No major tsunami is expected, local media reported initial waves were recorded as high as 40cm. The Japan Meteorological Agency forecasted up to 3m (10ft) waves.
I don't believe this earthquake is a big deal. Large earthquakes (M7.0+) happen in Japan several times a year, and given this happened in the middle of the ocean, I don't expect any major damage.
klempner•Apr 20, 2026
Yes, this is definitely only a medium deal, given that the tsunamis were mild. There is the usual concern that it might be a foreshock for a bigger quake but that's fairly unlikely.
Plenty of disruption (including a bunch of the shinkansen lines) and annoying evacuation up on the coast.
I will say that this was the longest swaying I've felt in my Kawasaki tower mansion apartment since moving here three years ago -- things were still moving about 5 minutes after it started.
pezezin•Apr 20, 2026
I live in Aomori (Northernmost prefecture of Honshu) and we got the warning before the earthquake arrived by all the cellphones in the office going crazy at the same time. It was kind of funny, because we have a lot of new guys here who have never been to Japan before and it was their first earthquake ever xD
whatsupdog•Apr 20, 2026
How much warning did you get? I mean in minutes or seconds?
asutekku•Apr 20, 2026
Depends on the location, the alert comes usually as soon as the initial tremors are registered. If you're at the epicenter, tough luck. For example, for me in Tokyo, the alert came 2 minutes before it hit, and even then, the actual earthquake was extremely subtle.
pezezin•Apr 20, 2026
In our case I guess we got the warning 10~20 seconds before the earthquake? I don't know, I didn't count it xD
asutekku•Apr 20, 2026
I use NERV, it gives you a countdown timer and i like to know whether to prepare or not
fungi•Apr 20, 2026
was reading in a park in suburban tokyo a few years ago, notifications arrived for the noto peninsula earthquake.
kids in the park stared doing wobbly knee dance :D
felt the quake about 30sec later.
pezezin•Apr 20, 2026
The one in 2024? I was in Tokyo at that time but we didn't get any notification nor felt anything :/
donw•Apr 20, 2026
This one was weird, too, like being on a boat in mildly choppy water, not a violent shake at all.
mkl•Apr 20, 2026
In my experience (NZ) that means it was strong but distant.
piazz•Apr 20, 2026
Felt it all the way in Tokyo!
There is this amazing app called NERV that, whenever there is a large earthquake anywhere in Japan, sends you an early warning push notification and an animated display with shockwaves emanating from the epicenter, plus a countdown timer for the first wave hitting you. The first it went off for me it felt like something out of sci-fi. I think I got 45 seconds this time before my apartment started shaking.
At 45 seconds, load up social media. (although I actually missed the warnings this time, was focused on work) At least assuming the number is only 7.x.
If it were 8+ or somewhat closer, I'd get under my desk. (then pull up social media on my phone)
fennecbutt•Apr 20, 2026
Standing underneath a doorframe is also advisable.
strangegecko•Apr 20, 2026
I'm pretty sure that is advice from the last millennium that is no longer taught.
Does it play appropriate Evangelion OST track depending on magnitude though?
roer•Apr 20, 2026
It is straight up the same NERV, so it might.
From the site:
> The name and logo of "NERV" are used with the explicit permission of khara Inc., the copyright holder of the "Evangelion" series, and Groundworks Corporation, which manages the rights to the series.
azath92•Apr 20, 2026
This is just the best. A very serious company, doing seriously cool and important stuff, also has an anime name/icon.
I wish more corps took themselves so lightly, while remaining serious about what they do.
mghackerlady•Apr 20, 2026
For people unfamiliar wanting an easier comparison, Evangelion is Japans star wars. It'd be like learning of tornadoes from someone with Empire insignia
Der_Einzige•Apr 20, 2026
Evangelion is so mega overrated of an anime im experiencing second hand embarrassment on behalf of Japan for letting its national personaification be exlempified by shinji.
mghackerlady•Apr 20, 2026
it is a masterpiece, up there with ghost in the shell, akira, and serial experiments lain in terms of "japanese existentialist scifi"
Der_Einzige•Apr 20, 2026
Lain is 10/10. Akira/Ghost in the Shell are great too. Evangelion is a weak 7/10 in comparison to them in every aspect imaginable. I also realized that Evangelion is Japan's version of assigning weird mysticism to religions they don't understand (much how westerners depict shinto/daoism/buddhism with tons of mysticism).
