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Tsunami Warning for Northern California

tsunami.gov

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Re: Tsunami Warning for Northern California

#121

Post by crazygringo »

teaearlgraycold wrote: post #89
cossatot wrote: post #68

Based on the location and focal mechanism of the earthquake ( https://earthquake.usgs.gov/earthquakes/eventpage/nc75095651... ), this is a strike-slip earthquake on the plate boundary between the Pacific and Gorda/Juan de Fuca plates. Strike-slip earthquakes occur when two plates slide beside each other during an earthquake, usually along a steeply-dipping if not vertical fault. These kinds of earthquakes almost neve…

The system is training me to ignore it already. I’m in SF and we had a flash flood emergency alert. I never heard of or saw any floods. I could believe a street or two might have had a few inches of water at most. But honestly I’d bet against even that. And then there’s this tsunami alert today.

Flash floods depend on your elevation.

I've gotten the warning and my street is perfectly fine... and then I look at social media and cars on the street are half-submerged just 20 blocks away.

You might not even be aware of elevation differences when they're gradual.

Re: Tsunami Warning for Northern California

#123

Post by toast0 »

dylan604 wrote: post #112
mgsouth wrote: post #98

Earlier quoted context omitted.

It varies, a lot, and depends upon a lot of things. I'm not current on all the current details, but many moons ago was involved in push notification development. * Notification path. IoS at the time was pretty protective of the user's battery, and had specific services you had to use. I imagine there's special treatment now for emergency communications. * Phone state. How deeply asleep is it? Are there other backgrou…

> a three-letter acronym with an ampersand in the middle wasn't the official name switched to no longer use that ampersand so it is just the three letters now (and for some time)?

I believe they did announce that, and also claim that the letters no longer mean anything (which makes sense as telegraph is long dead, and the telephone network is primarily spam), however their website including investor relations has the ampersand everywhere, so maybe they backpedaled.

Or maybe ampersand was dropped before SBC bought the remaining parts of the old business and reformed T-1000 with the ampersand?

Re: Tsunami Warning for Northern California

#124

Post by numpad0 »

Rebelgecko wrote: post #100
numpad0 wrote: post #74

Earlier quoted context omitted.

LTE ETWS/PWS is mandatory feature, iPhones has the same thing. Maybe you've explicitly disabled it, considering (IIUC) US used it for AMBER alerts and had annoyed lots of people at some point. Generally an earthquake warnings are issued by someone always automatically correlating sensors everywhere, USGS and/or NOAA in case with US, and then cellular carriers broadcasting the alert through LTE feature. This does not…

The wireless emergency alerts (like what you see for amber alerts) that go over cell towers have pretty high latency (IIRC on the order of a minute or two for the alert to disseminate). The native Android earthquake alerts are much faster

Carrier alerts is the fastest. Not only the whole process from detecting tremors to alerts take 30 seconds or so, there aren't other data sources than what those carriers use anyway, so there's just no way Google can be faster than carriers.

PWS is also a broadcast, meaning the phones don't have to wait for cellular timeslots, so it's faster and bandwidth efficient in that regard too.

Re: Tsunami Warning for Northern California

#125

Post by sib »

teaearlgraycold wrote: post #89
cossatot wrote: post #68

Based on the location and focal mechanism of the earthquake ( https://earthquake.usgs.gov/earthquakes/eventpage/nc75095651... ), this is a strike-slip earthquake on the plate boundary between the Pacific and Gorda/Juan de Fuca plates. Strike-slip earthquakes occur when two plates slide beside each other during an earthquake, usually along a steeply-dipping if not vertical fault. These kinds of earthquakes almost neve…

The system is training me to ignore it already. I’m in SF and we had a flash flood emergency alert. I never heard of or saw any floods. I could believe a street or two might have had a few inches of water at most. But honestly I’d bet against even that. And then there’s this tsunami alert today.

This is similar to the "severe weather alert" I just received on my phone when the temperature will range from 47' to 67' F (8' to 19' C) in Los Angeles today, December 5, with clear, sunny skies and no noticeable winds.

Of course, when I tap on the notification and open the app, I see that it's actually driven by an air quality alert because the AQI will be 112 (which isn't even that high.)

Come on guys - the dictionary defines weather as, "the state of the atmosphere with respect to heat or cold, wetness or dryness, calm or storm, clearness or cloudiness."

Re: Tsunami Warning for Northern California

#126

Post by sib »

mgsouth wrote: post #110
numpad0 wrote: post #74

Earlier quoted context omitted.

LTE ETWS/PWS is mandatory feature, iPhones has the same thing. Maybe you've explicitly disabled it, considering (IIUC) US used it for AMBER alerts and had annoyed lots of people at some point. Generally an earthquake warnings are issued by someone always automatically correlating sensors everywhere, USGS and/or NOAA in case with US, and then cellular carriers broadcasting the alert through LTE feature. This does not…

For folks jumping on saying "that's not a carrier thing". All comms are a carrier thing. Whether it's ETWS, SMS, or IP, it's going through the carrier, they process it, and they do extensive traffic management. Carriers absolutely can and will inspect, proxy, aggregate, and do anything else that will tease out another few % of "free" capacity. [Edit:] All too real scenario: Carrier knows about particular IP addresses…

In this case, there is a separate service that Google developed for early warning.

(Source, worked at Google in Android team.)

Re: Tsunami Warning for Northern California

#127

Post by toast0 »

bagels wrote: post #88

They should really name these like storms/tornados: "warning" means there is actually a tsunami, "watch" means there might be a tsunami. The map showed the warning extending to >1000ft elevation. That is a little over the top.

The ever present taco distinction.

https://www.stevenscountywa.gov/pview.aspx?id=21417&catid=0

Re: Tsunami Warning for Northern California

#128

Post by dragonwriter »

duxup wrote: post #8

How do Tsunami Warnings work? For a Midwesterner a Tornado Warning requires someone to see it, or be be detected by radar. It's usually a good indicator that it is highly likely that the tornado exists and it is actively doing its thing somewhere. Warnings are pretty specific and almost always involve the thing happening. Tsunami though, would it have to exist as far as seeing it on the coast, or is this more of a "c…

https://tsunami.gov/?page=message_definitions

A warning, the highest level, means “a tsunami with the potential to generate widespread inundation is imminent, expected, or occurring.”

The actual criteria are here:

https://tsunami.gov/operations/opsmanual.pdf (Section 3)

Note that the level of initial alert for an area is influenced by both the magnitude of the quake and the distance/time from quake to the area the alert covers.

> I wonder if the Tsunami situation with all the under water variables is a lot more unknown?

Yeah,I don't think there is anything as clear and with the coverage of radar for tsunamis, and warning when you see one is going to be too late.

Re: Tsunami Warning for Northern California

#129

Post by sparky_z »

wooten wrote: post #114

Two observations: 1) The blanket warning for areas that are clearly outside inundation zones drives a lot of confusion/fear. We can vastly improve our warning infra by utilizing better geo data to drive more effective alerts. For example, Tsunami inundation zone data is well known. Why not send only to phones currently in and maybe within 250m of those zones? 2) A lot of 'am I in a tsunami inundation zone?' sites wer…

>Why not send only to phones currently in and maybe within 250m of those zones?

There's often significant lag between the earthquake and the arrival time. You don't just want the people in the inundation zone to know, you also want everyone else to know to stay away.

That's not just a theoretical edge case. If this had been a major tsunami your system would have killed me just now. I would have been outside of your suggested range and alone at the time of the alert, but was planning to walk my dog along the water front at noon, which was just around the projected arrival time.

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