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I received my first and, as yet, only earthquake warning on my smart phone this past September for a 4.3 earthquake here in Southern California. It was an inte

I received my first and, as yet, only earthquake warning on my smart phone this past September for a 4.3 earthquake here in Southern California. It was an interesting fleeting experience. I was sitting on the couch, phone in hand, when it emitted an unusual fairly obnoxious noise. I glanced at the screen, saw the words earthquake and 4 something, and understood what was being conveyed sort of inchoately without making it explicit sense of it. My wife was sitting next to me reading so I turned to her and tried to show it to her but she remained absorbed in her reading. Then the room jolted, rocked a little, and settled. The nice thing about the alert is I remained relaxed the whole time. Because the alert indicated the magnitude, I wasn't too worried about damage or personal injury. Now if it had warned of a larger earthquake, like a 5 or 6, I imagine I would have been more panicked. Still, the warning would have been even more valuable in that case. It was one of the more acute "Now this feels like living in the future" moments I've had recently.

dfxm12 5y ago
I've got no idea at what magnitude I should start worrying. I would assume, and hope, that if my phone (which is otherwise on silent) is blaring, it must be a big deal. Maybe for some people a 4.3 is a big deal, but not for all...
- leeoniya 5y ago
  > I've got no idea at what magnitude I should start worrying ask your building inspector
- BurningFrog 5y ago
  You start worrying at 5.0.
  - rectang 5y ago
    It depends how close you are to the epicenter, of course. Your figure seems about right to me: I think a 5.0 near an epicenter would be pretty violent. But I've never been near an epicenter — only on the outskirts.
    - djrogers 5y ago
      It also depends on what type of ground you're on. I've been in 5+ earthquakes in a house built on solid rock (Los Angeles area hills), and a 4.5 down in the valley. Being on loose ground makes it feel much worse.
    - ryantgtg 5y ago
      Every time I feel an earthquake in LA, my first question is, “was that a small one near me or a big one far away?”
      - antod 5y ago
        You get a feel for that with the shaking frequency and/or gap between different sets of waves (P & S waves). No discernable gap and higher jerkier frequency usually means closer, a longer rolling feeling with separated phases that might last longer usually means further away. Just like sound or ocean waves the higher frequencies attenuate out quicker over distance.
- dharmab 5y ago
  If you live in an earthquake zone you quickly learn what a 2, 4, 6 feel like. It is a gossip topic in your community like the weather.
  - zinekeller 5y ago
    I think that although (estimated) magnitude is helpful, Japan's system also calculates the (estimated) intensity from the earthquake for your local area. Not always correct (but this tends to be rare), but usually within +/-1 of the Shindo scale (which is their local intensity scaling). Seems that ShakeAlert doesn't compute (yet, hopefully) the estimated intensity in your area.
  - Ancapistani 5y ago
    If you live in an area with frequent earthquakes, yes. I live near the New Madrid. There aren't frequent earthquakes here at all, but historically when we do have one... it's a big one.
  - cgriswald 5y ago
    This isn't my experience at all and I've lived in the Bay Area nearly half my life. I have a vague idea of what a mag 4 earthquake feels like, and that's about it.
    - deleted 5y ago
      [deleted]
    - antod 5y ago
      Yeah that makes sense, people talk about what magnitude x "feels" like, but they're really describing an earthquakes intensity rather than magnitude. You don't directly "feel" the magnitude. Any given magnitude quake is going to feel very different for people in different situations - eg how far away, how deep, soil conditions, how tall the building they are in etc... Magnitude is related to how much energy is released - useful for seismologists and records, while intensity is related to ground acceleration and subjective effects which is useful for structural engineers and the public caught in one. eg that 6.2 magnitude Christchurch quake mentioned elsewhere still managed to produce some of the highest ever recorded vertical ground accelerations despite releasing a tiny fraction of what a really big quake can do.