Evangelion is a disgusting anime to consider part of your national personification. Drop it and pick up Ghibli films more please Japan.
mghackerlady•Apr 20, 2026
i'll concede lain is better, but evangelion beats akira and maybe ghost in the shell. what problems do you have with it in specific?
jollyllama•Apr 20, 2026
"When it comes to the safety of this planet, it's NERV or nothin'." - ReDeath fan dub
chimeracoder•Apr 20, 2026
> Evangelion is Japans star wars
Which is funny to say because Star Wars is actually the Western version of samurai movies (especially but not exclusively Akira Kurosawa's Hidden Fortress).
That's the movie that Lucas is pretty open about heavily drawing "inspiration" from (all the way down to specific characters and plot beats) but Hidden Fortress is itself part of a larger genre of similar stories.
bombcar•Apr 20, 2026
Sadly we're stuck with companies naming themselves things like "Melchior" and "Palpatine" and somehow it's a good thing?
Anyway I need to get back to working on the Torment Nexus.
renewiltord•Apr 20, 2026
I think that’s pretty much the same. NERV uses child soldiers and is secretly planning a fused hivemind. They are the Torment Nexus.
jollyllama•Apr 20, 2026
I'm starting to like the honesty.
ricardobayes•Apr 20, 2026
A private organization delivering critical infrastructure and emergency services. Just no. Not even if it has a cutesy anime external shell. It always ends up being a race to the bottom by the nature of it.
Aboutplants•Apr 20, 2026
45 seconds is an incredible accomplishment. That’s a decent amount of heads up to get safer place. Obviously nerve wracking but great progress in alerts
strangegecko•Apr 20, 2026
Yeah. That's leagues better than what I get in Taiwan. The alert often arrives when the building is shaking or even after. I've never had a meaningful headstart.
sampullman•Apr 20, 2026
I usually get it a few seconds ahead of time at least, in Taipei. I figured it's more related to the proximity than anything else.
philistine•Apr 20, 2026
It would seem the forewarning depends a lot on the distance from the epicentre. This quake, for Tokyoites, was far enough from them that they could beat the earthquake's speed. I'm fairly certain the people on the East Coast near the quake got no notification ahead of the event.
wat10000•Apr 20, 2026
I was in a chat with people in NYC when it hit. They got advance notice, although it was just “why is everything shaking?” Followed by me going silent for a bit, so they didn’t know what was going on until it reached them.
petterroea•Apr 20, 2026
It sounds impressive but it's worth considering that this was a large quake that was felt by basically half of the country. You do not get this much warning if you are anywhere near where damage happens.
The 45 seconds is better thought of as the time it takes for the quake to propagate to Tokyo
Tor3•Apr 20, 2026
I didn't feel a thing a bit south of Nagoya. Almost strange that there was nothing here, when you got shaking in Tokyo.
bell-cot•Apr 20, 2026
> Felt it all the way in Tokyo!
How many stories above the ground, and might you guess at your building's construction (wood frame, steel frame, etc.) and foundations (on bedrock, on loose sediments, etc.)?
Xenoamorphous•Apr 20, 2026
Receiving one of those sounds really scary.
ricardobayes•Apr 20, 2026
Hmm, why does this needs to be an app and not the built-in alert notification system? Outsourcing critical infrastructure and emergency services to private parties is always a terrible idea.
pamcake•Apr 20, 2026
> Outsourcing critical infrastructure and emergency services to private parties is always a terrible idea.
That would include Apple and Google.
jandrewrogers•Apr 20, 2026
In many countries the authority and capability to send alerts is relatively decentralized and/or they require people to be inserted in the decision loop. Things are this way for policy and jurisdictional reasons. To change it you'd need to redesign the bureaucracy and authority, including many parts that have nothing to do with emergency services. Those changes are not going to happen.
Under these constraints it is effectively impossible to send automated alerts at scale with low latency as demonstrated here. A private app does not operate under such constraints.
swang•Apr 20, 2026
An Earthquake happened in SF recently where I got a push notification from Apple/iOS and I felt it maybe 5-10 seconds later. Nothing fancy though just a notification. I'm guessing it's not on for Japan? Seems like this app shows way more.
klausa•Apr 20, 2026
For big enough quakes you get notification from the government (a VERY loud and specific one too, being in public and hearing _everyones_ phones suddenly go off is... mildly terrifying) too; but they're so frequent and (usually) non-super-threatening that they don't get sent out for _every_ quake.
thomascountz•Apr 20, 2026
Ruby Kaigi[1] starts soon in Hakodate, across the Tsugaru Strait in southern Hokkaido, ~200–250 km away. I hope everyone stays safe.[2]
I live in Tokyo. Today's quake felt pretty strong (maybe because I was on the 14th floor) and lasted a while. Haven't felt one this big in months.
vaylian•Apr 20, 2026
How long do these earthquakes typically take until they are over?
left-struck•Apr 20, 2026
I’m Chiba so pretty far away from this one, and in this case it was like a real low frequency swaying that lasted maybe 3 minutes or so.
