> “We got some reports from folks that they got up to 10 seconds’ warning before they felt shaking. That’s pretty darn good,” said Robert de Groot, a ShakeAlert coordinator with the USGS.
Fun fact: that's three times longer than it takes to safely trip a nuclear reactor: "A reactor trip causes all the control rods to insert into the reactor core, and shut down the plant in a very short time (about three seconds)." https://public-blog.nrc-gateway.gov/2012/12/28/what-is-a-rea...
I mention this because this quake's epicenter is pretty close to the Humboldt Bay NGS, and there's always a lot of uninformed hand-wringing about atomic energy near fault lines (even though this particular station has been offline since 1988) https://en.wikipedia.org/wiki/Humboldt_Bay_Nuclear_Power_Pla...
It's also worth noting that, in the case of the Fukushima accident, all nuclear reactors shutdown correctly when the earthquake was detected, before it reached the plants. All of them, including the affected plant, shutdown as designed. Then the tsunami came and created a bunch of issues (lots of vital equipment at ground level, generator trucks came and were incompatible, yada yada yada).
Japan has a great early warning system for both earthquakes and tsunamis that has been in operation for quite a while now(since 2007?)
I'm a nuke proponent but it's very worth pointing out that a nuclear reactor that has been recently shutdown will need days of cooling to be available in order to safely avoid damage to the reactor and potential meltdown, pressure spikes, etc.
New-ish designs can do the cooling completely passively but not all active nuclear reactors are so equipped (Fukushima's Daiichi's ancient BWR design needed active cooling, which failed in the tsunami, while the slightly newer BWR design at Fukushima Daini survived the tsunami damage without further core damage).
Is that why Chernobyl reactor core kept burning after the blowup? I am not familiar with cycle of the nuclear core in the plant. I assumed once the control rod is in, the core will stop "combusting"?
The very short story is that unlike with something like gasoline combustion, where the energy output basically happens nearly instantaneously, a nuclear fission event releases energy both directly (from the fissioning) and indirectly (from the subsequent radioactive decay of the fission products).
This indirect energy output is small in comparison to the reactor's output, but a small percentage times a very large power output is still sufficient to meltdown a reactor (and boil away the coolant in the process) if there's no way to remove the heat being generated.
Imagine what you'd have to do with a car engine if every car trip of 4 hours or more produced 4% power output in the form of heat for the next day after your trip was over.
Once the control rods are in, the reactor is losing more energy than it is producing and will eventually cool down. However in many old (e.g. 60's era) designs including Chernobyl and Fukushima, the reactor is losing that heat via active water cooling. If you turn off those heat pumps, then the core is still energy-positive even with rods inserted.
In Chernobyl the core literally blew up, so it's a different situation. But in Fukushima the pumps lost power and so even though the control rods were fully inserted, there was a real risk it might get hot enough to melt down anyway. That was thankfully avoided.
Reactor designs differ, and they tend to have a large number of emergency backup and contingency plans. Here's a decent overview for a typical reactor: https://interestingengineering.com/nuclear-meltdown-what-wou... (scroll down to "Preventing a nuclear meltdown").
TL;DR: the control rods slow the reaction, but the fuel rods are still hot, and the space is enclosed (to prevent radioactive material from casually escaping) so it gets hotter and hotter without intervention. If the fuel rods get hot enough they start melting, which produces hydrogen, which can explode.
Fun fact: that's three times longer than it takes to safely trip a nuclear reactor: "A reactor trip causes all the control rods to insert into the reactor core, and shut down the plant in a very short time (about three seconds)." https://public-blog.nrc-gateway.gov/2012/12/28/what-is-a-rea...
I mention this because this quake's epicenter is pretty close to the Humboldt Bay NGS, and there's always a lot of uninformed hand-wringing about atomic energy near fault lines (even though this particular station has been offline since 1988) https://en.wikipedia.org/wiki/Humboldt_Bay_Nuclear_Power_Pla...