- kevinmchugh 5y ago
  Distance from the epicenter matters as well. I was 6 miles from a 4.9 last month, my first real earthquake. It was unsettling and concerning (including for the people I was on zoom with) but that was it. Nothing fell off the walls, iirc no fatalities or buildings demolished. The scale is logarithmic. My rule of thumb is that 5 is where things start to get much more dangerous.
  - Enginerrrd 5y ago
    Where I'm from, (Just a few miles from where this one was) we don't really start to worry until 7+.
- 323 5y ago
  Below 5 you only need to worry about objects in your immediate vicinity. Old/poorly built buildings start collapsing at about 6. Above 8, almost any building can collapse.
  - lostlogin 5y ago
    Christchurch, New Zealand was smashed by a 6.2. Pretty much as you say, older and poorly designed building didn’t fare well, and the earlier 7.2 earthquake wouldn’t have helped. It was a very shallow earthquake too. https://en.m.wikipedia.org/wiki/2011_Christchurch_earthquake https://en.m.wikipedia.org/wiki/2011_Christchurch_earthquake
    - quartesixte 5y ago
      Earthquake codes in California mitigate a lot of the intensity of a shake and its damage. Anecdotally, I heard to level Downtown Los Angeles completely it will have to be hit with some absurd Earthquake like a 9.0
      - njarboe 5y ago
        The strike slip fault system in most of California can produce earthquakes up to about 8.0. Subduction zone earthquakes that occur in many places, like Northern California up to Alaska, Chile, Japan, etc, can produce 9+ earthquakes. 10 and above only occur during large impact events. So California can have buildings "earthquake proofed" for much lower cost than say Seattle and they come at higher frequency. That may be one of the reasons that California's infrastructure is pretty well prepared for coming earthquakes while Seattle will have major damage when the next 9.0 hits in 0-400 years.
        jandrewrogers 5y ago
        The most dangerous fault line in Seattle, both in terms of earthquake and tsunami risk, is the eponymous system of shallow thrust faults[0] that run through the middle of the city and historically have produced ~7.0 earthquakes. Seattle buildings built in the last 3 decades are explicitly designed to survive extreme earthquakes. Most of the risk is in the 1970s and earlier infrastructure, quite a lot of which has been torn down to make room for the massive growth of Seattle. [0] https://en.wikipedia.org/wiki/Seattle_Fault https://en.wikipedia.org/wiki/Seattle_Fault
- klenwell 5y ago
  We had had an earthquake in low 5's here a couple years earlier. That was nerve-wracking but didn't do any damage. So I think I was gauging my reaction (mostly instinctively) off that. Actually, I just looked up the previous earthquake: https://earthquake.usgs.gov/earthquakes/eventpage/ci38457511/executive https://earthquake.usgs.gov/earthquakes/eventpage/ci38457511... That one was a 7.1! Significantly larger than I remembered but more distant. I must have been thinking of an earlier earthquake.
14 5y ago
This made me think one should almost practice like a fire alarm drill we do in grade schools. Set a random timer and when you get the alert react. Have it go off randomly some days so you can practice getting under a desk or in a doorway as fast as possible.
- magnusmundus 5y ago
  In the years after the disaster of 1999 [1], we used to do exactly that in Turkey in the 2000s, couple times a year. I'm not sure when/why they stopped. On a not-too-closely-related note, the last time I heard of one was in 2013, when a group of riot police forcibly dispersed a civilian drill. This was a few months after the Gezi Park protests. 1: https://en.wikipedia.org/wiki/1999_%C4%B0zmit_earthquake https://en.wikipedia.org/wiki/1999_%C4%B0zmit_earthquake
- lostlogin 5y ago
  This is done at school in New Zealand.
- FredFS456 5y ago
