pretty sure it was just short of 4.0.
We have hundreds (thousands?) of quakes per year, but the likelihood your average resident feels a quake in any given year? I think it's low.
The only time I've felt the ground shake was in the earthquake simulator at the California Academy of Science in SF :)
Friend of mine that lived in Oakland during the 89 earthquake mentioned seeing a 'line' of damaged buildings that snaked through a neighborhood. One or two houses on a block were wrecked. The houses across the street were also wrecked. Houses next to them were fine. Go the next street over same thing.
He thinks that line followed an old creek bed that developers filled in. So those houses were built on mud overlain with poorly compacted fill. During the earthquake the mud liquefied and sloshed around and the fill settled.
Flip side, friend in the Santa Cruz mountains a couple of miles from the epicenter. His house is built on top of a hard shale outcrop. His house suffered no damage at all.
One striking effect was the directionality of the damaging waves. Bookcases and such that were perpendicular to the waves from the hypocenter went over; those that were parallel were fine.
[1] https://heavy.com/news/2019/07/ridgecrest-earthquake-damage-... https://losangeles.cbslocal.com/2019/07/04/6-6m-quake-strike... https://edition.cnn.com/us/live-news/earthquake-california-j... https://www.cbsnews.com/news/ridgecrest-earthquake-aftershoc... https://www.latimes.com/local/lanow/la-me-ridgecrest-earthqu...
However Dr Stein is one of my Stanford classmates and computing earthquake stress changes for 30 years. So I would believe this study.