In the past there were small earthquakes closer to me that felt like quite a violent bump followed by higher frequency vibrations, but less than a minute. Those earthquakes were much smaller though, like magnitude 4.
kccqzy•Apr 20, 2026
> The 1989 earthquake in Loma Prieta, California, which killed sixty-three people and caused six billion dollars’ worth of damage, lasted about fifteen seconds and had a magnitude of 6.9. A thirty-second earthquake generally has a magnitude in the mid-sevens. A minute-long quake is in the high sevens, a two-minute quake has entered the eights, and a three-minute quake is in the high eights. By four minutes, an earthquake has hit magnitude 9.0.
budududuroiu•Apr 20, 2026
Was in Tokyo today, if I didn't see the news, I wouldn't have noticed there even was an earthquake.
Surprised others said they felt it.
jhatax•Apr 20, 2026
Didn’t feel it either, and my family and I are close to Shirokanedai. I hope folks are fine where this was felt more than what I experienced.
9 Comments
No major tsunami is expected, local media reported initial waves were recorded as high as 40cm. The Japan Meteorological Agency forecasted up to 3m (10ft) waves.
I don't believe this earthquake is a big deal. Large earthquakes (M7.0+) happen in Japan several times a year, and given this happened in the middle of the ocean, I don't expect any major damage.
Plenty of disruption (including a bunch of the shinkansen lines) and annoying evacuation up on the coast.
I will say that this was the longest swaying I've felt in my Kawasaki tower mansion apartment since moving here three years ago -- things were still moving about 5 minutes after it started.
kids in the park stared doing wobbly knee dance :D
felt the quake about 30sec later.
There is this amazing app called NERV that, whenever there is a large earthquake anywhere in Japan, sends you an early warning push notification and an animated display with shockwaves emanating from the epicenter, plus a countdown timer for the first wave hitting you. The first it went off for me it felt like something out of sci-fi. I think I got 45 seconds this time before my apartment started shaking.
https://nerv.app/en/
For me I always just turn on iPhone screen recording and marvel at this amazing app and wish we had something like this in California.
https://apps.apple.com/us/app/myshake-earthquake-alerts/id14...
If it were 8+ or somewhat closer, I'd get under my desk. (then pull up social media on my phone)
Does it play appropriate Evangelion OST track depending on magnitude though?
From the site:
> The name and logo of "NERV" are used with the explicit permission of khara Inc., the copyright holder of the "Evangelion" series, and Groundworks Corporation, which manages the rights to the series.
I wish more corps took themselves so lightly, while remaining serious about what they do.
Evangelion is a disgusting anime to consider part of your national personification. Drop it and pick up Ghibli films more please Japan.
Which is funny to say because Star Wars is actually the Western version of samurai movies (especially but not exclusively Akira Kurosawa's Hidden Fortress).
That's the movie that Lucas is pretty open about heavily drawing "inspiration" from (all the way down to specific characters and plot beats) but Hidden Fortress is itself part of a larger genre of similar stories.
Anyway I need to get back to working on the Torment Nexus.
The 45 seconds is better thought of as the time it takes for the quake to propagate to Tokyo
How many stories above the ground, and might you guess at your building's construction (wood frame, steel frame, etc.) and foundations (on bedrock, on loose sediments, etc.)?
That would include Apple and Google.
Under these constraints it is effectively impossible to send automated alerts at scale with low latency as demonstrated here. A private app does not operate under such constraints.
[1]: https://rubykaigi.org/2026/
[2]: https://www.japan.travel/en/japan-safe-travel-information/ts...
https://en.wikipedia.org/wiki/Moment_magnitude_scale
In the past there were small earthquakes closer to me that felt like quite a violent bump followed by higher frequency vibrations, but less than a minute. Those earthquakes were much smaller though, like magnitude 4.
Surprised others said they felt it.