  Having attended grade school in BC, Canada, we used to do exactly that. Someone would come on the PA system to rattle some rocks in a jar and all students would duck under the desks until the 'earthquake' subsided, then count to 60 and quietly file out to the field.
  - aleksiy123 5y ago
    Was it actually rocks in a jar? I always thought it was some kind of recording. Completely forget about this. Thanks for the random nostalgia hit.
bschwindHN 5y ago
I was once in my old Tokyo apartment on the 12th floor. I use an early earthquake warning app. It buzzed, telling me a 9.0 occurred in Tokyo bay and I have approximately 3 seconds before the very extreme shaking starts. I just sat down and thought "welp I'm dead". It turned out to be a false alarm, triggered by something like a monitoring station being struck by lightning. I still have the screenshot of what the app looked like when it told me. Edit: found the screenshot: https://ibb.co/Lk4w5B4 https://ibb.co/Lk4w5B4
- mensetmanusman 5y ago
  Yikes, that reminds me of the false ’we are all going to be bombed soon, this is not a test’ warning the people in Hawaii got… there should be penalties for false alarms like this.
  - Enginerrrd 5y ago
    I still find the official story behind the Hawaii thing to be kind of suspect.
    - gibolt 5y ago
      Incompetent Contractors made a terrible UI and a trainee didn't understand it. Pretty clear cut failure
      - ecpottinger 5y ago
        I seen too many times when something is made by someone who understands what the system does but never thinks what a rank beginner who is suddenly facing the same display going to think. It is hard to remember what it is like for someone new to a system.
        gibolt 5y ago
        It isn't hard, it just requires active thought. Even better, get an uninitiated person and watch them try it.
codegeek 5y ago
In case this helps, I recommend registering with nixle [0] for any emergency notifications to your phone. It provides more accurate and real time details from local agencies in your area. https://www.nixle.com/ https://www.nixle.com/
AmVess 5y ago
I got my first tornado alert in last week's outburst of tornadoes in the midwest.I wasn't worried about it until the tornado sirens started going off. I became quite concerned when I saw the clouds. I'd never seen them so low and moving so fast. 24 confirmed tornadoes! Luckily, they were no where near as powerful as the ones that KY got earlier this month, but it was still alarming. And then the geniuses decided to do a test of the system yesterday at 11PM.
db65edfc7996 5y ago
Even if you had been given 60 seconds warning, what kind of mitigation can you do for a magnitude 2,4,6? Is there anything to be done if you are walking on the street/in a car/in a N floor building? I do not live in an earthquake prone region, so trying to understand the rationale. With tornadoes, theoretically you could move to a structurally sound room, but I am unsure if there is any such thing to be done for an earthquake.
- 317070 5y ago
  You are doctor and you are just about to put an injection when you get the message.
  - cutemonster 5y ago
    Or in a car: Stop the car. And indoors: - Drop down; take cover under a desk or table. - Stay away from bookcases or furniture that can fall on you. - Stay away from windows. Glass may shatter from the shakings
- russdill 5y ago
  Occasionally I need to work in the attic, on a ladder, etc. It'd be really good to know that everything around me is about to move.
- bsder 5y ago
  > what kind of mitigation can you do for a magnitude 2,4,6? Simply walk outside? If you have an empty area nearby that's an extremely safe spot to be in an earthquake. If you're in a car, get out from an underpass? A lot of deaths were due to a freeway overpass pancaking in SF. Open your garage door? This is one of the big things that is supposed to happen in California. Fire departments are supposed to have an automated system that pops the garage doors when there is an earthquake so the trucks don't get trapped by bent doors.
- rich_sasha 5y ago
  I understand you can hide under a table (won’t help if the building collapses but you won’t be whacked in the face by a bottle or bookshelf flying through the room), stand in the doorframe (these offer some protection AFAIU if the building gets damaged, or even run out into the open space.

dfxm12 5y ago

I've got no idea at what magnitude I should start worrying. I would assume, and hope, that if my phone (which is otherwise on silent) is blaring, it must be a big deal. Maybe for some people a 4.3 is a big deal, but not for all...

leeoniya 5y ago
> I've got no idea at what magnitude I should start worrying ask your building inspector
BurningFrog 5y ago
You start worrying at 5.0.
- rectang 5y ago
  It depends how close you are to the epicenter, of course. Your figure seems about right to me: I think a 5.0 near an epicenter would be pretty violent. But I've never been near an epicenter — only on the outskirts.
  - djrogers 5y ago
    It also depends on what type of ground you're on. I've been in 5+ earthquakes in a house built on solid rock (Los Angeles area hills), and a 4.5 down in the valley. Being on loose ground makes it feel much worse.
  - ryantgtg 5y ago
    Every time I feel an earthquake in LA, my first question is, “was that a small one near me or a big one far away?”
    - antod 5y ago
      You get a feel for that with the shaking frequency and/or gap between different sets of waves (P & S waves). No discernable gap and higher jerkier frequency usually means closer, a longer rolling feeling with separated phases that might last longer usually means further away. Just like sound or ocean waves the higher frequencies attenuate out quicker over distance.
dharmab 5y ago
If you live in an earthquake zone you quickly learn what a 2, 4, 6 feel like. It is a gossip topic in your community like the weather.
- zinekeller 5y ago
  I think that although (estimated) magnitude is helpful, Japan's system also calculates the (estimated) intensity from the earthquake for your local area. Not always correct (but this tends to be rare), but usually within +/-1 of the Shindo scale (which is their local intensity scaling). Seems that ShakeAlert doesn't compute (yet, hopefully) the estimated intensity in your area.
- Ancapistani 5y ago
  If you live in an area with frequent earthquakes, yes. I live near the New Madrid. There aren't frequent earthquakes here at all, but historically when we do have one... it's a big one.
- cgriswald 5y ago
  This isn't my experience at all and I've lived in the Bay Area nearly half my life. I have a vague idea of what a mag 4 earthquake feels like, and that's about it.
  - deleted 5y ago
    [deleted]
  - antod 5y ago
    Yeah that makes sense, people talk about what magnitude x "feels" like, but they're really describing an earthquakes intensity rather than magnitude. You don't directly "feel" the magnitude. Any given magnitude quake is going to feel very different for people in different situations - eg how far away, how deep, soil conditions, how tall the building they are in etc... Magnitude is related to how much energy is released - useful for seismologists and records, while intensity is related to ground acceleration and subjective effects which is useful for structural engineers and the public caught in one. eg that 6.2 magnitude Christchurch quake mentioned elsewhere still managed to produce some of the highest ever recorded vertical ground accelerations despite releasing a tiny fraction of what a really big quake can do.
kevinmchugh 5y ago
Distance from the epicenter matters as well. I was 6 miles from a 4.9 last month, my first real earthquake. It was unsettling and concerning (including for the people I was on zoom with) but that was it. Nothing fell off the walls, iirc no fatalities or buildings demolished. The scale is logarithmic. My rule of thumb is that 5 is where things start to get much more dangerous.
- Enginerrrd 5y ago
  Where I'm from, (Just a few miles from where this one was) we don't really start to worry until 7+.
323 5y ago
Below 5 you only need to worry about objects in your immediate vicinity. Old/poorly built buildings start collapsing at about 6. Above 8, almost any building can collapse.
- lostlogin 5y ago
  Christchurch, New Zealand was smashed by a 6.2. Pretty much as you say, older and poorly designed building didn’t fare well, and the earlier 7.2 earthquake wouldn’t have helped. It was a very shallow earthquake too. https://en.m.wikipedia.org/wiki/2011_Christchurch_earthquake https://en.m.wikipedia.org/wiki/2011_Christchurch_earthquake
  - quartesixte 5y ago
    Earthquake codes in California mitigate a lot of the intensity of a shake and its damage. Anecdotally, I heard to level Downtown Los Angeles completely it will have to be hit with some absurd Earthquake like a 9.0
    - njarboe 5y ago
      The strike slip fault system in most of California can produce earthquakes up to about 8.0. Subduction zone earthquakes that occur in many places, like Northern California up to Alaska, Chile, Japan, etc, can produce 9+ earthquakes. 10 and above only occur during large impact events. So California can have buildings "earthquake proofed" for much lower cost than say Seattle and they come at higher frequency. That may be one of the reasons that California's infrastructure is pretty well prepared for coming earthquakes while Seattle will have major damage when the next 9.0 hits in 0-400 years.
      - jandrewrogers 5y ago
        The most dangerous fault line in Seattle, both in terms of earthquake and tsunami risk, is the eponymous system of shallow thrust faults[0] that run through the middle of the city and historically have produced ~7.0 earthquakes. Seattle buildings built in the last 3 decades are explicitly designed to survive extreme earthquakes. Most of the risk is in the 1970s and earlier infrastructure, quite a lot of which has been torn down to make room for the massive growth of Seattle. [0] https://en.wikipedia.org/wiki/Seattle_Fault https://en.wikipedia.org/wiki/Seattle_Fault
klenwell 5y ago
We had had an earthquake in low 5's here a couple years earlier. That was nerve-wracking but didn't do any damage. So I think I was gauging my reaction (mostly instinctively) off that. Actually, I just looked up the previous earthquake: https://earthquake.usgs.gov/earthquakes/eventpage/ci38457511/executive https://earthquake.usgs.gov/earthquakes/eventpage/ci38457511... That one was a 7.1! Significantly larger than I remembered but more distant. I must have been thinking of an earlier earthquake.

14 5y ago

This made me think one should almost practice like a fire alarm drill we do in grade schools. Set a random timer and when you get the alert react. Have it go off randomly some days so you can practice getting under a desk or in a doorway as fast as possible.

magnusmundus 5y ago
In the years after the disaster of 1999 [1], we used to do exactly that in Turkey in the 2000s, couple times a year. I'm not sure when/why they stopped. On a not-too-closely-related note, the last time I heard of one was in 2013, when a group of riot police forcibly dispersed a civilian drill. This was a few months after the Gezi Park protests. 1: https://en.wikipedia.org/wiki/1999_%C4%B0zmit_earthquake https://en.wikipedia.org/wiki/1999_%C4%B0zmit_earthquake
lostlogin 5y ago
This is done at school in New Zealand.
FredFS456 5y ago
Having attended grade school in BC, Canada, we used to do exactly that. Someone would come on the PA system to rattle some rocks in a jar and all students would duck under the desks until the 'earthquake' subsided, then count to 60 and quietly file out to the field.
- aleksiy123 5y ago
  Was it actually rocks in a jar? I always thought it was some kind of recording. Completely forget about this. Thanks for the random nostalgia hit.

bschwindHN 5y ago

I was once in my old Tokyo apartment on the 12th floor. I use an early earthquake warning app. It buzzed, telling me a 9.0 occurred in Tokyo bay and I have approximately 3 seconds before the very extreme shaking starts. I just sat down and thought "welp I'm dead". It turned out to be a false alarm, triggered by something like a monitoring station being struck by lightning. I still have the screenshot of what the app looked like when it told me. Edit: found the screenshot: https://ibb.co/Lk4w5B4 https://ibb.co/Lk4w5B4

mensetmanusman 5y ago
Yikes, that reminds me of the false ’we are all going to be bombed soon, this is not a test’ warning the people in Hawaii got… there should be penalties for false alarms like this.
- Enginerrrd 5y ago
  I still find the official story behind the Hawaii thing to be kind of suspect.
  - gibolt 5y ago
    Incompetent Contractors made a terrible UI and a trainee didn't understand it. Pretty clear cut failure
    - ecpottinger 5y ago
      I seen too many times when something is made by someone who understands what the system does but never thinks what a rank beginner who is suddenly facing the same display going to think. It is hard to remember what it is like for someone new to a system.
      - gibolt 5y ago
        It isn't hard, it just requires active thought. Even better, get an uninitiated person and watch them try it.

codegeek 5y ago

In case this helps, I recommend registering with nixle [0] for any emergency notifications to your phone. It provides more accurate and real time details from local agencies in your area. https://www.nixle.com/ https://www.nixle.com/

AmVess 5y ago

I got my first tornado alert in last week's outburst of tornadoes in the midwest.I wasn't worried about it until the tornado sirens started going off. I became quite concerned when I saw the clouds. I'd never seen them so low and moving so fast. 24 confirmed tornadoes! Luckily, they were no where near as powerful as the ones that KY got earlier this month, but it was still alarming. And then the geniuses decided to do a test of the system yesterday at 11PM.

db65edfc7996 5y ago

Even if you had been given 60 seconds warning, what kind of mitigation can you do for a magnitude 2,4,6? Is there anything to be done if you are walking on the street/in a car/in a N floor building? I do not live in an earthquake prone region, so trying to understand the rationale. With tornadoes, theoretically you could move to a structurally sound room, but I am unsure if there is any such thing to be done for an earthquake.

317070 5y ago
You are doctor and you are just about to put an injection when you get the message.
- cutemonster 5y ago
  Or in a car: Stop the car. And indoors: - Drop down; take cover under a desk or table. - Stay away from bookcases or furniture that can fall on you. - Stay away from windows. Glass may shatter from the shakings
russdill 5y ago
Occasionally I need to work in the attic, on a ladder, etc. It'd be really good to know that everything around me is about to move.
bsder 5y ago
> what kind of mitigation can you do for a magnitude 2,4,6? Simply walk outside? If you have an empty area nearby that's an extremely safe spot to be in an earthquake. If you're in a car, get out from an underpass? A lot of deaths were due to a freeway overpass pancaking in SF. Open your garage door? This is one of the big things that is supposed to happen in California. Fire departments are supposed to have an automated system that pops the garage doors when there is an earthquake so the trucks don't get trapped by bent doors.
rich_sasha 5y ago
I understand you can hide under a table (won’t help if the building collapses but you won’t be whacked in the face by a bottle or bookshelf flying through the room), stand in the doorframe (these offer some protection AFAIU if the building gets damaged, or even run out into the open space.